MCUdude/MegaCoreX

Analogue ports reading

ednieuw opened this issue · 2 comments

ednieuw commented

When the analogue port are defined with a number the readings of this port number is always 255.
When defining with an A before the port number results are fine.

The Arduino Every board compiles fine without the A.

In the coding example below the results of analogue port 2 is always 255
Like const int sensorPin = 2;

When
const int sensorPin = A2;
readings are fine

const int sensorPin = 2; //A2;         // Readings are now always 255
       // const int sensorPin = A2;    // Readings are now fine
int sensorValue = 0;                       // the sensor value

void setup() {  
 Serial.begin(9600);                     
 Serial.println("\n*********\nSerial started"); 
 #if defined(MEGACOREX)
      Serial.println("Compiled with MegaCore X"); 
 #else 
     Serial.println("Compiled with Arduino MegaAVR");   
#endif
}

void loop() {
sensorValue = analogRead(sensorPin);
Serial.print("LDR: ");
Serial.println(sensorValue);
delay(100);
}
MCUdude commented

I'll assume you're using the Nano Every?

When the analogue port are defined with a number the readings of this port number is always 255.
When defining with an A before the port number results are fine.

It's always to either use the digital pin number or use the A constants. The reason why you can't use 0 to 15 as analog pin values with the Nano Every makes perfect sense if you look at the pinout below.

Since MegaCoreX enables all available analog inputs to the user (unlike the official Arduino core), there are suddenly an overlap between the digital and analog pin number.

Does analogRead(3) means digital pin 3 or analog input 3? This is impossible for the compiler to determine.

However, on other pinouts where the analog pin numbers don't overlap the digital ones, like when using the 48-pin standard pinout, you can use analogRead(3) or any other number below 16, because none of the digital pins below 16 has analog input capabilities.

I hope this makes sense 🙂

ednieuw commented