CODEWITHSUNDEEP
c++arduinoarduino-c++
GlumandaGandalf
GlumandaGandalf

Reputation: 27

SAMD21G18 ADC Freerunning Issues

I'm currently writing a Library for the ADC of the SAMD21G18. Everything works so far. But when I enable the Freerunning mode of the ADC with 1024 Samples the results differ from what I expect. Here is the code:

#include "ADC_MC.h"

#define Serial SerialUSB

ADC_MC adc;
void setup() {
  Serial.begin(9600);
  adc.init();
  adc.set_SETTINGS(0x05, INT1V, SAMPLENUM_1024, GAIN_2x);
  adc.set_FREERUN(true);
  adc.enable();
}
void loop() {
  int t1 = 0;
  int value;
  t1 = micros();
  value = adc.get_result();
  Serial.print("FREE T:" + String(micros() - t1) + " ");
  Serial.print(value);
  Serial.print("\t");
  //Serial.println(adc.get_ADC_SAMPLENUM());

  t1 = micros();
  value = adc.readPin_once(0x05, INT1V, SAMPLENUM_1024, GAIN_2x);
  Serial.print("1024S T:" + String(micros() - t1) + " ");
  Serial.print(value);
  Serial.print("\t");


  t1 = micros();
  value = adc.readPin_once(0x05, INT1V, SAMPLENUM_4, GAIN_2x);
  Serial.print("4S T:" + String(micros() - t1) + " ");
  Serial.print(value);
  Serial.print("\n");
  t1 = micros();

  adc.set_SETTINGS(0x05, INT1V, SAMPLENUM_1024, GAIN_2x);
  adc.set_FREERUN(true);
  adc.enable();
  delay(500);
}

The output is like this:

FREE T:12 3803  1024S T:19755 3806  4S T:105 3803
FREE T:12 3803  1024S T:19758 3805  4S T:105 3801
FREE T:12 3803  1024S T:19753 3805  4S T:105 3802
FREE T:11 3803  1024S T:19756 3805  4S T:105 3805
FREE T:12 3803  1024S T:19761 3805  4S T:105 3801

It appears that the result of the freerun is like the 4 Samples and not the 1024. Is there a max samplerate in the freerunning mode? If I check the current samplerate in freerunning it returns 1024 and looking at the amount of time it takes for one measurement in freerunning mode (~19733) it appears like its 1024. So why the discrepancy?

Upvotes: 0

Views: 22

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