Analog I/O Pins and ADC Sampling Frequency

Hardware Arduino Due
4

Ok, here's some testings I made, I really don't know what I'm doing, but if someone assures me there's no danger of frying my board with this, I'll be happy... see my comments:

#define MAX_ADC_RESOLUTION 10 //changing resolution doesn't seem to affect sampling rate speed in this test

void setup() {

//I tested this with a hall sensor, not sure if results will vary according to the sensor used, but please be gentle with me, I just started learning this 3 days ago, I'm just an amateur programmer. :slight_smile:

Serial.begin(9600);

//check adc.h in the /sam folder

analogReadResolution(MAX_ADC_RESOLUTION); //

//by default, I get around 25000 samples per second, readings around 570 ( 10bit ) with a hall sensor plugged in

//adc_init(ADC, SystemCoreClock, ADC_FREQ_MAX2, 1); //~313000 samples per second, A/D readings kaput
//adc_init(ADC, SystemCoreClock, ADC_FREQ_MAX2, 2); //~288 000 samples per second, A/D readings now have about 10% deviation
adc_init(ADC, SystemCoreClock, ADC_FREQ_MAX2, 3); //~267000 samples per second, A/D readings OK, the best compromise I got
//adc_init(ADC, SystemCoreClock, ADC_FREQ_MAX2, 4); //~220000 samples per second, A/D readings OK
//adc_init(ADC, SystemCoreClock, ADC_FREQ_MAX2, ADC_STARTUP_NORM ); //~65000 samples per second,A/D readings OK
//adc_init(ADC, SystemCoreClock, ADC_FREQ_MAX2, ADC_STARTUP_FAST ); //~47000 samples per second, from the name, I was tempted to think this would perform better. But I know nothing.

edit: correction, I missed that 4 bit part from Dave's documentation. :-/

pinMode(ADC0,INPUT);
}

void loop() {

int start = millis();
int num_samples = 0;

//just to evaluate any possible accurancy degradation while messing around with this
int value = 0;
int max_value = 0;
int min_value = 2^MAX_ADC_RESOLUTION;

//let's see how many samples we can read in 1 second
while( millis() - start < 1000 )
{
value = analogRead(ADC0);

if(value > max_value )
max_value = value;

if(value < min_value )
min_value = value;

num_samples++;
}

// print out the control results
Serial.println("\nsamples read: ");
Serial.print(num_samples);

Serial.println("\nMax value: ");
Serial.print( max_value );

Serial.println("\nMin value: ");
Serial.print( max_value );

delay(1000);
}

Any thoughts?