Taking my Arduino project to development - Questions

Other Hardware Product Design
1

Thanks to @Grumpy_Mike, I came up with this sketch:

//Thanks to Grumpy_Mike and tuxduino on the Arduino.cc boards

unsigned long keyPrevMillis = 0;
const unsigned long keySampleIntervalMs = 25;

int redPin = 11;
int greenPin = 10;
int bluePin = 9;
int LEDcolor=0; // 0=White, 1=Red, 2=Orange, 3=Yellow, 4=Green, 5-Blue,  6=Purple, 7=Pink 
int LEDstatus =0; //0=Off, 1=On
int changed =0; //has the LEDstatus just changed?
byte longKeyPressCountMax = 80;    // 80 * 25 = 2000 ms
byte longKeyPressCount = 0;

byte prevKeyState = HIGH;         // button is active low
const byte keyPin = 2;            // button is connected to pin 2 and GND

// called when button is kept pressed for less than 2 seconds
void shortKeyPress() 
  {
    Serial.println("short");
    if (LEDstatus==1)
    {
    LEDcolor = LEDcolor +1;
    if (LEDcolor==8) {LEDcolor=0;}
    if (LEDcolor==0) {analogWrite(redPin, 0);analogWrite(greenPin, 0);analogWrite(bluePin, 0);Serial.println("White");}
    if (LEDcolor==1) {analogWrite(redPin, 0);analogWrite(greenPin, 255);analogWrite(bluePin, 255);Serial.println("Red");}
    if (LEDcolor==2) {analogWrite(redPin, 5);analogWrite(greenPin, 215);analogWrite(bluePin, 255);Serial.println("Orange");}
    if (LEDcolor==3) {analogWrite(redPin, 0);analogWrite(greenPin, 0);analogWrite(bluePin, 255);Serial.println("Yellow");}
    if (LEDcolor==4) {analogWrite(redPin, 255);analogWrite(greenPin, 0);analogWrite(bluePin, 255);Serial.println("Green");}
    if (LEDcolor==5) {analogWrite(redPin, 255);analogWrite(greenPin, 255);analogWrite(bluePin, 0);Serial.println("Blue");}
    if (LEDcolor==6) {analogWrite(redPin, 175);analogWrite(greenPin, 255);analogWrite(bluePin, 175);Serial.println("Purple");}
    if (LEDcolor==7) {analogWrite(redPin, 0);analogWrite(greenPin, 255);analogWrite(bluePin, 155);Serial.println("Pink");}
    }
    else
    {
      Serial.println("NOTHING");
    }
  }

// called when button is kept pressed for more than 2 seconds
void longKeyPress() 
  {
    Serial.println("long");
    if (LEDstatus==0 && changed==0)
    {
    if (LEDcolor==0) {analogWrite(redPin, 0);analogWrite(greenPin, 0);analogWrite(bluePin, 0);}
    if (LEDcolor==1) {analogWrite(redPin, 0);analogWrite(greenPin, 255);analogWrite(bluePin, 255);}
    if (LEDcolor==2) {analogWrite(redPin, 5);analogWrite(greenPin, 215);analogWrite(bluePin, 255);}
    if (LEDcolor==3) {analogWrite(redPin, 0);analogWrite(greenPin, 0);analogWrite(bluePin, 255);}
    if (LEDcolor==4) {analogWrite(redPin, 255);analogWrite(greenPin, 0);analogWrite(bluePin, 255);}
    if (LEDcolor==5) {analogWrite(redPin, 255);analogWrite(greenPin, 255);analogWrite(bluePin, 0);}
    if (LEDcolor==6) {analogWrite(redPin, 175);analogWrite(greenPin, 255);analogWrite(bluePin, 175);}
    if (LEDcolor==7) {analogWrite(redPin, 0);analogWrite(greenPin, 255);analogWrite(bluePin, 155);}
      changed=1;
      LEDstatus=1;Serial.println("On");
    }
    if (LEDstatus==1 && changed==0)
    {
      analogWrite(redPin, 255);
      analogWrite(greenPin, 255); 
      analogWrite(bluePin, 255);
      changed=1;
      LEDstatus=0;Serial.println("Off");
    }
    longKeyPressCount = 0;
  }

// called when key goes from not pressed to pressed
void keyPress() {
    Serial.print("key press / ");
    longKeyPressCount = 0;
}


// called when key goes from pressed to not pressed
void keyRelease() 
{
    Serial.println("key release");
    
    if (longKeyPressCount < longKeyPressCountMax && changed==0) {
          shortKeyPress();
}
changed=0;
}

void setup() 
  {
    Serial.begin(9600);
    pinMode(keyPin, INPUT);
    digitalWrite(keyPin, HIGH);
    pinMode(redPin, OUTPUT);
    pinMode(greenPin, OUTPUT);
    pinMode(bluePin, OUTPUT); 
    analogWrite(redPin, 255);
    analogWrite(greenPin, 255); 
    analogWrite(bluePin, 255);
  }

void loop() {
    // key management section
    if (millis() - keyPrevMillis >= keySampleIntervalMs) {
        keyPrevMillis = millis();
        
        byte currKeyState = digitalRead(keyPin);
        
        if ((prevKeyState == HIGH) && (currKeyState == LOW)) {
            keyPress();
        }
        else if ((prevKeyState == LOW) && (currKeyState == HIGH)) {
            keyRelease();
        }
        else if (currKeyState == LOW) {
            longKeyPressCount++;
        }

        prevKeyState = currKeyState;
    }
        if (longKeyPressCount >= longKeyPressCountMax) {
        longKeyPress();
            }
}

and it works exactly the way I want it to. I used it as an Arduino/breadboard prototype to show a PCB manufacturer EXACTLY what I want the product to do.

If I want the final product to be an open-source piece of equipment where anyone could hook up and modify the code, is there a chip that I should insist that the manufacturer uses? It looks like the AT Tiny45 would work, but I want to try and go SMALL if I can and just leave pins for hooking up to an Arduino.

Am I stuck with the AT Tiny45, or is there a better choice?

Edit:

I got the idea from this:

2

Since I don't know your project, you need to find a chip that can support your project. Looks like you need quite a few pins, so just make sure that you have enough pins that support what you want to do with them.

Are you ultimately wanting to design a PCB for this?

3

I watched the video. I don't like the initial assumption that saving money is a driver for hobby projects. If a $3 chip versus a $19 Arduino is a "lot of money" to save then you have bigger problems.

If this is supposed to be a board people can buy and reprogram themselves, then cost is a driver. If you can make them cheaper, you will sell them cheaper and you will sell a lot more. When your customers are looking in the store and they find two boards that will do what they want, almost everyone will choose the cheaper one, just because.

If you are going to make 20 of them for a school class, then the difference in price is much less. If you were to charge for your time programming and testing then the cost of the chips is totally insignificant. If you are volunteering your time, then making work for yourself by designing around a chip you've never touched is just going to consume more of your time.

My basic rule is never build a PCB in quantity until I have prototyped it. Most if the time I get the special sensor or whatever on a breakout board and breadboard it. If it is SMD only, then I make a PCB, but only one. If you've prototyped on an Uno with a 328P chip, then you should design a 328P chip into your PCB. You can get the SMD version to make your board smaller.