bt_gatt_client_subscribe()

Description

This function subscribe to value notification using the Client Characteristic Configuration handle. If notification received subscribe value callback is called to return notified value.

Syntax

bt_gatt_client_subscribe(connection_id, chrc_value_handle, ccc_handle, subscription_type);

Parameters

Variable	Input

Variable	Input
`connection_id`	Connection id which was described in `bt_gatt_client_connect` function. Could be either 0 or 1.
`chrc_value_handle`	Characteristic value handle to subscribe to.
`ccc_handle`	Handle of client characteristic configuration descriptor. In almost all cases ccc handle is going to be: `chrc_value_handle + 1`.
`subscription_type`	Can be either: BT_GATT_CCC_NOTIFY - Unacknowledged (no response needed from client). BT_GATT_CCC_INDICATE - Acknowledged (client confirms receipt for server).

Returns

Return value	Return explanation
SCRIPT_OPERATION_SUCCESS	Subscribe operation was successful.
SCRIPT_OPERATION_FAILED	Subscribe operation failed.
SCRIPT_NO_ACCESS	Bluetooth GATT client is not initialized.
SCRIPT_PARAM_INVALID	Could be one of the following: Incorrect connection id or connection is not present Characteristic or descriptor handle too high or too low. Incorrect subscription type

Function call example

#include <io>
#include <read>
#include <float>
#include <string>
#include <core>
#include <write>
#include <define>
#include <socket>
#include <bluetooth>

#define FIRST_CONNECTION       0
#define SECOND_CONNECTION      1

new peer_mac_address[] = [0xFF, 0x48, 0x80, 0x33, 0xE3, 0xA8];
new chr_val_handle = 0x0F;
new chr_val_ccc_handle = 0x10;

forward public callback (event);
public callback (event)
{
    switch(event)
    {
        case BT_NOTIFICATION_RX:
        {
            
        }
    }
    return 0;
}

main()
{   
    bt_init();
    bt_gatt_client_init();
    while (bt_gatt_client_connect(FIRST_CONNECTION, BT_ADDR_RANDOM, peer_mac_address) != SCRIPT_OPERATION_SUCCESS)
    {
        Delay(100);
    }
    bt_gatt_client_subscribe(FIRST_CONNECTION, chr_val_handle, chr_val_ccc_handle, BT_GATT_CCC_NOTIFY);
    for(;;)
    {
        Delay(100);
    }
}

Debug example

This example initializes BLE, then initializes GATT Client module, connects to peer device and subscribes to attribute. Example uses debug_print function to print information log to Initialized peripheral.

#include <io>
#include <read>
#include <float>
#include <string>
#include <core>
#include <write>
#include <define>
#include <socket>
#include <bluetooth>
#include <debug>

#define RS232_SPEED         115200
#define WORD_LENGTH         WORDLENGTH_8
#define STOP_BITS           STOPBITS_1
#define PARITY              PARITY_NONE

#define FIRST_CONNECTION       0
#define SECOND_CONNECTION      1

new peer_mac_address[] = [0xFF, 0x48, 0x80, 0x33, 0xE3, 0xA8];
new chr_val_handle = 0x0F;
new chr_val_ccc_handle = 0x10;
new return_code = SCRIPT_OPERATION_SUCCESS;

forward public callback (event);
public callback (event)
{
    switch(event)
    {
        case BT_NOTIFICATION_RX:
        {
            
        }
    }
    return 0;
}

main()
{
    Init(RS232, RS232_SPEED, WORD_LENGTH, STOP_BITS, PARITY);
    debug_init(RS232);
    return_code = bt_init();
    if (return_code != SCRIPT_OPERATION_SUCCESS)
    {
        // Handle failed bt_init here
        debug_print("bt_init failed\r\n");
    }
    else 
    {
        debug_print("bt_init succeeded\r\n");
    }
    return_code = bt_gatt_client_init();
    if (return_code != SCRIPT_OPERATION_SUCCESS)
    {
        // Handle failed bt_gatt_client_init here
        debug_print("bt_gatt_client_init failed\r\n");
    }
    else 
    {
        debug_print("bt_gatt_client_init succeeded\r\n");
    }
    debug_print("Connecting to a device with this MAC address: %X:%X:%X:%X:%X:%X\r\n", peer_mac_address[0], 
                peer_mac_address[1], peer_mac_address[2], peer_mac_address[3], peer_mac_address[4], peer_mac_address[5]);
    while (bt_gatt_client_connect(FIRST_CONNECTION, BT_ADDR_RANDOM, peer_mac_address) != SCRIPT_OPERATION_SUCCESS)
    {
        debug_print("bt_gatt_client_connect time-out\r\n");
        Delay(100);
    }
    debug_print("Connected successfully\r\n");
    return_code = bt_gatt_client_subscribe(FIRST_CONNECTION, chr_val_handle, chr_val_ccc_handle, BT_GATT_CCC_NOTIFY);
    if (return_code != SCRIPT_OPERATION_SUCCESS)
    {
        // Handle failed bt_gatt_client_subscribe here
        debug_print("bt_gatt_client_subscribe failed\r\n");
    }
    else 
    {
        debug_print("bt_gatt_client_subscribe succeeded\r\n");
    }
    for(;;)
    {   
        Delay(1000);
    }
}