Analog-to-digital converter in Due

Official Hardware Mega Due
1

i wrote a code to convert an analog signal to digital on Due. the results ,i am getting on the oscilloscope, of the ADC as shown in Frequency_5Hz (attached) for analog square wave = 1v at the pin( A1). fre = 5Hz.
and by increasing the frequency to 50Hz at scope Frequency_50Hz, the ADC seems like it can't catch up with the input signal.
the code i wrote is:

const int InputPin = A1;
const int OutPin = 28;

void setup()
{
pinMode(InputPin,INPUT);
pinMode(OutPin,OUTPUT);
analogReadResolution(12); // 12-bit!
Serial. begin(9600);
}
void loop() {

int a;

analogReadResolution(12); // 12-bit!
a = analogRead(InputPin);
digitalWrite(OutPin,a);
Serial.println(a);
while(0){
}
}

a confusing point is that in Frequency_5Hz i can see that ADC is responding but not correctly. i think that i should see a series of binaries not a plus looks similar to the input signal.

could anyone tell me why i am getting this

Best Wishes,

M,

Frequency_5Hz.png
Frequency_5Hz.png1360×577 40.6 KB

Frequency_50Hz.png
Frequency_50Hz.png1360×577 48.6 KB

2

I've already experimented it. I supose the ADC is not fast enough to do it because it´s a hardware problem. In order to solve it you problaby should select a faster microcontroler family.

3

the adc dac are both fast enough
take the print statement out the loop

4

the adc dac are both fast enough
take the print statement out the loop

i've tried that, but there was no change occur on the output

regards,

M,

5

guys do you know if there is a testing code for ADC to Due.

Best Wishes,

M,

6

try to add in setup code next line

REG_ADC_MR = (REG_ADC_MR & 0xFFF0FFFF) | 0x00020000;

this will make ADC much faster

and this function

inline void digitalWriteDirect(int pin, boolean val)  //fast writing to pin
{
  if(val) g_APinDescription[pin].pPort -> PIO_SODR = g_APinDescription[pin].ulPin;
  else    g_APinDescription[pin].pPort -> PIO_CODR = g_APinDescription[pin].ulPin;
}

and use it like

digitalWriteDirect(OutPin,a);

makes digitalwrite muuuuch faster