5. BLE Client And Server Interconnection

This demo is based on bl702 to demonstrate the connection and data sending and receiving of ble server and ble client.

5.1. Prepare

  • Two bl702 boards or one bl702 board + mobile app

5.2. Software Implementation

5.2.1. BLE client software Implementation

  • For the software code, see examples/ble/ble_central

 1static struct bt_conn_cb ble_tp_conn_callbacks = {
 2 .connected = ble_tp_connected,
 3 .disconnected = ble_tp_disconnected,
 4}
 5
 6void ble_tp_init()
 7{
 8    if( !isRegister )
 9    {
10        isRegister = 1;
11        bt_conn_cb_register(&ble_tp_conn_callbacks);
12    }
13}

  • In the bt_conn_cb_register function, register the callback function for successful connection and disconnection

  • In the ble_start_scan function, the device will start scanning

  • In the device_found function, the device uploads the scanned Bluetooth device, the code uses adv_name to find the Bluetooth device that needs to be connected, and initiate the connection

 1static void ble_write_data_task(void *pvParameters)
 2{
 3    int error;
 4    uint8_t buf[20] = {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19};
 5    while(1)
 6   {
 7        k_sem_take(&write_data_poll_sem, K_FOREVER);
 8        BT_WARN("ble_write_data\r\n");
 9        // Send data to server
10        error =  bt_gatt_write_without_response(ble_tp_conn,char_hdl.tp_wr_hdl,buf,20,0);
11        BT_WARN("Write Complete (err %d)\r\n", error);
12   }
13}

  • After the connection is successful, in the ble_write_data_task function, the client sends the data in buf to the server

1static u8_t notify_func(struct bt_conn *conn,struct bt_gatt_subscribe_params *params,const void *data, u16_t length);

  • After the connection is successful, in the notify_func function, the client receives the data from the server, data is the data content, length is the data length

5.2.2. BLE server software implementation

  • See examples/ble/ble_peripheral for the software code

 1int ble_start_adv(void)
 2{
 3    struct bt_le_adv_param adv_param = {
 4        //options:3, connectable undirected, adv one time
 5        .options = 3, \
 6        .interval_min = BT_GAP_ADV_FAST_INT_MIN_3, \
 7        .interval_max = BT_GAP_ADV_FAST_INT_MAX_3, \
 8    };
 9
10
11    char *adv_name = "BL_TEST_01"; // This name must be the same as adv_name in ble_central
12    uint8_t data[1] = {(BT_LE_AD_LIMITED | BT_LE_AD_NO_BREDR)};
13    uint8_t data_uuid[2] = {0x12, 0x18};//0x1812
14    uint8_t data_appearance[2] = {0x80, 0x01};//0x0180
15    uint8_t data_manu[4] = {0x71, 0x01, 0x04, 0x13};
16    struct bt_data adv_data[] = {
17            BT_DATA(BT_DATA_FLAGS, data, 1),
18            BT_DATA(BT_DATA_UUID16_ALL, data_uuid, sizeof(data_uuid)),
19            BT_DATA(BT_DATA_GAP_APPEARANCE, data_appearance, sizeof(data_appearance)),
20            BT_DATA(BT_DATA_NAME_COMPLETE, adv_name, strlen(adv_name)),
21            BT_DATA(BT_DATA_MANUFACTURER_DATA, data_manu, sizeof(data_manu))
22        };
23
24
25    return bt_le_adv_start(&adv_param, adv_data, ARRAY_SIZE(adv_data), NULL, 0);
26}

  • In the ble_start_adv function, adv_name sets the name of the broadcast device, and the device starts to broadcast

1static int ble_tp_recv_wr(struct bt_conn *conn, const struct bt_gatt_attr *attr,const void *buf, u16_t len, u16_t offset, u8_t flags);

-After the connection is successful, in ble_tp_recv_wr, the server receives the data from the client, buf is the data content, len is the data length

 1static void ble_tp_notify_task(void *pvParameters)
 2{
 3    int err = -1;
 4    char data[244] = {0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09};
 5    k_sem_give(&notify_poll_sem);
 6    while(1)
 7    {
 8        k_sem_take(&notify_poll_sem, K_FOREVER);
 9        //send data to client
10        err = bt_gatt_notify(ble_tp_conn, get_attr(BT_CHAR_BLE_TP_NOT_ATTR_VAL_INDEX), data, (tx_mtu_size - 3));
11        BT_WARN("ble tp send notify : %d\n", err);
12
13    }
14}

  • After the connection is successful, in the ble_tp_notify_task function, the server sends the data in data to the client.

5.3. Compile and program

  • CDK tool compilation

    Not currently supported

  • Command compilation

1 $ cd <sdk_path>/bl_mcu_sdk
2 $ make BOARD=bl706_iot APP=ble_peripheral SUPPORT_FREERTOS=y SUPPORT_FLOAT=y SUPPORT_BLE=y

1 $ cd <sdk_path>/bl_mcu_sdk
2 $ make BOARD=bl706_iot APP=ble_central SUPPORT_FREERTOS=y SUPPORT_FLOAT=y SUPPORT_BLE=y

5.4. Experimental phenomena

  • Two bl702 connections

  • Mobile phone connect bl702

  • The connection is successful, as shown in the figure below

  • Steps to send and receive data

    • Click 1 Unknow Service to display specific service properties

    • Click 2 to turn on Notification, allowing the server to send data to the client

    • Click 3 where the client sends data to the server, fill in the data you want to send, and click the SEND button