Wireless communication module fixed-point transmission - point to multipoint specific transmission application

1.    Development background of wireless module communication transmission

    In the wireless communication transmission application of the Internet of things , There are often multiple in the same environment Wireless communication module In the use of , Due to the characteristics of RF itself , It is easy to cause interference during the mutual transmission of wireless modules . Interference is caused by the simultaneous transmission of multiple pairs of wireless modules in the same environment . When multiple wireless modules are in the same communication frequency band , When a module is sending , All modules in the same frequency band can receive , When multiple messages are sent at the same time , Will cause interference , In this case, it will be impossible to receive . however , Some applications require modules in different frequency bands to communicate , Or you need to implement custom networking applications , It is necessary to avoid such interference .

    In order to avoid the occurrence of such interference and the feasibility of the above applications , Chengdu yibaite Electronic Technology Co., Ltd. has launched a transmission mode -- Fixed point transmission .

2.    Introduction to fixed-point transmission

The fixed-point transmission mode promoted by Chengdu ebat Electronic Technology Co., Ltd. can realize cross channel transmission and cross address transmission . For the traditional serial port module , The communication frequency can be set generally , But the communication channel must be the same . For the wireless serial port module of Chengdu yibaite Electronic Technology Co., Ltd , Maximum channel support 256 individual , Address support range 0 -- 65535, Plus the fixed-point transmission function , In the same environment, enough pairs of wireless modules are allowed to be used in pairs without mutual interference .

Fixed point transmission refers to any channel 、 The wireless serial port module with any address can send data to any channel 、 Another wireless module at any address . The specific address to be transmitted 、 Module of the channel , It is determined by the content of data sent by the sending module .

For example, by A Send to at a fixed point D, If A The module address is 0xaaaa,A The channel of is 0xaa;B The module address is 0xbbbb, The channel is 0xbb;C The module address is 0xcccc, The channel is 0xcc;D The module address is 0xdddd, The channel is 0xdd;E The module address is 0xeeee, The channel is 0xee. that A Send to D The data format of is ：dd dd dd + The data content . Data is sent in 16 Base send .

3.    Fixed point transmission mode — Point to multipoint applications

1.   Point to multipoint short distance transmission

Point to multipoint short-range transmission is relatively simple , It's easy to understand . Here's the picture , In this environment, there are ABCD Four receiving devices , The sending device needs to send data to ABCD Any receiving device , Only one device can receive each transmission , Then the sending device only needs to add the address of the target device to the front of the sending data content , Target device channel , After sending it out , Can only be received by the target device , Other devices cannot receive any data .

If the sending device needs to send data to A Receiving equipment , Then the format of sending data only needs to be added before sending data A Address and channel of receiving equipment , If A The device address is 0x0001, The channel is 0x0001, If B The device address is 0x0002, The channel is 0x0002, If C The device address is 0x0003, The channel is 0x0003, If D The device address is 0x0004, The channel is 0x0004. At this time, the sending device sends it to A when , The data format is ：00 01 01 11 22 33 44, among 00 01 For address ,01 Is channel ,11 2233 44 Bit sent content . It's just A The device can receive data 1122 33 44, Other devices receive data . Similarly, if the sending device needs to send data 11 22 33 44 to D Receiving equipment , Then the format of the sent data is ：00 04 04 11 22 33 44. This transmission mode can realize point to multipoint transmission application , The transmission initiator is usually initiated by the sending host , But not necessarily , It can also be adjusted according to the actual application situation of users , Choose a reasonable transmission mode , Realize point to multipoint custom networking application .

2.   Point to multipoint long distance relay transmission

Point to point long-distance relay transmission data transmission is relatively complicated , That is, the protocol header needs to add two or more data headers sent at a fixed point , This transmission mode is suitable for long-distance transmission , However, the data volume shall not exceed the length of a packet of data .

for example ： The address of the wireless serial port module of the relay is 0x0001, The channel is 0x01; The address of the module at the target receiving end is 0x0010, The channel is 0x10, Then the data format sent by the sender should be ：

00 0101 00 10 10 +  data

among , First three bytes  00 01 01 Address and channel for relay ,00 10 10 Is the address and channel of the target wireless module . After sending in this way , Only data is received by the target , The protocol header channel address has been filtered out .

As shown in the figure below , This scheme is suitable for long-distance relay , And support one to many , When a line fails to communicate for a long time , Can change a line to communicate . This mesh point to multipoint function is much more complex , But it is more flexible than single point to single point .

    This relay mode saves the controller control of the relay section , The module's RX、TX Pin is short circuited , Relay can be realized , The controller is saved in cost , And easy to install . However, the number of bytes sent by this relay method is limited by the packet length , The number of bytes sent at a time cannot exceed the packet length .

4.   review

The point to multipoint application is a slightly more complex wireless communication application of the Internet of things , As long as you understand the point-to-point application , That point to multipoint is also very convenient , These applications are based on the wireless communication module of wireless serial port , So I can get started quickly , Customers do not need to consider RF drive , You can send and receive data directly according to the user manual , more Wireless serial port module Please pay attention to Chengdu yibaite Electronic Technology Co., Ltd .