Bluetooth low energy

2 weeks ago

Hi Abishekh,

Thank you for your online forum question and your interest in our BLE products.

1. From the code shared it seems that you are using function uart_receive for the reception of the uart data. The buffer which stores the data (user_uart_data) is overwritten with new uart data but its previous value is never cleared, so if the length of the previous data written is bigger than the current one, some of the previous characters are passed on the new notification as well. A workaround for this would be to clear the user_uart_data buffer in user_app_uart_read before receiving new data and updating the notification value not periodically, but only when new data have been written to the UART.

2. You can add the read functionality to the characteristic using the following steps as a reference:

Taking the ble_app_peripheral example you can follow the steps below to read the value of the adc characteristic:

a. In file user_custs1_def.h change the database initialization of the SVC1_IDX_ADC_VAL_1_VAL field to:

    // ADC Value 1 Characteristic Value
    [SVC1_IDX_ADC_VAL_1_VAL]           = {SVC1_ADC_VAL_1_UUID_128, ATT_UUID_128_LEN, PERM(RD, ENABLE) | PERM(NTF, ENABLE),
                                             PERM(RI, ENABLE)|DEF_SVC1_ADC_VAL_1_CHAR_LEN, 0, NULL},

this will enable the read indication feature for the characteristic.

b. In file user_peripheral.c add the following to the case CUSTS1_VALUE_REQ_IND

case CUSTS1_VALUE_REQ_IND:
{
    struct custs1_value_req_ind const *msg_param = (struct custs1_value_req_ind const *) param;

    switch (msg_param->att_idx)
    {
        case SVC1_IDX_ADC_VAL_1_VAL:
	    {
	        user_svc1_read_adc_value_handler(msgid, msg_param, dest_id, src_id);
	    } break;

this will invoke a user created handler for the read request of the adc value.

c. In file user_custs1_impl.c add the implementation of the handler function 

void user_svc1_read_adc_value_handler(     ke_msg_id_t const msgid,
                                           struct custs1_value_req_ind const *param,
                                           ke_task_id_t const dest_id,
                                           ke_task_id_t const src_id)
{
    // As an example we increase value by five
    adc_value += 5;

    struct custs1_value_req_rsp *rsp = KE_MSG_ALLOC_DYN(CUSTS1_VALUE_REQ_RSP,
                                                        prf_get_task_from_id(TASK_ID_CUSTS1),
                                                        TASK_APP,
                                                        custs1_value_req_rsp,
                                                        DEF_SVC1_ADC_VAL_1_CHAR_LEN);

    // Provide the connection index.
    rsp->conidx  = app_env[param->conidx].conidx;
    // Provide the attribute index.
    rsp->att_idx = param->att_idx;
    // Force current length to zero.
    rsp->length  = sizeof(adc_value);
    // Provide the ATT error code.
    rsp->status  = ATT_ERR_NO_ERROR;
    // Copy value
    memcpy(&rsp->value, &adc_value, rsp->length);
    // Send message
    ke_msg_send(rsp);
}

3.  When writing to a characteristic as a BLE peer, the case CUSTS1_VAL_WRITE_IND will be invoked in user_catch_rest_hndl in file user_peripheral.c. You can create a new subcase for when the characteristic in question has been written e.g. SVC1_IDX_ADC_VAL_1_VAL

case CUSTS1_VAL_WRITE_IND:
{
  struct custs1_val_write_ind const *msg_param = (struct custs1_val_write_ind const *)(param);

  switch (msg_param->handle)
  {
    case SVC1_IDX_ADC_VAL_1_VAL:
      user_svc1_adc_wr_ind_handler(msgid, msg_param, dest_id, src_id);
      break;

Now user defined function user_svc1_adc_wr_ind_handler will be invoked when data is written by a BLE peer. You can add code inside user_svc1_adc_wr_ind_handler which will take the value written by the BLE peer and print it in the UART (similar to how user_svc1_led_wr_ind_handler uses the value written by the BLE peer to turn the LED on/off).

Best regards,
AA_Dialog

2 weeks ago

Hi Abishekh,

Please check the uart example of our SDK6 that can be found under

...\DA145xx_SDK\6.0.16.1144\projects\target_apps\peripheral_examples\uart

and in particular files uart_receive_examples.c and uart_loopback_examples.c which contain functions that showcase different ways for receiving data from the UART. Note that you can use the uart_register_rx_cb api to register a callback function for the UART receive event when you are using UART in UART_OP_INTR mode. As an example the uart_loopback_interrupt_example registers function uart_read_cb for the receive event. After that it calls uart_receive with a length of one byte. When this byte is received uart_read_cb is invoked which in turns adds this byte to the ring buffer and calls uart_receive again, waiting for the next character reception from UART. You can use these examples as a reference to help you implement UART handling for your application.

Best regards,
AA_Dialog