How to send SAADC Data over BLE?

RE: How to send SAADC Data over BLE?

Kenneth — Wed, 07 Oct 2020 07:55:30 GMT

It doesn't seem as you are checking the error code from ble_nus_data_send()?

Best regards,
Kenneth

RE: How to send SAADC Data over BLE?

ENENER — Sat, 03 Oct 2020 14:16:36 GMT

Thank you.

So I tried like this.

void saadc_callback(nrf_drv_saadc_evt_t const * p_event)
{
	
	if (p_event->type == NRF_DRV_SAADC_EVT_DONE)
    {
        ret_code_t err_code;

        err_code = nrf_drv_saadc_buffer_convert(p_event->data.done.p_buffer, SAMPLES_IN_BUFFER);
        APP_ERROR_CHECK(err_code);

        int i;
        printf("ADC event number: %d\r\n", (int)m_adc_evt_counter);
		
        for (i = 0; i < SAMPLES_IN_BUFFER; i++)
        {
            printf("%d\r\n", p_event->data.done.p_buffer[i]);
        }
				   uint16_t BUFFER_SIZE = SAMPLES_IN_BUFFER * 2;
				
				err_code = ble_nus_data_send(&m_nus, (uint8_t *)p_event->data.done.p_buffer, (uint16_t *)BUFFER_SIZE, m_conn_handle);				
        m_adc_evt_counter++;
    }
}

There are no warning&errors.

But, I can't still receive any messages on my phone.

Can you find any problem??

Thank you.

RE: How to send SAADC Data over BLE?

haakonsh — Sat, 03 Oct 2020 13:27:26 GMT

I see it takes a pointer as the length argument. You need to declare a new variable and set its value to 2x SAMPLES_IN_BUFFER, then use the address of this variable as the length field.

RE: How to send SAADC Data over BLE?

ENENER — Sat, 03 Oct 2020 13:19:56 GMT

Thanks for your answer.

I tried your code, but there are 1 errors & warnings.

void saadc_callback(nrf_drv_saadc_evt_t const * p_event)
{
    if (p_event->type == NRF_DRV_SAADC_EVT_DONE)
    {
        ret_code_t err_code;

        err_code = nrf_drv_saadc_buffer_convert(p_event->data.done.p_buffer, SAMPLES_IN_BUFFER);
        APP_ERROR_CHECK(err_code);

        int i;
        printf("ADC event number: %d\r\n", (int)m_adc_evt_counter);

        for (i = 0; i < SAMPLES_IN_BUFFER; i++)
        {
            printf("%h\r\n", p_event->data.done.p_buffer[i]);
        }
				err_code = ble_nus_data_send(&m_nus, (uint8_t *)p_event->data.done.p_buffer[i], ((uint16_t *)SAMPLES_IN_BUFFER * 2), m_conn_handle);				
        m_adc_evt_counter++;
    }
}

..\..\..\main.c(701): warning: #181-D: argument is incompatible with corresponding format string conversion
printf("%s\r\n", p_event->data.done.p_buffer[i]);
..\..\..\main.c(703): error: #32: expression must have arithmetic type
err_code = ble_nus_data_send(&m_nus, (uint8_t *)p_event->data.done.p_buffer[i], ((uint16_t *)SAMPLES_IN_BUFFER * 2), m_conn_handle);
..\..\..\main.c: 1 warning, 1 error
".\_build\nrf52833_xxaa.axf" - 1 Error(s), 1 Warning(s).

Do you know how to solve this??

RE: How to send SAADC Data over BLE?

haakonsh — Sat, 03 Oct 2020 09:52:06 GMT

The only time you sample is if m_conn_handle is invalid. After you've triggered the sample task 5 times the saadc buffer is full and it's callback is called. At which point you ask the service to send data over over a non-existing connection, at which point you would haver gotten an error message if you'd checked your logs.

Also:

for (i = 0; i < SAMPLES_IN_BUFFER; i++)
        {
            printf("%d\r\n", p_event->data.done.p_buffer[i]);
						uint32_t err_code = ble_nus_data_send(&m_nus, (uint8_t *) p_event->data.done.p_buffer[i], (uint16_t *)SAMPLES_IN_BUFFER, m_conn_handle);
        }

This makes no sense, why are you using a for loop to send data when the APIs take a pointer and length parameter? You're transmitting a lot of unnecessary garbage, replace with:

for (i = 0; i < SAMPLES_IN_BUFFER; i++)
        {
            printf("%h\r\n", p_event->data.done.p_buffer[i]);
        }
uint32_t err_code = ble_nus_data_send(&m_nus, (uint8_t *) p_event->data.done.p_buffer[i], ((uint16_t *)SAMPLES_IN_BUFFER * 2), m_conn_handle);

Also, note that %d in a printf statement is a signed integer whereas the saadc samples are short signed integers, so you need to use %h instead.

You also need to double the length parameter in the call to ble_nus_data_send as the length is the number of bytes it will copy, starting from the given data pointer.