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Task 2: Write a Program

Let’s break down this week’s assignment

  • Write a program for a microcontroller development board that you made - Quentorres Board from Week 4
  • to interact (with local input &/or output devices) - This is arbitrary. I chose to do a simple Button (Input) LED Diode (Output) Interaction
  • communicate (with remote wired or wireless devices)

At the time of writing this down… I am still in the progress of milling my new QuenTorres Board. So I thought my line of working this week would have to be

  1. Simulate Quentorres Board
  2. Programming
  3. Embed the program into the freshly milled and stufffed Quentorres Board.

Simulating Quentorres Board in Wokwi

To head start first as I am still having problems with producing my Quentorres board, I thought I will simulate the board first in Wokwi. The XIAO RP2040 is a microcontroller that is powered by the Raspberry Pi 2040 chip. It is an alternative to the Pi Pico - differences are the XIAO has lesser GPIO (general-purpose input/output) pins. So in Wokwi - I chose the Pi Pico to simulate the XIAO micro controller. alt text

Firstly. I look at the schematics of the Quentorres board - to figure out the placement of the components in my simulated board alt text

Then I compare the XIAO board and the Pi Pico to figure out the right GPIO configuration and connections.

alt text alt text

To compare is important. In XIAO, the LED & Switch is at D0,D1 - but as we see in the Pi Pico, GPIO 0 & 1 has functions reserved for the UART(universal asynchronous receiver-transmitter) interface. So instead, I connect with the GPIO Arduino Value if the XIAO controller into the Pi Pico- LED at 26, Button Switch at 27 (but I reckon any GPIO output works s long it is not reserved for special functions....).

The simulated board and components looks like this alt text

Programming

// UNDERSTANDING THE LAYERS OF PROGRAMMING WITH ARDUINO IDE (C/C++) //

  1. Libraries: code that have been developed for specific purpose - packaged for specifically working with particular hardwares or functions.
  2. Variables: A variable is a place to store a piece of data. It has a name, a value, and a type. Think of it like a container that has all the particular tools needed (declared) to make your code runs. Structure is usually Type Name = Value
  3. Function
    1. Set up: code to run once in the start/set up
    2. loop: main code function that runs repeatedly
      1. Control Structure: order in which individual statements, instructions or function calls of an imperative program are executed or evaluated.

Watch more from here:

Before we start coding… it is always good to break down how we envision the code to function. For this week’s assignment in my case… since there is a component of communication… I want to make a grumpy LED light that doesn’t want to be disturbed. I see the functions as following

Pressing the Switch

  1. Board tells me in the beginning “DO NOT PRESS”
  2. If button is pressed
  3. LED light turns on
  4. Board responds back with “TURN ME OFF” based on the lightstate ON
  5. If button is pressed again
  6. LED light turns off
  7. Board responds with “THANK YOU. DO NOT PRESS” when the state of light is OFF

Sending command

  1. Board tells me in the beginning “DO NOT PRESS”
  2. If I type a command and send
  3. LED light turns on
  4. Board responds back with “TURN ME OFF”
  5. I type a command and send again
  6. LED light turns off
  7. Board responds with “THANK YOU. DO NOT PRESS” when the state of light is OFF

This are my lines of code, inspired by this tutorial 

//Define the pin numbers for LED & Button Switch
const int ledPin = 26; //Based on the Arduino GPIO Pin of RP2040
const int swPin = 27; //Based on the Arduino GPIO Pin of RP2040

//Define variable to keep track of the state of LED (ON or OFF).
bool lightState = false;
//LED default state is OFF
//Boolean because there are two states ON (HIGH,TRUE,1) or OFF(LOW,FALSE,0)

void setup() {

  //Button is Input, LED is Output
  pinMode(ledPin, OUTPUT);
  pinMode(swPin, INPUT);

  Serial.begin(9600);
  Serial.setTimeout(10);
  Serial.println("DO NOT PRESS");
// For Communication Mode. Serial communication is initialized on Serial with a baud rate of 9600, and a timeout of 10 milliseconds.
// The board starts with "Do Not Press". 
// You can pull up the Serial Monitor in ArduinoIDE to do Serial Communication
}

void loop() {

 // Check if there is data available
  if (Serial.available() > 0) {
  // Read the incoming data - which is in the form of message so - String
    String s = Serial.readString();
    Serial.print("YOU: ");
    Serial.println(s);

    // When array is received, the LED light toggles (ON or OFF)
    lightState = !lightState;

    // Update the LED
    digitalWrite(ledPin, lightState);

    // if LED light is ON, board communicates with "turn me off". If turned OFF "thank you. do not press"
    if (lightState == HIGH) {
      Serial.println("TURN ME OFF");
    } else {
      Serial.println("THANK YOU. DO NOT PRESS");
    }

  }
  // Check if Button is pressed
  if (digitalRead(swPin) == HIGH) {

      // When button is pressed, the LED light toggles (ON or OFF)
      lightState = !lightState;

      // Update the LED
      digitalWrite(ledPin,lightState);
      delay (250);

    // if LED light is ON, board communicates with "turn me off". If turned OFF "thank you. do not press"
    if (lightState == HIGH) {
      Serial.println("TURN ME OFF");
    } else {
      Serial.println("THANK YOU. DO NOT PRESS");
    }

}
Simulation

Embedding the Program into the Quentorres Board

Interact

When I press the button, the light turns on - but the board will ask to turn off and to not press, so if you press once again it will turn off.

When I type a command, the LED light will turn on and typing another command will turn the LED off