Nrf52832 custom services and features

The experiment purpose ： Customize Service Private service and transmission of temperature and humidity sensor data . This experiment is based on SDK17.02 in ble_app_uart Change the sample code .
One 、 background
1.1GAP initialization ：
   Mainly complete three tasks ：
a.GAP Initialize safe mode configuration , Security mode refers to whether authentication is required when connecting .
b. Bluetooth device name settings , That is, set the name of Bluetooth broadcast , Note that the length of the name is limited , It's best not to exceed eighteen bytes
c. Connection parameter settings , Connection parameter settings , It's mainly about setting up ： Minimum connection interval 、 Maximum connection interval 、 Latency cycle of slave equipment 、 Connection timeout . These values represent the expected parameters of the peripheral for the connection .
1.2GATT initialization
GATT It is called the general attribute specification （Generic Attribute profile,GATT）,GATT The layer is where the real data is transmitted layer . It includes a data transmission and storage framework and its basic operation . Most of its custom functions are in .C Written , In the main function, you only need to initialize and configure the relationship between functions .
GATT Used ATT（Attribute Protocol） agreement ,ATT The agreement put Service,Characteristic The corresponding data is saved in a lookup table , Lookup table usage 16bit ID As an index of each item .GATT The defined multi-layer data structure can be summarized as service （Service） It can contain more than one features （Characteristic）, Each feature contains attribute （Properties） and value （Value）, It can also contain multiple describe （Descriptor）.

Two 、ble_lbs.c function
battery_level Is the of analog electricity value
2.1 Host client event handling
ble_lbs.h Observer mode NRF_SDH_BLE_OBSERVER—>>>ble_lbs_on_ble_evt—>>>lbs_c_evt_handler()

case BLE_GATTS_EVT_WRITE: //LED When a feature is written to data , Produced GATT Write events , Will call on_write function .
lbs_c_evt_handler(p_lbs, p_ble_evt); 

ble_lbs_on_ble_evt—>>>lbs_c_evt_handler()

p_lbs->led_write_handler(p_ble_evt->evt.gap_evt.conn_handle, p_lbs, p_evt_write->data[0]);
ble_srv_is_notification_enabled(p_evt_write->data)

2.2 Host client initialization ble_lbs_init()

// Initialize service structure
p_lbs->evt_handler               = p_lbs_init->evt_handler;
p_lbs->is_notification_supported = p_lbs_init->support_notification;
p_lbs->battery_level_last        = INVALID_BATTERY_LEVEL;
// Add service
BLE_UUID_BLE_ASSIGN(ble_uuid, BLE_UUID_BATTERY_SERVICE);
// Add battery level characteristic
err_code = battery_level_char_add(p_lbs, p_lbs_init);

Feature add function battery_level_char_add()

memset(&cccd_md, 0, sizeof(cccd_md));
BLE_GAP_CONN_SEC_MODE_SET_OPEN(&cccd_md.read_perm);

memset(&char_md, 0, sizeof(char_md));
BLE_UUID_BLE_ASSIGN(ble_uuid, BLE_UUID_BATTERY_LEVEL_CHAR);

memset(&attr_md, 0, sizeof(attr_md));
initial_battery_level = p_bas_init->initial_batt_level;

memset(&attr_char_value, 0, sizeof(attr_char_value));
err_code = sd_ble_gatts_characteristic_add(p_bas->service_handle, &char_md,
                                           &attr_char_value,
                                           &p_bas->battery_level_handles);

2.3 Host client temperature data processing function
main.c Timer call battery_level_update()：

memset(&gatts_value, 0, sizeof(gatts_value));
err_code = sd_ble_gatts_value_set(BLE_CONN_HANDLE_INVALID,
                                  p_bas->battery_level_handles.value_handle,
                                  &gatts_value);
err_code = battery_notification_send(&hvx_params, conn_handles.conn_handles[i]);                                                                         

battery_level_update()—>>>battery_notification_send()

err_code = sd_ble_gatts_hvx(conn_handle, p_hvx_params);

3、 ... and .main.c function
3.1. Macro definition

APP_TIMER_DEF(m_battery_timer_id); 
BLE_LBS_mpu6050_DEF(m_mpu6050);// Observer mode 
static ble_lbs_t m_mpu6050;
ble_bas_battery_level_update(&m_mpu6050, TIME_TEMP, BLE_CONN_HANDLE_ALL);

3.2.services_init
Mainly initialization ble_lbs.c Inside ble_lbs_init

ble_lbs_init_t bas_init_obj;    
memset(&bas_init_obj, 0, sizeof(bas_init_obj));
err_code = ble_lbs_init(&m_mpu6050, &bas_init_obj);

3.3. Timer
Callback function measure_timer_handler

TIME_TEMP Is an analog value 
ble_bas_battery_level_update(&m_mpu6050, TIME_TEMP, BLE_CONN_HANDLE_ALL);