Hi, I'm working on a simple SAADC acquire in scan mode.
I create the two following function:
void adc_init(){
// Configure SAADC singled-ended channel 0, Internal reference (0.6V) and 1/6 gain.
NRF_SAADC->CH[0].CONFIG = (SAADC_CH_CONFIG_GAIN_Gain1_6 << SAADC_CH_CONFIG_GAIN_Pos) |
(SAADC_CH_CONFIG_MODE_SE << SAADC_CH_CONFIG_MODE_Pos) |
(SAADC_CH_CONFIG_REFSEL_Internal << 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_3us << SAADC_CH_CONFIG_TACQ_Pos);
// Configure the SAADC channel with VDD as positive input, no negative input(single ended).
NRF_SAADC->CH[0].PSELP = SAADC_CH_PSELP_PSELP_VDD << SAADC_CH_PSELP_PSELP_Pos;
NRF_SAADC->CH[0].PSELN = SAADC_CH_PSELN_PSELN_NC << SAADC_CH_PSELN_PSELN_Pos;
// Configure SAADC singled-ended channel 1, GPIO PIN Internal reference (0.6V) and 1/3 gain.
NRF_SAADC->CH[1].CONFIG = (SAADC_CH_CONFIG_GAIN_Gain1_6 << SAADC_CH_CONFIG_GAIN_Pos) |
(SAADC_CH_CONFIG_MODE_SE << SAADC_CH_CONFIG_MODE_Pos) |
(SAADC_CH_CONFIG_REFSEL_Internal << 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_3us << SAADC_CH_CONFIG_TACQ_Pos);
// Configure the SAADC channel with VDD as positive input, no negative input(single ended).
NRF_SAADC->CH[1].PSELP = SAADC_CH_PSELP_PSELP_AnalogInput6 << SAADC_CH_PSELP_PSELP_Pos;
NRF_SAADC->CH[1].PSELN = SAADC_CH_PSELN_PSELN_NC << SAADC_CH_PSELN_PSELN_Pos;
// Configure the SAADC resolution.
NRF_SAADC->RESOLUTION = SAADC_RESOLUTION_VAL_12bit << SAADC_RESOLUTION_VAL_Pos;
// Configure result to be put in RAM at the location of "result" variable.
NRF_SAADC->RESULT.MAXCNT = 2;
NRF_SAADC->RESULT.PTR = (uint32_t)&adc_result;
// No automatic sampling, will trigger with TASKS_SAMPLE.
NRF_SAADC->SAMPLERATE = SAADC_SAMPLERATE_MODE_Task << SAADC_SAMPLERATE_MODE_Pos;
// Enable SAADC (would capture analog pins if they were used in CH[0].PSELP)
NRF_SAADC->ENABLE = SAADC_ENABLE_ENABLE_Enabled << SAADC_ENABLE_ENABLE_Pos;
// Calibrate the SAADC (only needs to be done once in a while)
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));
}
uint32_t adc_read(){
// Start the SAADC and wait for the started event.
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;
nrf_delay_us(5); //with delay less than 5 us the firmware stop to work
// Stop the SAADC, since it's not used anymore.
NRF_SAADC->TASKS_STOP = 1;
while (NRF_SAADC->EVENTS_STOPPED == 0);
NRF_SAADC->EVENTS_STOPPED = 0;
return (adc_result);
}
I was able to init and read the adc without problem.
If I remove the 5 us delay in the read_adc() funciton the firmware stop to work.
In debug mode it works also without the delay, if I add any log line in the read adc funtion it works also without the delay.
Is it correct this behaviour? How I can understand more about this behaviour?
Thanks.
