NRF52 SAADC never writes result to buffer

RE: NRF52 SAADC never writes result to buffer

Simonr — Mon, 19 Jul 2021 12:51:37 GMT

What SDK version, and if relevant SoftDevice version are you using in this application? Have you already gotten it to work on a DK or similar, and are now struggling to get the project running on your custom board?

Best regards,

Simon

RE: NRF52 SAADC never writes result to buffer

khorght — Sun, 18 Jul 2021 21:07:30 GMT

nRF52832-QFAA-R7

RE: NRF52 SAADC never writes result to buffer

Dmitry — Sun, 18 Jul 2021 19:27:35 GMT

Umm, cannot say anything helpful.. What chip do you have? Your code works on my 52840 DK (without interrupts for simplicity, but it shouldn't matter), adc_result is filled with VDD:

static uint16_t adc_result= 0xaaaa;

//NRF_SAADC->CH[0].PSELP = SAADC_CH_PSELP_PSELP_AnalogInput0 << SAADC_CH_PSELP_PSELP_Pos;
NRF_SAADC->CH[0].PSELP = SAADC_CH_PSELP_PSELP_VDD << SAADC_CH_PSELP_PSELP_Pos;
// AIN0 as Negative for differential channel
NRF_SAADC->CH[0].PSELN = SAADC_CH_PSELN_PSELN_NC << SAADC_CH_PSELN_PSELN_Pos;
//ADC range = 0.6V/(1/6) = 3.6V
NRF_SAADC->CH[0].CONFIG = (SAADC_CH_CONFIG_GAIN_Gain1_6 << SAADC_CH_CONFIG_GAIN_Pos) |
(SAADC_CH_CONFIG_REFSEL_Internal << SAADC_CH_CONFIG_REFSEL_Pos) |
(SAADC_CH_CONFIG_MODE_SE << SAADC_CH_CONFIG_MODE_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_3us << SAADC_CH_CONFIG_TACQ_Pos);
while (NRF_SAADC->STATUS & 0x01); // Wait while ADC busy
NRF_SAADC->SAMPLERATE = SAADC_SAMPLERATE_MODE_Task << SAADC_SAMPLERATE_MODE_Pos;
NRF_SAADC->RESOLUTION = SAADC_RESOLUTION_VAL_14bit << SAADC_RESOLUTION_VAL_Pos;
NRF_SAADC->RESULT.PTR = (uint32_t) &adc_result; // Pointer to result variable
NRF_SAADC->RESULT.MAXCNT = 1;

NRF_SAADC->ENABLE = 0x01;

NRF_SAADC->EVENTS_STARTED = 0;
NRF_SAADC->TASKS_START = 1;
while (! NRF_SAADC->EVENTS_STARTED) {}

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

RE: NRF52 SAADC never writes result to buffer

khorght — Sun, 18 Jul 2021 18:09:07 GMT

Thanx for the advice, Dmitry. This isn't working too. i've already tryed:

uint32_t adc_result;

NRF_SAADC->RESULT.PTR = (uint32_t ) &adc_result;

then volatile uint32_t adc_result;

then int adc_result;

and volatile int adc_result;

then uint16_t adc_result;

and volatile uint16_t adc_result;

and tryed to use SDK with

static nrf_saadc_value_t m_buffer_pool[2][2];

if my code based on just reading datasheet and poor programming knowledge may be incorrect, then with SDK it should work flawlessly, because my intrusion is as minimal as possible, i've just copied lines from example and SDK should do all the magic with buffering/double buffering but it gives me the very same result - nothing written to buffer when (p_event->type == NRF_DRV_SAADC_EVT_DONE).

The biggest question is - why i can't just get the result from some sort of ADCRESULT register as i did with STM32, LPC, MKL03Z, MSP432, EFM32 if i don't need/want/can using DMA.

RE: NRF52 SAADC never writes result to buffer

Dmitry — Sun, 18 Jul 2021 15:17:43 GMT

Hi,

[quote userid="106295" url="~/f/nordic-q-a/77608/nrf52-saadc-never-writes-result-to-buffer"]i've tryed to use adc_result as uint32_t, as int, as volatile [/quote]

Is it a plain variable, not an array? then you should write NRF_SAADC->RESULT.PTR = (uint32_t ) &adc_result;

A sample is a signed 16-bit value, so adc_result should be "short" or "int16_t".