Embedded Programming

Goals

Group assignment:

• Demonstrate and compare the toolchains and development workflows for available embedded architectures.
• Document your work to the group work page and reflect on your individual page what you learned.

Individual assignment:

• Browse through the datasheet for your microcontroller
• Write a program for a microcontroller, and simulate its operation, to interact (with local input &/or output devices) and communicate (with remote wired or wireless connection)

Prior Knowledge

Before Fab, we learned to code Arduino, ATTINY, ESP32C3, and other microcontroller types. We also improved our through-hole soldering. Although taking Electrical Engineering certainly helps, the task is a bit daunting.

Projected Timeline

• Wednesday
  • Correct prior documentation
• Thursday
  • Start group assignment
• Friday
  • Finish group assignment
• Saturday
  • Start individual assignment
• Sunday
  • Finish individual assignment
• Monday
  • Get ahead
• Tuesday
  • Get ahead

Actual Timeline

• Wednesday
  • Correct prior documentation
• Thursday
  • Fix image compression issue
• Friday
  • Document image compression issue
• Saturday
  • Start group assignment
  • Finish group assignment
• Sunday
  • Document
• Monday
  • Start individual assignment
• Tuesday
  • Finish individual assignment

Group Assignment

I was in a group with Andrew Puky, Wilson Zheng, and Zaina Gibrine. I was assigned the ATtiny-412 documentation.

You can see our documentation on our group site.

Individual Assignment

ESP32C3

Wokwi

The Xiao ESP32-S3 seemed reasonable since I have experience from Electrical Engineering. I started by making and programming a Wokwi simulation. I edited the Wokwi template to make the code. I decided that, as well as the basic pulldown resistor configuration, I would add a second LED and program them to alternate when pressing the button.

• Wire

  • Delete third LED
  • Color code (5V red, GND black, misc green)
  • Add button
  • Add resistor
    

• Void setup

  • Serial begin 115200
  • Establish pinMode input for pin connected to button
  • Establish pinMode output for LED pins
    

• Void loop

  • Set button variable to digitalRead
  • Create if else loop
  • Set to if (variable) = HIGH
  • digitalWrite one pin as high, the other low
  • Alternate for else loop
    

While the wiring was generally trial and error, I did reference Kathryn Wu’s documentation since I noticed we used the same microcontroller.

• Simulate
  • Add desired features
  • Fix errors
  • Click play button
    
    

I did realize that when I set the loop, I never changed the pins according to their pinMode. Only one LED worked as a result, I was using one output and one input when I needed to use both output pins. This was an easy fix. I also programmed D0 to recieve high voltage when D1 recieves low and vice versa.

C++ Sample Program

I never brought the button and extra LED home, so I would have to use the blink example code first. Still, the steps were generally the same.

• Arduino code
  • Paste original code
  • Compile
    
    
• Install libraries and packages
  
  
• Modify specifications
  • Change board
  • Plug in
  • Add port
    
    I realized that Arduino was not picking up my board because the official Espressif esp32 package was not installed. After fixing this, I could set the board to ESP32-S3 XIAO Dev Model. It blinked without any errors. Once I get the necessary components, I will test the program for my pushbutton circuit.

C++ Source Code

pinMode(1, OUTPUT);
pinMode(2, OUTPUT);
pinMode(3, INPUT); 
}

void loop() {
    int button = digitalRead(3);

    if (button == HIGH) {
      digitalWrite(1, LOW);
    digitalWrite(2, HIGH);
    } else {
    digitalWrite(1, HIGH);
     digitalWrite(2, LOW);
     }
    delay(50);
}

MicroPython Program

At the lab, I managed to wire the circuit with all the required components. I asked ChatGPT for basic commands with the intention of putting them together based on my C++ file. However, I found an error with the computer not recognizing the machine command. It turned out that I had to download the firmware for the specific microcontroller and run a command using the file path.

• Use MicroPython
  • Download Thonny
  • Flash microcontroller .bin file
  • Add code
    

MicroPython Source Code

import time
import board
import digitalio

led1 = digitalio.DigitalInOut(board.D0)
led1.direction = digitalio.Direction.OUTPUT
led2 = digitalio.DigitalInOut(board.D1)
led2.direction = digitalio.Direction.OUTPUT
button = digitalio.DigitalInOut(board.D2)
button.direction = digitalio.Direction.INPUT
button.pull = digitalio.Pull.DOWN

while True:
    if not button.value:
        led1.value = True
        led2.value = False
    else:
        led1.value = False
        led2.value = True

    time.sleep(0.1)

RP2040

Wokwi

Everyone was using the Raspberry Pi Pico model since they had no XIAO RP2040, so I did the same. I converted the digital pins to general purpose, hence the wire placement.

DIY Wokwi

I was a bit irked at the lack of XIAO representation, so I considered making a custom board and add it to Wokwi. I am adding the idea here as I may or may not revisit this depending on the amount of time I have left next week.

C++ Programming

• Setup
  • Go to preferences
  • Install a custom library for the XIAO RP2040.
  • Find microcontroller package in boards manager
  • Run There was no difference in the code due to the same pinout. Searching for the library was a bit of a hassle, though.

C++ Source Code

    void setup() {
        Serial.begin(115200);
        pinMode(26, OUTPUT);
        pinMode(27, OUTPUT);
        pinMode(28, INPUT); 
    }

    void loop() {
      int button = digitalRead(28);

      if (button == HIGH) {
        digitalWrite(26, LOW);
        digitalWrite(27, HIGH);
      } else {
        digitalWrite(26, HIGH);
        digitalWrite(27, LOW);
      }
      delay(50);
    }

MicroPython Programming

• Program
  • Install RP2040 firmware
  • Drag uf2 file to computer folder
  • Run
    
    The process was a bit different, however, I found it easier.

MicroPython Source Code

import time
from machine import Pin
led1 = Pin (26, Pin.OUT)
led2 Pin (27, Pin. OUT)
button = Pin (28, Pin. IN, Pin. PULL_DOWN)

while True:
button_state = button.value()
if button_state == 0:
led1.value(1)
led2.value(0)
else:
led1.value(0)
led2.value(1)
time.sleep(0.1)

Make Buttons

After finishing all that I could do at home, I decided to add one more tweak to my website and put buttons on my homepage.

I used a website that let me copy and paste a screenshot of the main color. It gave me the hexadecimal code, which I could add back. I first tried simply putting in pink, since it worked for mkdocs.yaml, but a different shade appeared. While color descriptions can depend on the library installed, hexadecimal code is universal and foolproof. I also double-checked that I was using the accent color on my website - if I used the background color, the buttons would not be visible without applying a border.

• Create logos

  • Go to Canva
  • Apply hexadecimal code as background
  • Search clipart for relevant images
  • Set image color
  • Set all images to same height without changing the ratio
  • Screenshot individual images and save each as a jpg
    

• Code

  • Copy html button format
  • Modify text
  • Modify links
  • Modify images
    
    I adjusted the height and width of the images to fit most of the button’s height. While most images rendered well, I modified the aspect ratios for the ones that looked slightly too tall or wide. I also noticed that the buttons were all different widths in the preview. I looked at the style section for an explanation. While the center alignment pertained to the text, I was curious about the function of the other line. It originally said display: inline-flex. I searched it up and found that one could enter either that or display: flex. I then used Ctrl+F to find and remove the inline- part. Almost immediately, the button widths uniformly took up the entire row. I much preferred this design for consistency.

Reflection

Group Work

This was not difficult, I already knew how to use a multimeter. I simply re-did a board I already had saved on TinkerCAD and measured voltages.

Positives

Starting on the press fit was very helpful as I can now focus more on creation as opposed to design. I enjoyed making the buttons as well. I found that the CAD aspect was a surprisingly quick start and I’m looking forward to adding some sort of programmable hinge to automate it. Also, the method for adding the grooves was as enjoyable as it was ridiculous. Next week, I will continue this if I have time.

Negatives

It took me a bit longer than I anticipated to re-acclimate to electronics. Electrical Engineering and Pre-Fab saved me here, as I was able to refer to prior knowledge. I should have tried breadboards earlier.

Takeaways

I really ought to bring all the necessary components home to work on the project. While I managed, keeping a list and storage spot would definitely help. Programming the microcontrollers took a while since I had to download the necessary software and re-accustom myself to electronics. Still, the alternating LEDs paid off.

Advice

• Save images as .jpg files. I now use the screenshot snipping tool for individual conversion, but for batch conversion, Irfanview or ImageMagick works. There are several other methods. Also, resize using { width=100% } - one can change the width to their liking.
• For embedding code, I used tabs to indent at first, but looked up an easier method and found one. Make the first line three backticks and the language name, then make the last line three backticks. Also, when I could not find a file, I ran the image in a screenshot through an image to text converter. I would suggest cropping out the line numbers since it includes those.

Files

Arduino

ESP32C3 Blink Switch
RP2040 Blink Switch

Thonny

MicroPython Blink Switch

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Last update: April 5, 2025