analogRead functionality for chipkit uC32

[andrewkhardy]

Hello and thanks for taking the time to read my question.  I'm hoping to use the ADC functionality of the chipkituC32 but I have some questions. As I understand it, when I write the command

Input = analogRead(A3)

I should get an interger number 1023 /3.3 = x . However when I have no input into the A3 port, I get the constant number 788. How do I do the correct conversion? When I was sending in a DC voltage of 2 V I was getting alternating numbers between 600 and 1023 which make no sense.

Also, I cannot find in the datasheet, what is the frequency to read in a signal? I found somewhere online that it was only 10kHz.  That seems incredibly low. IS the read frequency for digital signals higher? If I have a separate ADC and send a digital signal could I speed this up?  Thanks again

[JColvin]

Hi @andrewkhardy,
I'm not certain what the rest of your code is (in terms of viewing the result you received and the voltage conversion), but here is some example code that I used to test the analog conversion on a uC32. I would also recommend making sure that whatever you are using to supply to voltage has it's ground connected to the uC32 ground pin to create a common reference.

Spoiler

int value = 0;
float voltage = 0.0;

void setup() {
  // setting up
  Serial.begin(9600);
  pinMode(13, OUTPUT);
  
}

void loop() {
  // read in the analog input
  value = analogRead(A3);
  //blink an LED to see a visual change
  digitalWrite(13, HIGH);
  delay(value);
  digitalWrite(13, LOW);
  delay(value);
  //print out the measured ADC value
  Serial.print("value is: ");Serial.println(value);
  //convert the value that is between 0 and 1023 to a voltage scale
  voltage = float(value)/1023.0*3.3;
  Serial.print("voltage is: ");Serial.println(voltage);
}

 

With regards to the ADC itself, it is my understanding that the on-board ADC only runs up to 1 MSPS, though you can change some of the internal parameters detailed in this Microchip datasheet.

Let me know if you have any questions.

Thank you,
JColvin