bt_gatt_client_read()

Description

Function reads data from a specific attribute via handle.

Syntax

bt_gatt_client_read(connection_id, handle, offset, read_len, data_array[]);

Parameters

Variable	Input

Variable	Input
`connection_id`	Connection id which was described in `bt_gatt_client_connect` function. Could be either 0 or 1.
`handle`	Handle of attribute to read data from. Handle limits are from 0x0001 to 0xFFFF.
`offset`	Data offset.
`read_len`	Returned amount of data that’s been read in bytes. This is NOT the amount of data to read, this is the amount of data that’s been read. User should pass a variable here, not a number.
`data_array[]`	Data array where read data will be stored. If the returned data exceeds the array's capacity, it will be truncated to fit.

Returns

Return value	Return explanation
SCRIPT_OPERATION_SUCCESS	Read operation was successful.
SCRIPT_OPERATION_FAILED	Read 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 Handle too high or too low. Passed data array is smaller than requested read length.

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 handle_to_read_from = 0x0D;
new data_read_offset = 0;
new number_of_bytes_read = 0;
new read_data_array[20];

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_read(FIRST_CONNECTION, handle_to_read_from, data_read_offset, number_of_bytes_read, read_data_array);
    for(;;)
    {
        Delay(100);
    }
}

Debug example

This example initializes BLE, then initializes GATT Client module, connects to peer device and reads data from an 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 handle_to_read_from = 0x0D;
new data_read_offset = 0;
new number_of_bytes_read = 0;
new read_data_array[20];
new return_code = SCRIPT_OPERATION_SUCCESS;

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_read(FIRST_CONNECTION, handle_to_read_from, data_read_offset, number_of_bytes_read, read_data_array);
    if (return_code != SCRIPT_OPERATION_SUCCESS)
    {
        // Handle failed bt_gatt_client_read here
        debug_print("bt_gatt_client_read failed\r\n");
    }
    else 
    {
        debug_print("bt_gatt_client_read succeeded\r\n");
        debug_print("Read data: ");
        for (new i = 0; i < number_of_bytes_read; i++)
        {
            debug_print("%02X ", read_data_array[i]);
        }
        debug_print("\r\n")
        
    }
    for(;;)
    {   
        Delay(1000);
    }
}