Sending 32 bit of data from nrf52 ble moble app onto nrf52833

[amey3]

Hi,

I have used "write_handler(p_ble_evt->evt.gap_evt.conn_handle, p_rtc_service, p_evt_write->data[0]);" to send data to nrf52832 from nrfconnect mobile app but iam able to send  1 byte data as it is meant to be predefined in the gatts structure .

/*brief Event structure for @ref BLE_GATTS_EVT_WRITE. */
typedef struct
{
uint16_t handle; /**< Attribute Handle. */
ble_uuid_t uuid; /**< Attribute UUID. */
uint8_t op; /**< Type of write operation, see @ref BLE_GATTS_OPS. */
uint8_t auth_required; /**< Writing operation deferred due to authorization requirement. Application may use @ref sd_ble_gatts_value_set to finalize the writing operation. */
uint16_t offset; /**< Offset for the write operation. */
uint16_t len; /**< Length of the received data. */
uint8_t data[1]; /**< Received data. @note This is a variable length array. The size of 1 indicated is only a placeholder for compilation.
 */
} ble_gatts_evt_write_t;

In many nordic forum told that  you have to split the 32 bit data into an array of uint8_t(s) and and set that array equal to ble_gatts_evt_write_t ->data. ble_gatts_evt_write_t ->len .

But my query is that when i putting the value in nrf connect app  in unknown characteristics and write the value there as in uint32_t form for eg:653655  and the recieving the data in nrf52833 as 

p_evt_write->data[0] which is uint8_t  data[0]  unable to receive the data properly.please give the example or what changes i have to do so that receive the data properly.

[Sigurd]

Hi,

How did you Initialize this characteristic?

What did you set add_char_params.max_len  / attr_char_value.max_len to ?

Example snippet from LBS service:

    // Add LED characteristic.
    memset(&add_char_params, 0, sizeof(add_char_params));
    add_char_params.uuid             = LBS_UUID_LED_CHAR;
    add_char_params.uuid_type        = p_lbs->uuid_type;
    add_char_params.init_len         = sizeof(uint8_t);
    add_char_params.max_len          = sizeof(uint8_t);
    add_char_params.char_props.read  = 1;
    add_char_params.char_props.write = 1;

    add_char_params.read_access  = SEC_OPEN;
    add_char_params.write_access = SEC_OPEN;

    return characteristic_add(p_lbs->service_handle, &add_char_params, &p_lbs->led_char_handles);

[amey3]

i have set add_char_params.max_len as 50; do  i have to change add_char_params.max_len  to set as size of (uint32_t).please  reply me

[Sigurd]

p_evt_write->data[0] which is uint8_t  data[0]  unable to receive the data properly.

 You can find the length of the data in p_evt_write->len , then based on this, you can find the rest of the data in p_evt_write->data[0], p_evt_write->data[1], p_evt_write->data[2], p_evt_write->data[3] , etc.  As mentioned in ble_gatts_evt_write_t, uint8_t data[1]; /**< Received data. @note This is a variable length array. The size of 1 indicated is only a placeholder for compilation.