ADCInput not compatible with analogRead?

[baritonomarchetto]

Hello, I had success in sampling a sound wave from an analog input and then transfer it clean to an ADC (PT8211) thanks to ADCInput.
Now, I also want to make some modification to data recorded as a function of the position of a potentiometer.

I tryed the code below, but I have nothing at DAC out. Comment the Pot_Read() function in the loop and everithing works well (except for the analog read, obviously :) )

#include <I2S.h>
#include <ADCInput.h>

#define ADC_PIN A0
#define I2S_BCLK 2
//#define I2S_WS   3
#define I2S_DOUT 4

#define SAMPLE_RATE 32767 //MAX sample rate

int16_t value, dacLeft, dacRight;

int16_t POT_pin = A1;

int16_t potValue_raw;
int16_t pot_timer;

I2S i2s(OUTPUT);
ADCInput adc(ADC_PIN);

void setup() {
  i2s.setBCLK(I2S_BCLK); // Note: LRCLK (WS)= BCLK + 1
  i2s.setDOUT(I2S_DOUT);
  i2s.setBitsPerSample(16);
  i2s.setLSBJFormat();
  i2s.begin(SAMPLE_RATE);
  adc.begin(SAMPLE_RATE);
}

void loop() {
  while (adc.available()) {
    value = adc.read(); //12 bit -> 0–4095
    dacLeft = (value - 2048)<<4;//12 bit unsigned -> 16 bit signed (-32768 to +32767)
    i2s.write16(dacLeft, dacRight); // dend to DAC values for LEFT and RIGHT channeL
  }
  Pot_Read();
}

void Pot_Read(){
  pot_timer++;
  if(pot_timer > 200){ //to save resources switches are checked every tot cycles.
    pot_timer = 0;
    potValue_raw = analogRead(POT_pin); //0-4096
  }
}

Any hint?

Thanks in advance for the help!

[earlephilhower]

The ADC unit can be owned by either DMA or the CPU, not both. Doing analogReads while the DMA is set up is going to produce some very "interesting" results, none of which will be correct...

When you use ADCInput it goes to DMA control and is set up with a HW timer that automatically samples the channels set in the bitmask w/o any intervention, stuffing their values in a FIFO for DMA to deposit to RAM.

So, if you want to use another ADC input while doing ADCInput you'll just have to add that extra pin and use the ADCInput stream to look at it (i.e. 1st read() would be the mike, 2nd read() would be the pot, 3rd read() would be the mike, 4th read() the pot, etc.).

[baritonomarchetto]

Thanks Earle. By recording the second analog signal, is the sample rate halved, or is it kept at the set value (I mean: I now have double the values, so if the timing is fixed I will end with half audio values).
Hope it makes sense.

[earlephilhower]

Same effective rate. So if you pass in 8000hz and 2 inputs, the ADC will actually run at 16000hz and sample each of those 2 inputs at 8khz.