Arduino Nano - Why are my pins behaving the way they are? - c++

Question

I have a device that measures radiation, using an Elegoo Uno (knockoff Arduino brand) and an RM-60 Radiation Monitor from Aware Electronics. I have had this working for almost a year and a half as part of a high-altitude balloon payload item at my university. I am currently revisiting it, as now I want to understand and cleanup my code.
The setup goes like this:
The RM-60 has four wires. Yellow and black go to ground, red to my 5v, and the green goes to my output (More documentation can be found online).
I have a pin attached to digital 2. I had read online that pins 2 & 3 can use attachInterrputs for the Uno. But for whatever reason, setting my pinMode() to 2 won't work. I have found that when I set my pin to 8, with my actual wire connecting to digital 2, I can read it fine.
This is what I am confused about. I felt that after learning how these inputs work, I am doing it right. But it's not working. So then why, when my pin set to 8, is the device running correctly? If I am doing this wrong (or inefficiently), what tips or pointers can you give me on how to optimize/repair this?
I have my previous code, compiled and tested from almost two years ago. It works as is, but I just don't understand why. I have looked online for similar projects, as several balloon teams around the world have used RM-60s to measure radiation. Following their pin layout and program, I have been unsuccessful.
//this is taking just the necessary lines to run the geigercounter.
//using geigerPin 8, it works. But why not when I change this to 2, where my
//wire actually is?
int count;
int geigerPin = 8;
int testVar = 0;
void setup() {
Serial.begin(9600);
pinMode(geigerPin, OUTPUT);
attachInterrupt(0, test, RISING);
}
void loop() {
// put your main code here, to run repeatedly:
Serial.println(count * 6);
count = 0;
delay(10000);
}
void test() {
count++;
}
The data reads back to the Serial monitor every 10 seconds. The returned result should be the counts over ten seconds, multiplied by 6 to give us a counts-per-minute reading.

Answer 1

Please refer to the manual befor using any functions. The manual clearly states that your approach is not going to work.
From the Arduino Reference Manual:
attachInterrupt(digitalPinToInterrupt(pin), ISR, mode) (recommended)
attachInterrupt(interrupt, ISR, mode) (not recommended)
attachInterrupt(pin, ISR, mode) (Not recommended. Additionally, this
syntax only works on Arduino SAMD Boards, Uno WiFi Rev2, Due, and
101.)
Example Code
const byte ledPin = 13;
const byte interruptPin = 2;
volatile byte state = LOW;
void setup() {
pinMode(ledPin, OUTPUT);
pinMode(interruptPin, INPUT_PULLUP);
attachInterrupt(digitalPinToInterrupt(interruptPin), blink, CHANGE);
}
void loop() {
digitalWrite(ledPin, state);
}
void blink() {
state = !state;
}