configuring multiple saadc channels

[Masoumeh]

Hi,

I want to configure 2 channels of saadc in differential mode as follows:

void saadc_init(void) //ok
{
    ret_code_t err_code;

	nrf_saadc_channel_config_t channel_config1 =
        NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_DIFFERENTIAL(NRF_SAADC_INPUT_AIN4,NRF_SAADC_INPUT_AIN6);
	nrf_saadc_channel_config_t channel_config2 =
        NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_DIFFERENTIAL(NRF_SAADC_INPUT_AIN5,NRF_SAADC_INPUT_AIN7);

    err_code = nrf_drv_saadc_init(NULL, saadc_callback);
    APP_ERROR_CHECK(err_code);

    err_code = nrf_drv_saadc_channel_init(0, &channel_config1);
    APP_ERROR_CHECK(err_code);
		err_code = nrf_drv_saadc_channel_init(1, &channel_config2);
    APP_ERROR_CHECK(err_code);

    err_code = nrf_drv_saadc_buffer_convert(m_buffer_pool[0], SAMPLES_IN_BUFFER);
    APP_ERROR_CHECK(err_code);

    err_code = nrf_drv_saadc_buffer_convert(m_buffer_pool[1], SAMPLES_IN_BUFFER);
    APP_ERROR_CHECK(err_code);
		
		nrf_saadc_continuous_mode_enable(800);
	

}

But when I received data, it seems that only the channel that its channel index is zero is enabled. may you help me to find the issue and configure this 2 channel in scan mode? i am working based on the saadc example in sk17. 

[Masoumeh]

Thanks. where can I find the API documentation?

[Jørgen Holmefjord]

I linked to the documentation on the NRF_ESB_CREATE_PAYLOAD macro (https://infocenter.nordicsemi.com/topic/sdk_nrf5_v17.0.2/group__nrf__esb.html#ga4fc7d57ca9aa231677535e7beeddb72d).

[Masoumeh]

Hi, I still have this problem. I wanted to ask that how do samples save in buffers of ADC? I put every 12 bit of my data in 1.5 bytes and put all data together in a buffer and send it by ble(Line 154 to 172 ).  I wanna see if I understand the concept of adc savind format . 

[Jørgen Holmefjord]

Hi,

As mentioned in the SAADC peripheral documentation:

"Samples stored as 16-bit 2’s complement values for differential and single-ended sampling"

and:

"Results are stored in little-endian byte order in Data RAM. Every sample will be sign extended to 16 bit before stored in the Result buffer."

You may face issues if you use 12 bit resolution only send the lower 12 bits of the sample, for instance will the samples "-1" and "4095" have the same binary value (0b1111111111111111 - 0b0000111111111111).

Best regards,
Jørgen

[Masoumeh]

Thanks, it helped.