STM32 with Arduino API (4/4): mini-controller

Your mini-controller will have three states:

- Potentiometer below the threshold: green color.
- Potentiometer above the threshold: red color.
- Button pressed: blue color, even if the potentiometer says something else.

The challenge is not just copying the program. By the end, you should have a
tested mini-controller: it reads an input, decides a state, changes the RGB LED,
writes evidence through Serial, and keeps one small improvement that you can
defend.

Before programming, think as if you were testing a small product. A good test
should say what you will touch, what color you expect to see, and what Serial
data would confirm that the controller made the correct decision.

The setRgb function avoids repeating three lines every time you want to change
color. The initial threshold is 600, but you will need to check whether it
makes sense with your real readings.

You will copy a base program, test it, and adjust it. The final result should be
a small but complete controller: it reads POT_1, decides with THRESHOLD,
allows manual mode with BUTTON_1, changes the RGB LED, and writes through
Serial which state it chose.

#include <Arduino.h>

const int POT_1 = PC0;
const int BUTTON_1 = PC5;  // Active LOW
const int RGB_RED = PA8;
const int RGB_GREEN = PA9;
const int RGB_BLUE = PA10;

const int THRESHOLD = 600;

void setRgb(int red, int green, int blue) {
  analogWrite(RGB_RED, red);
  analogWrite(RGB_GREEN, green);
  analogWrite(RGB_BLUE, blue);
}

void setup() {
  pinMode(BUTTON_1, INPUT);
  pinMode(RGB_RED, OUTPUT);
  pinMode(RGB_GREEN, OUTPUT);
  pinMode(RGB_BLUE, OUTPUT);
  Serial.begin(115200);
}

void loop() {
  int reading = analogRead(POT_1);
  bool buttonPressed = digitalRead(BUTTON_1) == LOW;
  const char* state;

  if (buttonPressed) {
    setRgb(0, 0, 255);
    state = "manual";
  } else if (reading >= THRESHOLD) {
    setRgb(255, 0, 0);
    state = "red";
  } else {
    setRgb(0, 180, 0);
    state = "green";
  }

  Serial.print("state=");
  Serial.print(state);
  Serial.print(" pot1=");
  Serial.print(reading);
  Serial.print(" button=");
  Serial.println(buttonPressed ? "pressed" : "released");

  delay(100);
}

Fill in the table after testing the controller. Each row must connect an input
with a decision and a piece of evidence. Use at least three rows and leave the
others blank if Teach shows more:

- Row 1: potentiometer below the threshold.
- Row 2: potentiometer above the threshold.
- Row 3: button 1 pressed to check manual mode.
- In Serial values seen, copy state, pot1, and button approximately.
- If you modify THRESHOLD, write the final value you used.

Choose one small improvement:

- Change the threshold.
- Change the colors or brightness.
- Make manual mode blink in blue.
- Add a Serial line that explains the state (green, red, or manual).