Uniapp wechat applet realizes the function of connecting low-power Bluetooth printing

Wechat applet project uses Bluetooth connection printing , I made a reference note by referring to the official documents , When using this method, follow the steps to check .

uni-app Bluetooth connectivity

bluetooth ：

1、 Initialize Bluetooth

uni.openBluetoothAdapter(OBJECT)

uni.openBluetoothAdapter({
    
  success(res) {
    
    console.log(res)
    //  Interface calls the successful callback function 
  },
  fail:(res)=>{
    
      //  Interface call failed callback function 
  },
  complete:()=>{
    
	//  The callback function at the end of the interface call （ Successful call 、 Failure will be carried out ）
  }
})

error ：res.errCode

Error code	error message	explain
0	ok	normal
10000	not init	Bluetooth adapter not initialized
10001	not available	The Bluetooth adapter is currently unavailable
10002	no device	The specified device was not found
10003	connection fail	The connection fails
10004	no service	The specified service was not found
10005	no characteristic	The specified characteristic value... Was not found
10006	no connection	The current connection has been disconnected
10007	property not support	The current eigenvalue does not support this operation
10008	system error	All other exceptions reported by the system
10009	system not support	Android System specific , The system version is lower than 4.3 I won't support it BLE

Be careful

• Other Bluetooth related API Must be in uni.openBluetoothAdapter Use after call . otherwise API Will return an error （errCode=10000）.
• When the user's Bluetooth switch is not turned on or the mobile phone does not support Bluetooth , call uni.openBluetoothAdapter Will return an error （errCode=10001）, Indicates that the Bluetooth function of the mobile phone is not available . here APP Bluetooth module has been initialized , It can be done by uni.onBluetoothAdapterStateChange Monitor the change of Bluetooth status of mobile phone , You can also call all of the Bluetooth module API.

2、 Monitor Bluetooth adapter status change events

uni.onBluetoothAdapterStateChange(CALLBACK)

CALLBACK Returns the parameter

attribute	type	explain
available	boolean	Whether the Bluetooth adapter is available
discovering	boolean	Whether the Bluetooth adapter is in search state

Sample code

uni.onBluetoothAdapterStateChange((res) => {
    
    console.log('onBluetoothAdapterStateChange', res)
    // available： Whether the Bluetooth adapter is available 
    if (res.available) {
    
        //  Cancel monitoring , otherwise stopBluetoothDevicesDiscovery It will continue to trigger onBluetoothAdapterStateChange,
        //  Cause to call again startBluetoothDevicesDiscovery
        uni.onBluetoothAdapterStateChange(() => {
    });
        //  Start searching for Bluetooth peripherals nearby 
        uni.startBluetoothDevicesDiscovery(OBJECT)
    }
})

3、 Start searching for Bluetooth peripherals nearby

uni.startBluetoothDevicesDiscovery(OBJECT)

This operation consumes system resources , Please call after searching and connecting to device uni.stopBluetoothDevicesDiscovery Method to stop searching .

OBJECT Parameter description

attribute	type	The default value is	Required	explain
services	Array		no	To search but Bluetooth device owner service Of uuid list . Some Bluetooth devices broadcast their masters service Of uuid. If this parameter is set , Then only the broadcast packet with corresponding uuid The main service of Bluetooth device . It is recommended to filter out other Bluetooth devices that do not need to be processed around mainly through this parameter .
allowDuplicatesKey	boolean	false	no	Whether it is allowed to report the same equipment repeatedly . If repeated reporting is allowed , be uni.onBlueToothDeviceFound Method will report the same device multiple times , however RSSI Values will vary .
interval	number	0	no	Report the interval of the equipment .0 It means that new equipment is found and reported immediately , Other values are reported according to the incoming interval .
success	function		no	Interface calls the successful callback function
fail	function		no	Interface call failed callback function
complete	function		no	The callback function at the end of the interface call （ Successful call 、 Failure will be carried out ）

error

Error code	error message	explain
0	ok	normal
10000	not init	Bluetooth adapter not initialized
10001	not available	The Bluetooth adapter is currently unavailable
10002	no device	The specified device was not found
10003	connection fail	The connection fails
10004	no service	The specified service was not found
10005	no characteristic	The specified characteristic value... Was not found
10006	no connection	The current connection has been disconnected
10007	property not support	The current eigenvalue does not support this operation
10008	system error	All other exceptions reported by the system
10009	system not support	Android System specific , The system version is lower than 4.3 I won't support it BLE

Be careful ：

• App The client currently only supports discovery ble Bluetooth devices , More Bluetooth device discovery , have access to Native.js, Reference resources ：https://ask.dcloud.net.cn/article/114. It can also be obtained in the plug-in market Native plug-ins

Sample code

//  Take the Bluetooth smart light of wechat hardware platform as an example , Main service  UUID  yes  FEE7. Pass in this parameter , Search only the main service  UUID  by  FEE7  The equipment 
uni.startBluetoothDevicesDiscovery({
    
  services: ['FEE7'],
  success(res) {
    
    console.log(res)
    //  Listen for events that find new devices 
    uni.onBluetoothDeviceFound(OBJECT)
  }
})

4、 Listen for events that find new devices

uni.onBluetoothDeviceFound(CALLBACK)

CALLBACK Returns the parameter

attribute	type	explain
devices	Array	List of newly searched devices

devices Structure

attribute	type	explain
name	string	Bluetooth device name , Some devices may not
deviceId	string	Used to distinguish between devices id
RSSI	number	Current signal strength of Bluetooth devices
advertisData	ArrayBuffer	In the broadcast data segment of the current Bluetooth device ManufacturerData Data segment .
advertisServiceUUIDs	Array	In the broadcast data segment of the current Bluetooth device ServiceUUIDs Data segment
localName	string	In the broadcast data segment of the current Bluetooth device LocalName Data segment
serviceData	Object	In the broadcast data segment of the current Bluetooth device ServiceData Data segment

Be careful

• If in uni.onBluetoothDeviceFound Called back a device , This device will be added to uni.getBluetoothDevices The array obtained by the interface .

Sample code

// ArrayBuffer turn 16 Example progress string 
function ab2hex(buffer) {
    
  const hexArr = Array.prototype.map.call(
    new Uint8Array(buffer),
    function (bit) {
    
      return ('00' + bit.toString(16)).slice(-2)
    }
  )
  return hexArr.join('')
}
uni.onBluetoothDeviceFound(function (devices) {
    
  console.log('new device list has founded')
  console.dir(devices)
  console.log(ab2hex(devices[0].advertisData))
})

5、 Stop searching for nearby Bluetooth peripherals

uni.stopBluetoothDevicesDiscovery(OBJECT)

If you have found the required Bluetooth device and do not need to continue searching , It is recommended to call this interface to stop Bluetooth search .

OBJECT Parameter description

attribute	type	The default value is	Required	explain
success	function		no	Interface calls the successful callback function
fail	function		no	Interface call failed callback function
complete	function		no	The callback function at the end of the interface call （ Successful call 、 Failure will be carried out ）

error

Error code	error message	explain
0	ok	normal
10000	not init	Bluetooth adapter not initialized
10001	not available	The Bluetooth adapter is currently unavailable
10002	no device	The specified device was not found
10003	connection fail	The connection fails
10004	no service	The specified service was not found
10005	no characteristic	The specified characteristic value... Was not found
10006	no connection	The current connection has been disconnected
10007	property not support	The current eigenvalue does not support this operation
10008	system error	All other exceptions reported by the system
10009	system not support	Android System specific , The system version is lower than 4.3 I won't support it BLE

Sample code

uni.stopBluetoothDevicesDiscovery({
    
  success(res) {
    
    console.log(res)
  }
})

6、 according to uuid Get the connected device

uni.getConnectedBluetoothDevices(OBJECT)

OBJECT Parameter description

attribute	type	The default value is	Required	explain
services	Array		yes	Bluetooth device owner service Of uuid list
success	function		no	Interface calls the successful callback function
fail	function		no	Interface call failed callback function
complete	function		no	The callback function at the end of the interface call （ Successful call 、 Failure will be carried out ）

success Return parameter description ：

attribute	type	explain
devices	Array	List of devices searched

res.devices Structure

attribute	type	explain
name	string	Bluetooth device name , Some devices may not
deviceId	string	Used to distinguish between devices id

error

Error code	error message	explain
0	ok	normal
10000	not init	Bluetooth adapter not initialized
10001	not available	The Bluetooth adapter is currently unavailable
10002	no device	The specified device was not found
10003	connection fail	The connection fails
10004	no service	The specified service was not found
10005	no characteristic	The specified characteristic value... Was not found
10006	no connection	The current connection has been disconnected
10007	property not support	The current eigenvalue does not support this operation
10008	system error	All other exceptions reported by the system
10009	system not support	Android System specific , The system version is lower than 4.3 I won't support it BLE

Sample code

uni.getConnectedBluetoothDevices({
    
  success(res) {
    
    console.log(res)
  }
})

7、 Get all Bluetooth devices discovered during the Bluetooth module takes effect

uni.getBluetoothDevices(OBJECT)

Including devices already connected to the machine .

OBJECT Parameter description

attribute	type	The default value is	Required	explain
success	function		no	Interface calls the successful callback function
fail	function		no	Interface call failed callback function
complete	function		no	The callback function at the end of the interface call （ Successful call 、 Failure will be carried out ）

success Return parameter description ：

attribute	type	explain
devices	Array	uuid Corresponding list of connected devices

res.devices Structure

attribute	type	explain
name	string	Bluetooth device name , Some devices may not
deviceId	string	Used to distinguish between devices id
RSSI	number	Current signal strength of Bluetooth devices
advertisData	ArrayBuffer	In the broadcast data segment of the current Bluetooth device ManufacturerData Data segment .
advertisServiceUUIDs	Array	In the broadcast data segment of the current Bluetooth device ServiceUUIDs Data segment
localName	string	In the broadcast data segment of the current Bluetooth device LocalName Data segment
serviceData	Object	In the broadcast data segment of the current Bluetooth device ServiceData Data segment

error

Error code	error message	explain
0	ok	normal
10000	not init	Bluetooth adapter not initialized
10001	not available	The Bluetooth adapter is currently unavailable
10002	no device	The specified device was not found
10003	connection fail	The connection fails
10004	no service	The specified service was not found
10005	no characteristic	The specified characteristic value... Was not found
10006	no connection	The current connection has been disconnected
10007	property not support	The current eigenvalue does not support this operation
10008	system error	All other exceptions reported by the system
10009	system not support	Android System specific , The system version is lower than 4.3 I won't support it BLE

Sample code

// ArrayBuffer turn 16 Example progress string 
function ab2hex(buffer) {
    
  const hexArr = Array.prototype.map.call(
    new Uint8Array(buffer),
    function (bit) {
    
      return ('00' + bit.toString(16)).slice(-2)
    }
  )
  return hexArr.join('')
}
uni.getBluetoothDevices({
    
  success(res) {
    
    console.log(res)
    if (res.devices[0]) {
    
      console.log(ab2hex(res.devices[0].advertisData))
    }
  }
})

Be careful

• The device list obtained by this interface is All Bluetooth devices searched during the validity of Bluetooth module , If the Bluetooth module is not called in time after the use process uni.closeBluetoothAdapter Release resources , There will be Bluetooth devices found in the previous Bluetooth usage process when calling this interface , Maybe the device is no longer around the user , Unable to connect .
• When the Bluetooth device is searched , The system returned name The fields are generally LocalName Device name in the field , If you establish a connection with a Bluetooth device , The system returned name The field will be changed to that obtained from the Bluetooth device GattName. If you need to dynamically change the device name and display , It is recommended to use localName Field .

8、 Get the status of the native Bluetooth adapter

uni.getBluetoothAdapterState(OBJECT)

OBJECT Parameter description

attribute	type	The default value is	Required	explain
success	function		no	Interface calls the successful callback function
fail	function		no	Interface call failed callback function
complete	function		no	The callback function at the end of the interface call （ Successful call 、 Failure will be carried out ）

success Return parameter description ：

attribute	type	explain
discovering	boolean	Are you searching for devices
available	boolean	Whether the Bluetooth adapter is available

error

Error code	error message	explain
0	ok	normal
10000	not init	Bluetooth adapter not initialized
10001	not available	The Bluetooth adapter is currently unavailable
10002	no device	The specified device was not found
10003	connection fail	The connection fails
10004	no service	The specified service was not found
10005	no characteristic	The specified characteristic value... Was not found
10006	no connection	The current connection has been disconnected
10007	property not support	The current eigenvalue does not support this operation
10008	system error	All other exceptions reported by the system
10009	system not support	Android System specific , The system version is lower than 4.3 I won't support it BLE

Sample code

uni.getBluetoothAdapterState({
    
  success(res) {
    
    console.log(res)
  }
})

9、 Turn off the Bluetooth module

uni.closeBluetoothAdapter(OBJECT)

Calling this method will disconnect all established connections and release system resources . It is recommended to use Bluetooth process , And uni.openBluetoothAdapter Call in pairs .

OBJECT Parameter description

attribute	type	The default value is	Required	explain
success	function		no	Interface calls the successful callback function
fail	function		no	Interface call failed callback function
complete	function		no	The callback function at the end of the interface call （ Successful call 、 Failure will be carried out ）

error

Error code	error message	explain
0	ok	normal
10000	not init	Bluetooth adapter not initialized
10001	not available	The Bluetooth adapter is currently unavailable
10002	no device	The specified device was not found
10003	connection fail	The connection fails
10004	no service	The specified service was not found
10005	no characteristic	The specified characteristic value... Was not found
10006	no connection	The current connection has been disconnected
10007	property not support	The current eigenvalue does not support this operation
10008	system error	All other exceptions reported by the system
10009	system not support	Android System specific , The system version is lower than 4.3 I won't support it BLE

Sample code

uni.closeBluetoothAdapter({
    
  success(res) {
    
    console.log(res)
  }
})

Low power Bluetooth ：

1、 Set the Bluetooth maximum transmission unit

[uni.setBLEMTU(OBJECT)

Need to be in uni.createBLEConnection After the call succeeds, call ,mtu set range (22,512). Android 5.1 The above is effective .

OBJECT Parameter description

attribute	type	The default value is	Required	explain
deviceId	string		yes	Used to distinguish between devices id
mtu	number		yes	Maximum transmission unit (22,512) Within the interval , Company bytes
success	function		no	Interface calls the successful callback function
fail	function		no	Interface call failed callback function
complete	function		no	The callback function at the end of the interface call （ Successful call 、 Failure will be carried out ）

2、 Write binary data to the characteristic value of low-power Bluetooth device

uni.writeBLECharacteristicValue(OBJECT)

Be careful ： The eigenvalue of the device must support write To successfully call .

OBJECT Parameter description

attribute	type	The default value is	Required	explain
deviceId	string		yes	Bluetooth devices id
serviceId	string		yes	The Bluetooth eigenvalue corresponds to the service uuid
characteristicId	string		yes	Bluetooth eigenvalue uuid
value	ArrayBuffer		yes	The binary value corresponding to the characteristic value of the Bluetooth device
success	function		no	Interface calls the successful callback function
fail	function		no	Interface call failed callback function
complete	function		no	The callback function at the end of the interface call （ Successful call 、 Failure will be carried out ）

error

Error code	error message	explain
0	ok	normal
10000	not init	Bluetooth adapter not initialized
10001	not available	The Bluetooth adapter is currently unavailable
10002	no device	The specified device was not found
10003	connection fail	The connection fails
10004	no service	The specified service was not found
10005	no characteristic	The specified characteristic value... Was not found
10006	no connection	The current connection has been disconnected
10007	property not support	The current eigenvalue does not support this operation
10008	system error	All other exceptions reported by the system
10009	system not support	Android System specific , The system version is lower than 4.3 I won't support it BLE

Be careful

• There is a possibility of write failure when parallel calls are repeated .
• APP There is no limit on the write packet size , However, the system and Bluetooth devices will restrict Bluetooth 4.0 The data size of a single transmission , A write error occurs when the maximum number of bytes is exceeded , It is recommended that no more than... Be written each time 20 byte .
• If the single write data is too long ,iOS There will be no callback on the system （ Including error callback ）.
• On the Android platform , Calling notifyBLECharacteristicValueChange Call... Immediately after success writeBLECharacteristicValue Interface , On some models 10008 System error

Sample code

//  Send a 0x00 Of 16 Hexadecimal data 
const buffer = new ArrayBuffer(1)
const dataView = new DataView(buffer)
dataView.setUint8(0, 0)
uni.writeBLECharacteristicValue({
    
  //  there  deviceId  Need to be in  getBluetoothDevices  or  onBluetoothDeviceFound  Interface 
  deviceId,
  //  there  serviceId  Need to be in  getBLEDeviceServices  Interface 
  serviceId,
  //  there  characteristicId  Need to be in  getBLEDeviceCharacteristics  Interface 
  characteristicId,
  //  there value yes ArrayBuffer type 
  value: buffer,
  success(res) {
    
    console.log('writeBLECharacteristicValue success', res.errMsg)
  }
})

3、 Read the binary data value of the characteristic value of Low Power Bluetooth device

uni.readBLECharacteristicValue(OBJECT)

Be careful ： The eigenvalue of the device must support read To successfully call .

OBJECT Parameter description

attribute	type	The default value is	Required	explain
deviceId	string		yes	Bluetooth devices id
serviceId	string		yes	The Bluetooth eigenvalue corresponds to the service uuid
characteristicId	string		yes	Bluetooth eigenvalue uuid
success	function		no	Interface calls the successful callback function
fail	function		no	Interface call failed callback function
complete	function		no	The callback function at the end of the interface call （ Successful call 、 Failure will be carried out ）

error

Error code	error message	explain
0	ok	normal
10000	not init	Bluetooth adapter not initialized
10001	not available	The Bluetooth adapter is currently unavailable
10002	no device	The specified device was not found
10003	connection fail	The connection fails
10004	no service	The specified service was not found
10005	no characteristic	The specified characteristic value... Was not found
10006	no connection	The current connection has been disconnected
10007	property not support	The current eigenvalue does not support this operation
10008	system error	All other exceptions reported by the system
10009	system not support	Android System specific , The system version is lower than 4.3 I won't support it BLE

Be careful

• There is the possibility of reading failure when parallel calls are repeated .
• The information read by the interface needs to be in onBLECharacteristicValueChange Method to get .

Sample code

//  Only the callback here can get 
uni.onBLECharacteristicValueChange(function (characteristic) {
    
  console.log('characteristic value comed:', characteristic)
})
uni.readBLECharacteristicValue({
    
  //  there  deviceId  Need to have passed  createBLEConnection  Establish a link with the corresponding device 
  deviceId,
  //  there  serviceId  Need to be in  getBLEDeviceServices  Interface 
  serviceId,
  //  there  characteristicId  Need to be in  getBLEDeviceCharacteristics  Interface 
  characteristicId,
  success(res) {
    
    console.log('readBLECharacteristicValue:', res.errCode)
  }
})

4、 Listen for low-power Bluetooth connection status change events

uni.onBLEConnectionStateChange(CALLBACK)

Including developers actively connect or disconnect , Device lost , Abnormal disconnection of connection, etc

CALLBACK Returns the parameter

attribute	type	explain
deviceId	string	Bluetooth devices ID
connected	boolean	Whether it is connected

Sample code

uni.onBLEConnectionStateChange(function (res) {
    
  //  This method can be used in the callback to handle exceptions such as accidental disconnection of the connection 
  console.log(`device ${
      res.deviceId} state has changed, connected: ${
      res.connected}`)
})

5、 Monitor the eigenvalue change events of low-power Bluetooth devices

uni.onBLECharacteristicValueChange(CALLBACK)

You must first enable notifyBLECharacteristicValueChange The interface can receive the push from the device notification.

CALLBACK Returns the parameter

attribute	type	explain
deviceId	string	Bluetooth devices id
serviceId	string	The Bluetooth eigenvalue corresponds to the service uuid
characteristicId	string	Bluetooth eigenvalue uuid
value	ArrayBuffer	The latest value of the characteristic value

Sample code

// ArrayBuffer turn 16 Example progress string 
function ab2hex(buffer) {
    
  const hexArr = Array.prototype.map.call(
    new Uint8Array(buffer),
    function (bit) {
    
      return ('00' + bit.toString(16)).slice(-2)
    }
  )
  return hexArr.join('')
}
uni.onBLECharacteristicValueChange(function (res) {
    
  console.log(`characteristic ${
      res.characteristicId} has changed, now is ${
      res.value}`)
  console.log(ab2hex(res.value))
})

6、 Subscription characteristics

uni.notifyBLECharacteristicValueChange(OBJECT)

Enable low power Bluetooth device when the eigenvalue changes notify function , Subscription characteristics . Be careful ： The eigenvalue of the device must support notify perhaps indicate To successfully call . in addition , You must first enable notifyBLECharacteristicValueChange To listen to the device characteristicValueChange event

OBJECT Parameter description

attribute	type	The default value is	Required	explain
deviceId	string		yes	Bluetooth devices id
serviceId	string		yes	The Bluetooth eigenvalue corresponds to the service uuid
characteristicId	string		yes	Bluetooth eigenvalue uuid
state	boolean		yes	Is it enabled? notify
success	function		no	Interface calls the successful callback function
fail	function		no	Interface call failed callback function
complete	function		no	The callback function at the end of the interface call （ Successful call 、 Failure will be carried out ）

error

Error code	error message	explain
0	ok	normal
10000	not init	Bluetooth adapter not initialized
10001	not available	The Bluetooth adapter is currently unavailable
10002	no device	The specified device was not found
10003	connection fail	The connection fails
10004	no service	The specified service was not found
10005	no characteristic	The specified characteristic value... Was not found
10006	no connection	The current connection has been disconnected
10007	property not support	The current eigenvalue does not support this operation
10008	system error	All other exceptions reported by the system
10009	system not support	Android System specific , The system version is lower than 4.3 I won't support it BLE

Be careful

• After the subscription operation is successful, the device needs to actively update the characteristic value value, Will trigger uni.onBLECharacteristicValueChange Callback .
• On the Android platform , Calling notifyBLECharacteristicValueChange Call... Immediately after success writeBLECharacteristicValue Interface , On some models 10008 System error

Sample code

uni.notifyBLECharacteristicValueChange({
    
  state: true, //  Enable  notify  function 
  //  there  deviceId  Need to have passed  createBLEConnection  Establish a link with the corresponding device 
  deviceId,
  //  there  serviceId  Need to be in  getBLEDeviceServices  Interface 
  serviceId,
  //  there  characteristicId  Need to be in  getBLEDeviceCharacteristics  Interface 
  characteristicId,
  success(res) {
    
    console.log('notifyBLECharacteristicValueChange success', res.errMsg)
  }
})

7、 Get all services from Bluetooth devices (service)

uni.getBLEDeviceServices(OBJECT)

OBJECT Parameter description

attribute	type	The default value is	Required	explain
deviceId	string		yes	Bluetooth devices id
success	function		no	Interface calls the successful callback function
fail	function		no	Interface call failed callback function
complete	function		no	The callback function at the end of the interface call （ Successful call 、 Failure will be carried out ）

success Return parameter description ：

attribute	type	explain
services	Array	Equipment service list

res.services Structure

attribute	type	explain
uuid	string	Bluetooth device service uuid
isPrimary	boolean	Whether the service is the main service

error

Error code	error message	explain
0	ok	normal
10000	not init	Bluetooth adapter not initialized
10001	not available	The Bluetooth adapter is currently unavailable
10002	no device	The specified device was not found
10003	connection fail	The connection fails
10004	no service	The specified service was not found
10005	no characteristic	The specified characteristic value... Was not found
10006	no connection	The current connection has been disconnected
10007	property not support	The current eigenvalue does not support this operation
10008	system error	All other exceptions reported by the system
10009	system not support	Android System specific , The system version is lower than 4.3 I won't support it BLE

Sample code

uni.getBLEDeviceServices({
    
  //  there  deviceId  Need to have passed  createBLEConnection  Establish a link with the corresponding device 
  deviceId,
  success(res) {
    
    console.log('device services:', res.services)
  }
})

8、 Get the signal strength of Bluetooth device

uni.getBLEDeviceRSSI(OBJECT)

OBJECT Parameter description

attribute	type	The default value is	Required	explain
deviceId	string		yes	Bluetooth devices id
success	function		no	Interface calls the successful callback function
fail	function		no	Interface call failed callback function
complete	function		no	The callback function at the end of the interface call （ Successful call 、 Failure will be carried out ）

9、 Get all the eigenvalues in a service of a Bluetooth device (characteristic).

uni.getBLEDeviceCharacteristics(OBJECT)

OBJECT Parameter description

attribute	type	The default value is	Required	explain
deviceId	string		yes	Bluetooth devices id
serviceId	string		yes	Bluetooth service uuid, Need to use getBLEDeviceServices obtain
success	function		no	Interface calls the successful callback function
fail	function		no	Interface call failed callback function
complete	function		no	The callback function at the end of the interface call （ Successful call 、 Failure will be carried out ）

success Return parameter description ：

attribute	type	explain
characteristics	Array	Equipment service list

res.characteristics Structure

attribute	type	explain
uuid	string	Characteristic values of Bluetooth devices uuid
properties	Object	The operation types supported by this characteristic value

properties Structure

attribute	type	explain
read	boolean	Whether the characteristic value supports read operation
write	boolean	Whether the characteristic value supports write operation
notify	boolean	Whether the characteristic value supports notify operation
indicate	boolean	Whether the characteristic value supports indicate operation

error

Error code	error message	explain
0	ok	normal
10000	not init	Bluetooth adapter not initialized
10001	not available	The Bluetooth adapter is currently unavailable
10002	no device	The specified device was not found
10003	connection fail	The connection fails
10004	no service	The specified service was not found
10005	no characteristic	The specified characteristic value... Was not found
10006	no connection	The current connection has been disconnected
10007	property not support	The current eigenvalue does not support this operation
10008	system error	All other exceptions reported by the system
10009	system not support	Android System specific , The system version is lower than 4.3 I won't support it BLE

Sample code

uni.getBLEDeviceCharacteristics({
    
  //  there  deviceId  Need to have passed  createBLEConnection  Establish a link with the corresponding device 
  deviceId,
  //  there  serviceId  Need to be in  getBLEDeviceServices  Interface 
  serviceId,
  success(res) {
    
    console.log('device getBLEDeviceCharacteristics:', res.characteristics)
  }
})

10、 Connecting low power Bluetooth devices

uni.createBLEConnection(OBJECT)

if APP I have searched a Bluetooth device before , And successfully established the connection , You can directly enter the information obtained by previous search deviceId Try connecting the device directly , No search operation is required .

OBJECT Parameter description

attribute	type	The default value is	Required	explain
deviceId	string		yes	Used to distinguish between devices id
timeout	number		no	Timeout time , Company ms, If you don't fill in it, you won't timeout
success	function		no	Interface calls the successful callback function
fail	function		no	Interface call failed callback function
complete	function		no	The callback function at the end of the interface call （ Successful call 、 Failure will be carried out ）

error

Error code	error message	explain
0	ok	normal
10000	not init	Bluetooth adapter not initialized
10001	not available	The Bluetooth adapter is currently unavailable
10002	no device	The specified device was not found
10003	connection fail	The connection fails
10004	no service	The specified service was not found
10005	no characteristic	The specified characteristic value... Was not found
10006	no connection	The current connection has been disconnected
10007	property not support	The current eigenvalue does not support this operation
10008	system error	All other exceptions reported by the system
10009	system not support	Android System specific , The system version is lower than 4.3 I won't support it BLE

Be careful

• Please make sure to call in pairs as much as possible createBLEConnection and closeBLEConnection Interface . If Android calls many times createBLEConnection Create connection , It may cause the system to hold multiple connected instances of the same device , Results in a call to closeBLEConnection You can't really disconnect from the device .
• Bluetooth connection may be disconnected at any time , It is recommended to monitor uni.onBLEConnectionStateChange Callback events , When the Bluetooth device is disconnected, perform reconnection on demand
• If the interface of data read / write operation is called for an unconnected device or a disconnected device , Returns the 10006 error , Reconnection is recommended .

Sample code

uni.createBLEConnection({
    
  //  there  deviceId  Need to have passed  createBLEConnection  Establish a link with the corresponding device 
  deviceId,
  success(res) {
    
    console.log(res)
  }
})

11、 Disconnect from the low-power Bluetooth device .

uni.closeBLEConnection(OBJECT)

OBJECT Parameter description

attribute	type	The default value is	Required	explain
deviceId	string		yes	Used to distinguish between devices id
success	function		no	Interface calls the successful callback function
fail	function		no	Interface call failed callback function
complete	function		no	The callback function at the end of the interface call （ Successful call 、 Failure will be carried out ）

error

Error code	error message	explain
0	ok	normal
10000	not init	Bluetooth adapter not initialized
10001	not available	The Bluetooth adapter is currently unavailable
10002	no device	The specified device was not found
10003	connection fail	The connection fails
10004	no service	The specified service was not found
10005	no characteristic	The specified characteristic value... Was not found
10006	no connection	The current connection has been disconnected
10007	property not support	The current eigenvalue does not support this operation
10008	system error	All other exceptions reported by the system
10009	system not support	Android System specific , The system version is lower than 4.3 I won't support it BLE

Sample code

uni.closeBLEConnection({
    
  deviceId,
  success(res) {
    
    console.log(res)
  }
})

Implementation code ：

<script>
const LAST_CONNECTED_DEVICE = 'last_connected_device';
import PrinterJobs from '../../common/printer/printerjobs';
import printerUtil from '../../common/printer/printerutil';

function inArray(arr, key, val) {
    
	for (let i = 0; i < arr.length; i++) {
    
		if (arr[i][key] === val) {
    
			return i;
		}
	}
	return -1;
}

// ArrayBuffer turn 16 Example progress string 
function ab2hex(buffer) {
    
	const hexArr = Array.prototype.map.call(new Uint8Array(buffer), function(bit) {
    
		return ('00' + bit.toString(16)).slice(-2);
	});
	return hexArr.join(',');
}

function str2ab(str) {
    
	// Convert str to ArrayBuff and write to printer
	let buffer = new ArrayBuffer(str.length);
	let dataView = new DataView(buffer);
	for (let i = 0; i < str.length; i++) {
    
		dataView.setUint8(i, str.charAt(i).charCodeAt(0));
	}
	return buffer;
}

export default {
    
	data() {
    
		return {
    
			devices:[]  //  Devices searched 
		}
	};
},
onLoad(e) {
    
	this.openBluetoothAdapter()  //  Initialize Bluetooth module 
},
methods: {
    
	//  Initialize Bluetooth module 
		openBluetoothAdapter() {
    
			console.log(' Initialize Bluetooth module  openBluetoothAdapter');
			if (!uni.openBluetoothAdapter) {
    
				console.log(' Wechat version is too low ');
				uni.showModal({
    
					title: this.$t('wechat.w102'), //' Tips ',
					content: this.$t('wechat.w226') //' Current wechat version is too low , This feature is not available , Please upgrade to the latest wechat version and try again .'
				});
				return;
			}
			uni.openBluetoothAdapter({
    
				success: res => {
    
					console.log(' Successful initialization openBluetoothAdapter success', res);
					//  Search for Bluetooth nearby 
					this.startBluetoothDevicesDiscovery();
				},
				fail: res => {
    
					console.log(' initialization failed openBluetoothAdapter fail', res);
					if (res.errCode === 10001) {
    
						uni.showModal({
    
							title: this.$t('wechat.w227'), // error 
							content: this.$t('wechat.w228'), //' Bluetooth device not found ,  Please turn on Bluetooth and try again .',
							showCancel: false
						});
						//  Monitor Bluetooth adapter status change events 
						uni.onBluetoothAdapterStateChange(res => {
    
							console.log(' Monitor Bluetooth adapter status  onBluetoothAdapterStateChange', res);
							// available： Whether the Bluetooth adapter is available 
							if (res.available) {
    
								//  Cancel monitoring , otherwise stopBluetoothDevicesDiscovery It will continue to trigger onBluetoothAdapterStateChange,
								//  Cause to call again startBluetoothDevicesDiscovery
								// uni.onBluetoothAdapterStateChange(() => {});
								//  Start searching for Bluetooth peripherals nearby 
								this.startBluetoothDevicesDiscovery();
							}
						});
					}
				}
			});
		},
		//  Start searching for Bluetooth peripherals nearby 
		startBluetoothDevicesDiscovery() {
    
			if (this._discoveryStarted) {
    
				return;
			}
			this._discoveryStarted = true;
			uni.startBluetoothDevicesDiscovery({
    
				allowDuplicatesKey: false,
				interval: 0,
				success: res => {
    
					console.log(' Search for nearby Bluetooth peripherals  startBluetoothDevicesDiscovery success111', res);
					//  Listen for events that find new devices 
					this.onBluetoothDeviceFound();
				},
				fail: res => {
    
					console.log(' Search for nearby Bluetooth peripherals  startBluetoothDevicesDiscovery fail', res);
				}
			});
		},
		//  Listen for events that find new devices 
		onBluetoothDeviceFound() {
    
			console.log(' Enter the inquiry device ');
			uni.onBluetoothDeviceFound(res => {
    
				console.log(' Looking for equipment ', res.devices);
				res.devices.forEach(device => {
    
					if (!device.name && !device.localName) {
    
						return;
					}
					const foundDevices = this.devices;
					const idx = inArray(foundDevices, 'deviceId', device.deviceId);
					const data = {
    };
					if (idx === -1) {
    
						this.$set(this.devices, `${
      foundDevices.length}`, device);
					} else {
    
						this.$set(this.devices, `${
      idx}`, device);
					}
					// console.log(' The search results ',this.devices)
				});
			});
		},
		
		// this.devices Is a list of Bluetooth devices , Render to the page display, click to execute Bluetooth connection 
		//  Click on the link Bluetooth 
		createBLEConnection(e) {
    
			console.log(' Click Connect Bluetooth ', e);
			const deviceId = e.deviceId;
			const name = e.name;
			this._createBLEConnection(deviceId, name);
		},
		//  Connect Bluetooth devices 
		_createBLEConnection(deviceId, name) {
    
			this.$myToast(this.$t('wechat.w224'), 'loading'); // In connection device 
			//  Connecting low power Bluetooth devices 
			uni.createBLEConnection({
    
				deviceId, //  Used to distinguish between devices  id
				success: () => {
    
					console.log(' The call to connect the Bluetooth interface succeeded  createBLEConnection success', this.devices);
					this.devices.forEach((item, index) => {
    
						this.$set(this.devices[index], 'isShowConnect', false);
						if (item.deviceId === deviceId) {
    
							this.$set(this.devices[index], 'isShowConnect', true);
						}
					});
					this.$myToast(this.$t('wechat.w225'), 'success'); // Device connected successfully 
					this.connected = true;
					this.isConnected = false;
					this.name = name;
					this.deviceId = deviceId;
					//  Get all services from Bluetooth devices (service)
					this.getBLEDeviceServices(deviceId);
					//  Finally connect the device 
					uni.setStorage({
    
						key: LAST_CONNECTED_DEVICE,
						data: name + ':' + deviceId
					});
				},
				complete() {
    
					uni.hideLoading();
				},
				fail: res => {
    
					//  Call to connect Bluetooth interface failed 
					console.log(' Call to connect Bluetooth interface failed  createBLEConnection fail', res);
					uni.showModal({
    
						title: this.$t('wechat.w227'),
						content: ' Bluetooth connection failed ',
						showCancel: false
					});
				}
			});
			//  The Bluetooth device you need has been found , Stop searching for nearby Bluetooth peripherals 
			this.stopBluetoothDevicesDiscovery();
		},
		//  Get all services from Bluetooth devices (service)
		getBLEDeviceServices(deviceId) {
    
			uni.getBLEDeviceServices({
    
				deviceId,
				success: res => {
    
					console.log(' Get all services from Bluetooth devices  getBLEDeviceServices', res);
					for (let i = 0; i < res.services.length; i++) {
    
						if (res.services[i].isPrimary) {
    
							this.getBLEDeviceCharacteristics(deviceId, res.services[i].uuid);
							return;
						}
					}
				}
			});
		},
		stopBluetoothDevicesDiscovery() {
    
			uni.stopBluetoothDevicesDiscovery({
    
				complete: () => {
    
					// console.log('stopBluetoothDevicesDiscovery')
					this._discoveryStarted = false;
				}
			});
		},
		/*  Get all the eigenvalues in a service of a Bluetooth device (characteristic) characteristic: uuid: Characteristic values of Bluetooth devices  uuid properties: The operation types supported by this characteristic value  */
		getBLEDeviceCharacteristics(deviceId, serviceId) {
    
			uni.getBLEDeviceCharacteristics({
    
				//  there  deviceId  Need to have passed  createBLEConnection  Establish a link with the corresponding device 
				deviceId,
				//  there  serviceId( Bluetooth service  uuid)  Need to be in  getBLEDeviceServices  Interface 
				serviceId,
				success: res => {
    
					console.log(' Eigenvalue change  getBLEDeviceCharacteristics success', res.characteristics);
					//  There will be characteristic values that support write, The writing is successful but there is no response 
					//  You can only try one by one 
					// characteristics： Equipment service list 
					for (let i = 0; i < res.characteristics.length; i++) {
    
						const item = res.characteristics[i];
						// if (item.properties.read) {
    
						// uni.readBLECharacteristicValue({
    
						// deviceId,
						// serviceId,
						// characteristicId: item.uuid
						// })
						// }

						if (item.properties.write) {
    
							this.canWrite = true;
							this._deviceId = deviceId;
							this._serviceId = serviceId;
							this._characteristicId = item.uuid;
						}

						if (item.properties.notify || item.properties.indicate) {
    
							uni.notifyBLECharacteristicValueChange({
    
								deviceId,
								serviceId,
								characteristicId: item.uuid,
								state: true
							});
						}
					}
				},
				fail(res) {
    
					console.error(' Eigenvalue change  getBLEDeviceCharacteristics', res);
				}
			});
		},
		
		//  Click Print after Bluetooth connection is successful , Print data 
		//  Click Print ： Write data （ Print the content according to the needs of the project ）
		writeBLECharacteristicValue() {
    
			this.isLoading = true;
			setTimeout(() => {
    
				this.isDisabled = false;
				this.isLoading = false;
			}, 3000);
			let printerJobs = new PrinterJobs();
			const {
     channels, header, dataList } = this.printInfo;
			// console.log(' Channel data ', dataList)
			let title = '';
			header.forEach(item => {
    
				title = `${
      item.name} `;
			});
			//  Header information to print 
			printerJobs
				.setAlign('ct')
				.setSize(2, 2)
				.print(this.$t('wechat.w221')) //' Record reports '
				.setSize(0, 0)
				.print()
				.setAlign('lt')
				.setSize(1, 1)
				.print(`${
      this.$t('wechat.w51')}：${
      this.info.name}`) // Equipment name 
				.print(`${
      this.$t('wechat.w76')}：${
      this.info.modelName}`) // Model of equipment 
				.print(`${
      this.$t('wechat.w46')}：${
      this.info.deviceSerial}`) // Serial number 
				.print(`${
      this.$t('wechat.w100')}：${
      this.userInfo.relName}`) // user name 
				.print(`${
      this.$t('wechat.w101')}：${
      this.remark}`); // remarks 
			if (this.isEn) {
    
				channels.forEach(item => {
    
					printerJobs
						.print(`${
      item.name}(Max)：${
      item.max}${
      item.unitIcon}`)
						.print(`${
      this.$t('wechat.w148')}：${
      this.$timestampToTimeEn(item.maxDate)}`) // Time 
						.print(`${
      item.name}(Min)：${
      item.min}${
      item.unitIcon}`)
						.print(`${
      this.$t('wechat.w148')}：${
      this.$timestampToTimeEn(item.minDate)}`); // Time 
				});
			} else {
    
				channels.forEach(item => {
    
					printerJobs
						.print(`${
      item.name}(Max)：${
      item.max}${
      item.unitIcon}`)
						.print(`${
      this.$t('wechat.w148')}：${
      this.$timestampToTime2(item.maxDate)}`) // Time 
						.print(`${
      item.name}(Min)：${
      item.min}${
      item.unitIcon}`)
						.print(`${
      this.$t('wechat.w148')}：${
      this.$timestampToTime2(item.minDate)}`); // Time 
				});
			}

			printerJobs.print(printerUtil.fillLine()).setSize(1, 1);
			let titleStr = '';
			header.forEach((item, index) => {
    
				titleStr = titleStr + `${
      index === 0 ? '' : ' '}` + `${
      item.name}`;
			});
			printerJobs.print(printerUtil.inline(this.$t('wechat.w222'), `${
      titleStr}`)); // Recording time 

			//  Print '----------------'
			printerJobs.print(printerUtil.fillLine());
			//  What to print ：
			dataList.forEach(item => {
    
				let str = '';
				header.forEach((item2, index2) => {
    
					//  no 
					str = str + `${
      index2 === 0 ? '' : ' '}` + `${
      item[item2.columnName] ? item[item2.columnName].toFixed(2) : this.$t('wechat.w71empty')}`;
				});

				if (this.isEn) {
    
					printerJobs.print(printerUtil.inline(`${
      this.$timestampToTimeEn2(item.dataTime)}`, `${
      str}`));
				} else {
    
					printerJobs.print(printerUtil.inline(`${
      this.$timestampToTime3(item.dataTime)}`, `${
      str}`));
				}
				// console.log(`${item.dataTime}`, str);
			});
			//  ending 
			printerJobs
				.println()
				.print(`${
      this.$t('wechat.w223')}：`) //' Signature 
				.println()
				.println();

			let buffer = printerJobs.buffer();
			// console.log('ArrayBuffer', 'length: ' + buffer.byteLength, ' hex: ' + ab2hex(buffer));
			// 1. There is a possibility of write failure when parallel calls are repeated 
			// 2. It is recommended that no more than... Be written each time 20 byte 
			//  Subcontracting , Delay call 
			const maxChunk = 20;
			const delay = 40;
			for (let i = 0, j = 0, length = buffer.byteLength; i < length; i += maxChunk, j++) {
    
				let subPackage = buffer.slice(i, i + maxChunk <= length ? i + maxChunk : length);
				// subPackage： Parameters 
				setTimeout(this._writeBLECharacteristicValue, j * delay, subPackage);
			}
		},
		//  Write binary data to the characteristic value of low-power Bluetooth device . Be careful ： The eigenvalue of the device must support  write  To successfully call .
		_writeBLECharacteristicValue(buffer) {
    
			uni.writeBLECharacteristicValue({
    
				deviceId: this._deviceId, //  Bluetooth devices  id
				serviceId: this._serviceId, //  The Bluetooth eigenvalue corresponds to the service  uuid
				characteristicId: this._characteristicId, //  Bluetooth eigenvalue  uuid
				value: buffer, //  The binary value corresponding to the characteristic value of the Bluetooth device 
				success(res) {
    
					console.log('writeBLECharacteristicValue success', res);
				},
				fail(res) {
    
					console.log('writeBLECharacteristicValue fail', res);
				}
			});
		},
		
		



}

Printing effect ：

Other documents ：

1. printerutil.js

//  Printer paper width 58mm, Width of page 384, The character width is 1, Each row can hold at most 32 Characters 
const PAGE_WIDTH = 384;
const MAX_CHAR_COUNT_EACH_LINE = 32;

/** * @param str * @returns {boolean} str Is it all Chinese  */
function isChinese(str) {
    
  return /^[\u4e00-\u9fa5]$/.test(str);
}

/** *  Return string width (1 Chinese =2 English characters ) * @param str * @returns {number} */
function getStringWidth(str) {
    
  let width = 0;
  for (let i = 0, len = str.length; i < len; i++) {
    
    width += isChinese(str.charAt(i)) ? 2 : 1;
  }
  return width;
}

/** *  Output on the same line str1, str2,str1 be at the left side , str2 be at the right  * @param {string} str1  Content 1 * @param {string} str2  Content 2 * @param {number} fontWidth  Character width  1/2 * @param {string} fillWith str1 str2 Fill characters between  * */
function inline(str1, str2, fillWith = ' ', fontWidth = 1) {
    
  const lineWidth = MAX_CHAR_COUNT_EACH_LINE / fontWidth;
  //  The number of characters to fill 
  let fillCount = lineWidth - (getStringWidth(str1) + getStringWidth(str2)) % lineWidth;
  let fillStr = new Array(fillCount).fill(fillWith.charAt(0)).join('');
  return str1 + fillStr + str2;
}

/** *  Fill a whole line with characters  * @param {string} fillWith  Fill character  * @param {number} fontWidth  Character width  1/2 */
function fillLine(fillWith = '-', fontWidth = 1) {
    
  const lineWidth = MAX_CHAR_COUNT_EACH_LINE / fontWidth;
  return new Array(lineWidth).fill(fillWith.charAt(0)).join('');
}

/** *  The text content is centered , Fill left and right with characters  * @param {string} str  Written content  * @param {number} fontWidth  Character width  1/2 * @param {string} fillWith str1 str2 Fill characters between  */
function fillAround(str, fillWith = '-', fontWidth = 1) {
    
  const lineWidth = MAX_CHAR_COUNT_EACH_LINE / fontWidth;
  let strWidth = getStringWidth(str);
  //  The content has exceeded one line , There is no need to fill 
  if (strWidth >= lineWidth) {
    
    return str;
  }
  //  The number of characters to fill 
  let fillCount = lineWidth - strWidth;
  //  The number of characters filled on the left 
  let leftCount = Math.round(fillCount / 2);
  //  Padding characters on both sides , It needs to be considered that the left side needs to be filled , The right side does not need to be filled 
  let fillStr = new Array(leftCount).fill(fillWith.charAt(0)).join('');
  return fillStr + str + fillStr.substr(0, fillCount - leftCount);
}

module.exports = {
    
  inline: inline,
  fillLine: fillLine,
  fillAround: fillAround,
};

2. printerjobs.js

const commands = require('./commands.js');
const TextEncoder = require('../text-encoding/index').TextEncoder;

const printerJobs = function () {
    
  this._queue = Array.from(commands.HARDWARE.HW_INIT);
  this._encoder = new TextEncoder("gb2312", {
    NONSTANDARD_allowLegacyEncoding: true});
  this._enqueue = function (cmd) {
    
    this._queue.push.apply(this._queue, cmd);
  }
};

/** *  Add print content  * @param {string} content  Written content  */
printerJobs.prototype.text = function (content) {
    
  if (content) {
    
    let uint8Array = this._encoder.encode(content);
    let encoded = Array.from(uint8Array);
    this._enqueue(encoded);
  }
  return this;
};

/** *  Print text  * @param {string} content  Written content  */
printerJobs.prototype.print = function (content) {
    
  this.text(content);
  this._enqueue(commands.LF);
  return this;
};

/** *  Print text and wrap  * @param {string} content  Written content  */
printerJobs.prototype.println = function (content = '') {
    
  return this.print(content + commands.EOL);
};

/** *  Set alignment  * @param {string} align  Alignment mode  LT/CT/RT */
printerJobs.prototype.setAlign = function (align) {
    
  this._enqueue(commands.TEXT_FORMAT['TXT_ALIGN_' + align.toUpperCase()]);
  return this;
};

/** *  Set the font  * @param {string} family A/B/C */
printerJobs.prototype.setFont = function (family) {
    
  this._enqueue(commands.TEXT_FORMAT['TXT_FONT_' + family.toUpperCase()]);
  return this;
};

/** *  Set the font size  * @param {number} width  Font width  1~2 * @param {number} height  Font height  1~2 */
printerJobs.prototype.setSize = function (width, height) {
    
  if (2 >= width && 2 >= height) {
    
    this._enqueue(commands.TEXT_FORMAT.TXT_NORMAL);
    if (2 === width && 2 === height) {
    
      this._enqueue(commands.TEXT_FORMAT.TXT_4SQUARE);
    } else if (1 === width && 2 === height) {
    
      this._enqueue(commands.TEXT_FORMAT.TXT_2HEIGHT);
    } else if (2 === width && 1 === height) {
    
      this._enqueue(commands.TEXT_FORMAT.TXT_2WIDTH);
    }
  }
  return this;
};

/** *  Set whether the font is bold  * @param {boolean} bold */
printerJobs.prototype.setBold = function (bold) {
    
  if (typeof bold !== 'boolean') {
    
    bold = true;
  }
  this._enqueue(bold ? commands.TEXT_FORMAT.TXT_BOLD_ON : commands.TEXT_FORMAT.TXT_BOLD_OFF);
  return this;
};

/** *  Set whether underline is turned on  * @param {boolean} underline */
printerJobs.prototype.setUnderline = function (underline) {
    
  if (typeof underline !== 'boolean') {
    
    underline = true;
  }
  this._enqueue(underline ? commands.TEXT_FORMAT.TXT_UNDERL_ON : commands.TEXT_FORMAT.TXT_UNDERL_OFF);
  return this;
};

/** *  Set the line spacing to  n  Click line , The default line spacing is  30  spot  * @param {number} n 0≤n≤255 */
printerJobs.prototype.setLineSpacing = function (n) {
    
  if (n === undefined || n === null) {
    
    this._enqueue(commands.LINE_SPACING.LS_DEFAULT);
  } else {
    
    this._enqueue(commands.LINE_SPACING.LS_SET);
    this._enqueue([n]);
  }
  return this;
};

/** *  Print blank lines  * @param {number} n */
printerJobs.prototype.lineFeed = function (n = 1) {
    
  return this.print(new Array(n).fill(commands.EOL).join(''));
};

/** *  Set font color , Printer support is required  * @param {number} color - 0  Default color black  1  Red  */
printerJobs.prototype.setColor = function (color) {
    
  this._enqueue(commands.COLOR[color === 1 ? 1 : 0]);
  return this;
};

/** * https://support.loyverse.com/hardware/printers/use-the-beeper-in-a-escpos-printers *  Beep alarm , Printer support is required  * @param {number} n  Number of beeps ,1-9 * @param {number} t  Buzzer length ,1-9 */
printerJobs.prototype.beep = function (n, t) {
    
  this._enqueue(commands.BEEP);
  this._enqueue([n, t]);
  return this;
};

/** *  Clear task  */
printerJobs.prototype.clear = function () {
    
  this._queue = Array.from(commands.HARDWARE.HW_INIT);
  return this;
};

/** *  return ArrayBuffer */
printerJobs.prototype.buffer = function () {
    
  return new Uint8Array(this._queue).buffer;
};

module.exports = printerJobs;

3. commands.js

/** *  Modified from https://github.com/song940/node-escpos/blob/master/commands.js * ESC/POS _ (Constants) */
var _ = {
    
  LF: [0x0a],
  FS: [0x1c],
  FF: [0x0c],
  GS: [0x1d],
  DLE: [0x10],
  EOT: [0x04],
  NUL: [0x00],
  ESC: [0x1b],
  EOL: '\n',
};

/** * [FEED_CONTROL_SEQUENCES Feed control sequences] * @type {Object} */
_.FEED_CONTROL_SEQUENCES = {
    
  CTL_LF: [0x0a],   // Print and line feed  Print line breaks 
  CTL_GLF: [0x4a, 0x00],   // Print and feed paper (without spaces between lines)  Printing and paper feeding ( No space between lines )
  CTL_FF: [0x0c],   // Form feed  Change the page 
  CTL_CR: [0x0d],   // Carriage return
  CTL_HT: [0x09],   // Horizontal tab  enter 
  CTL_VT: [0x0b],   // Vertical tab  Vertical tabs 
};

_.CHARACTER_SPACING = {
    
  CS_DEFAULT: [0x1b, 0x20, 0x00],
  CS_SET: [0x1b, 0x20]
};

_.LINE_SPACING = {
    
  LS_DEFAULT: [0x1b, 0x32],
  LS_SET: [0x1b, 0x33]
};

/** * [HARDWARE Printer hardware] * @type {Object} */
_.HARDWARE = {
    
  HW_INIT: [0x1b, 0x40], // Clear data in buffer and reset modes
  HW_SELECT: [0x1b, 0x3d, 0x01], // Printer select
  HW_RESET: [0x1b, 0x3f, 0x0a, 0x00], // Reset printer hardware
};

/** * [CASH_DRAWER Cash Drawer] * @type {Object} */
_.CASH_DRAWER = {
    
  CD_KICK_2: [0x1b, 0x70, 0x00], // Sends a pulse to pin 2 []
  CD_KICK_5: [0x1b, 0x70, 0x01], // Sends a pulse to pin 5 []
};

/** * [MARGINS Margins sizes] * @type {Object} */
_.MARGINS = {
    
  BOTTOM: [0x1b, 0x4f], // Fix bottom size
  LEFT: [0x1b, 0x6c], // Fix left size
  RIGHT: [0x1b, 0x51], // Fix right size
};

/** * [PAPER Paper] * @type {Object} */
_.PAPER = {
    
  PAPER_FULL_CUT: [0x1d, 0x56, 0x00], // Full cut paper
  PAPER_PART_CUT: [0x1d, 0x56, 0x01], // Partial cut paper
  PAPER_CUT_A: [0x1d, 0x56, 0x41], // Partial cut paper
  PAPER_CUT_B: [0x1d, 0x56, 0x42], // Partial cut paper
};

/** * [TEXT_FORMAT Text format] * @type {Object} */
_.TEXT_FORMAT = {
    
  TXT_NORMAL: [0x1b, 0x21, 0x00], // Normal text
  TXT_2HEIGHT: [0x1b, 0x21, 0x10], // Double height text  Double height text 
  TXT_2WIDTH: [0x1b, 0x21, 0x20], // Double width text  Double width text 
  TXT_4SQUARE: [0x1b, 0x21, 0x30], // Double width & height text  Double width and height text 

  TXT_UNDERL_OFF: [0x1b, 0x2d, 0x00], // Underline font OFF 
  TXT_UNDERL_ON: [0x1b, 0x2d, 0x01], // Underline font 1-dot ON
  TXT_UNDERL2_ON: [0x1b, 0x2d, 0x02], // Underline font 2-dot ON
  TXT_BOLD_OFF: [0x1b, 0x45, 0x00], // Bold font OFF
  TXT_BOLD_ON: [0x1b, 0x45, 0x01], // Bold font ON
  TXT_ITALIC_OFF: [0x1b, 0x35], // Italic font ON
  TXT_ITALIC_ON: [0x1b, 0x34], // Italic font ON

  TXT_FONT_A: [0x1b, 0x4d, 0x00], // Font type A
  TXT_FONT_B: [0x1b, 0x4d, 0x01], // Font type B
  TXT_FONT_C: [0x1b, 0x4d, 0x02], // Font type C

  TXT_ALIGN_LT: [0x1b, 0x61, 0x00], // Left justification
  TXT_ALIGN_CT: [0x1b, 0x61, 0x01], // Centering
  TXT_ALIGN_RT: [0x1b, 0x61, 0x02], // Right justification
};

/** * [BARCODE_FORMAT Barcode format] * @type {Object} */
_.BARCODE_FORMAT = {
    
  BARCODE_TXT_OFF: [0x1d, 0x48, 0x00], // HRI barcode chars OFF
  BARCODE_TXT_ABV: [0x1d, 0x48, 0x01], // HRI barcode chars above
  BARCODE_TXT_BLW: [0x1d, 0x48, 0x02], // HRI barcode chars below
  BARCODE_TXT_BTH: [0x1d, 0x48, 0x03], // HRI barcode chars both above and below

  BARCODE_FONT_A: [0x1d, 0x66, 0x00], // Font type A for HRI barcode chars
  BARCODE_FONT_B: [0x1d, 0x66, 0x01], // Font type B for HRI barcode chars

  BARCODE_HEIGHT: function (height) {
     // Barcode Height [1-255]
    return [0x1d, 0x68, height];
  },
  BARCODE_WIDTH: function (width) {
       // Barcode Width [2-6]
    return [0x1d, 0x77, width];
  },
  BARCODE_HEIGHT_DEFAULT: [0x1d, 0x68, 0x64], // Barcode height default:100
  BARCODE_WIDTH_DEFAULT: [0x1d, 0x77, 0x01], // Barcode width default:1

  BARCODE_UPC_A: [0x1d, 0x6b, 0x00], // Barcode type UPC-A
  BARCODE_UPC_E: [0x1d, 0x6b, 0x01], // Barcode type UPC-E
  BARCODE_EAN13: [0x1d, 0x6b, 0x02], // Barcode type EAN13
  BARCODE_EAN8: [0x1d, 0x6b, 0x03], // Barcode type EAN8
  BARCODE_CODE39: [0x1d, 0x6b, 0x04], // Barcode type CODE39
  BARCODE_ITF: [0x1d, 0x6b, 0x05], // Barcode type ITF
  BARCODE_NW7: [0x1d, 0x6b, 0x06], // Barcode type NW7
  BARCODE_CODE93: [0x1d, 0x6b, 0x48], // Barcode type CODE93
  BARCODE_CODE128: [0x1d, 0x6b, 0x49], // Barcode type CODE128
};

/** * [IMAGE_FORMAT Image format] * @type {Object} */
_.IMAGE_FORMAT = {
    
  S_RASTER_N: [0x1d, 0x76, 0x30, 0x00], // Set raster image normal size
  S_RASTER_2W: [0x1d, 0x76, 0x30, 0x01], // Set raster image double width
  S_RASTER_2H: [0x1d, 0x76, 0x30, 0x02], // Set raster image double height
  S_RASTER_Q: [0x1d, 0x76, 0x30, 0x03], // Set raster image quadruple
};

/** * [BITMAP_FORMAT description] * @type {Object} */
_.BITMAP_FORMAT = {
    
  BITMAP_S8: [0x1b, 0x2a, 0x00],
  BITMAP_D8: [0x1b, 0x2a, 0x01],
  BITMAP_S24: [0x1b, 0x2a, 0x20],
  BITMAP_D24: [0x1b, 0x2a, 0x21]
};

/** * [GSV0_FORMAT description] * @type {Object} */
_.GSV0_FORMAT = {
    
  GSV0_NORMAL: [0x1d, 0x76, 0x30, 0x00],
  GSV0_DW: [0x1d, 0x76, 0x30, 0x01],
  GSV0_DH: [0x1d, 0x76, 0x30, 0x02],
  GSV0_DWDH: [0x1d, 0x76, 0x30, 0x03]
};

/** * [BEEP description] * @type {string} */
_.BEEP = [0x1b, 0x42]; // Printer Buzzer pre hex

/** * [COLOR description] * @type {Object} */

_.COLOR = {
    
  0: [0x1b, 0x72, 0x00], // black
  1: [0x1b, 0x72, 0x01] // red
};

/** * [exports description] * @type {[type]} */
module.exports = _;

notes ：
1、 The connected Bluetooth must be low-power Bluetooth , Classic Bluetooth cannot be searched （ Because you can't execute uni.onBluetoothDeviceFound）
2、 Some mobile phones need to turn on the location to search for Bluetooth （ Start positioning to execute uni.onBluetoothDeviceFound）