Set up ADC nrf52832 on a continuous transformation but it does not work.

RE: Set up ADC nrf52832 on a continuous transformation but it does not work.

Alex_Golubev — Tue, 11 Sep 2018 05:30:41 GMT

thanks.

RE: Set up ADC nrf52832 on a continuous transformation but it does not work.

Einar Thorsrud — Mon, 10 Sep 2018 07:51:54 GMT

There is no way to configure a cyclic data transfer in HW like this. The SAADC peripheral will fill up RAM via DMA, but you will get an event when the buffer is filled and have to provide a new buffer and start the process again to continue sampling. (This means that you will have some problems getting an accurate time between the last sample of one series and the first sample of the next series).

RE: Set up ADC nrf52832 on a continuous transformation but it does not work.

Alex_Golubev — Sat, 08 Sep 2018 05:30:43 GMT

Thanks for the answer.

increased buffer size NRF_SAADC->RESULT.MAXCNT = 64;

volatile int16_t result[64];
volatile float precise_result = 0;   

NRF_SAADC->CH[0].CONFIG = (SAADC_CH_CONFIG_GAIN_Gain1_2    << SAADC_CH_CONFIG_GAIN_Pos) |
                            (SAADC_CH_CONFIG_MODE_SE         << SAADC_CH_CONFIG_MODE_Pos) |
                            (SAADC_CH_CONFIG_REFSEL_VDD1_4 << SAADC_CH_CONFIG_REFSEL_Pos) |
                            (SAADC_CH_CONFIG_RESN_Bypass     << SAADC_CH_CONFIG_RESN_Pos) |
                            (SAADC_CH_CONFIG_RESP_Bypass     << SAADC_CH_CONFIG_RESP_Pos) |
                            (SAADC_CH_CONFIG_TACQ_40us        << SAADC_CH_CONFIG_TACQ_Pos);
     
    NRF_SAADC->CH[0].PSELP = SAADC_CH_PSELP_PSELP_AnalogInput0 << SAADC_CH_PSELP_PSELP_Pos;
    NRF_SAADC->CH[0].PSELN = SAADC_CH_PSELN_PSELN_NC << SAADC_CH_PSELN_PSELN_Pos;
    
    NRF_SAADC->RESOLUTION = SAADC_RESOLUTION_VAL_14bit << SAADC_RESOLUTION_VAL_Pos;
    
    NRF_SAADC->RESULT.MAXCNT = 64;
    NRF_SAADC->RESULT.PTR = (uint32_t)&result;
    
      // No automatic sampling, will trigger with TASKS_SAMPLE.
    NRF_SAADC->SAMPLERATE = 0x80 | SAADC_SAMPLERATE_MODE_Timers << SAADC_SAMPLERATE_MODE_Pos;
    
    NRF_SAADC->ENABLE = SAADC_ENABLE_ENABLE_Enabled << SAADC_ENABLE_ENABLE_Pos;
    
    NRF_SAADC->TASKS_CALIBRATEOFFSET = 1;
    while (NRF_SAADC->EVENTS_CALIBRATEDONE == 0);
    NRF_SAADC->EVENTS_CALIBRATEDONE = 0;
    while (NRF_SAADC->STATUS == (SAADC_STATUS_STATUS_Busy <<SAADC_STATUS_STATUS_Pos));
    
    NRF_SAADC->TASKS_START = 1;
    while (NRF_SAADC->EVENTS_STARTED == 0);
    NRF_SAADC->EVENTS_STARTED = 0;

    NRF_SAADC->TASKS_SAMPLE = 1;
    while (NRF_SAADC->EVENTS_END == 0);
    NRF_SAADC->EVENTS_END = 0;

The entire buffer is full 16380.

How to make cyclic data transfer ADC -> DMA -> RAM?

RE: Set up ADC nrf52832 on a continuous transformation but it does not work.

Einar Thorsrud — Thu, 06 Sep 2018 13:53:55 GMT

Hi,

The only problem I see is that you only have room for one sample in your result buffer, so it is not surprising that you do not get different samples. Try using a large buffer, and update NRF_SAADC->RESULT.MAXCNT accordingly.