9. Electronics Production

This week is real fun. I’ve used the Roland MDX-20 here in the lab a few times before I even helped a former co-worker do some 3D engraving once. But that was all four/five years ago and since then I’ve forgotten most of it. Since I’m familiar with the general principles I decided to allocate some of my time to do more programming and test workflows. I’ll be using the Design I did in Assignment 7 Personal goals for this week are:

  • Cut the board I designed already.
  • Program the board using PlatformIO in VSCode(Arduino/C++)
  • Program the board using Arduino IDE (Arduino/C++)
  • Program the board using Thonny (Python)

Hero Shot!

Arduino code done in PlatformIO

Making the board

We have two Roland MDX-20 milling machines here in the lab. We use FR1 stock and use fabmodules to control the machines. I’ve been meaning to test fabmods/modsproject but for this I’m sticking with something I’m at least vaguely familiar with. I did manage to load and look at the modsproject Roland MDX PCB program but it’s almost overwhelming:

ModsProject

I’ll be milling the KiCad files I made in Assignment 7. Electronics Design

Here are the .PNG Files I’m milling:

  • Traces: Traces

  • Edge Cuts: EdgeCuts

I set up fabmodules on my laptop by following the instructions on the fabmodules github page. I did this using WSL.

Traces

Here are the steps I follow to cut the traces:

Steps (Right click > Open image in new tab for larger scale)

  1. Import the traces.png (Make sure it’s the correct scale at 1000DPI)
  2. Select "Roland mill (.rml)
  3. Select "PCB traces(1/64)
  4. Set output>machine to MDX-20
  5. Adjust your x0 y0 and z0. When setting the z0 I move the machine all the way up using the control button on the machine itself, Insert the bit and tighten it before moving the head down close to the material surface. I slowly lower the bit onto the material surface, Making sure not to drop it before tightening the set screw while holding it down against the material so that the screw doesn’t lift the bit.
  6. Double check that you’re using the correct tool, cut depth and that your settings match your design rules.
  7. Hit Calculate to get a preview of your toolpath. Triple check and make sure everything looks correct(I missed an error in this step)
  8. Input the server address. On our local network: 10.50.0.23:12345
  9. Hit Send and it’ll start cutting your toolpath. If you set the z0 to 2mm above you can do a dry-run to make sure your position is correct.

After changing the bit to do the traces I repeated everything except this time instead of PCB Traces (1/64) I use PCB Outline (1/32). Making sure to re-do the z0 and double-checking my x0 and y0.

Here’s the completed board:

BoardComplete

The text came out surprisingly legible. I’ll have to play around with the size and spacing to make it completely millable.

But uh oh! There’s an issue! Notice the vertical trace on the right. Those pads aren’t supposed to be connected. I double checked the Design rules and they had the clearance at 0.4mm. fabmodules had the tool diameter also at 0.4mm, I suppose a minimum distance of 0.45 should resolve this. Good reminder to triple-check your toolpaths.

Pocket knife to the rescue:

BoardBoxCut

After checking all the connections with a multimeter I started soldering.

Soldering

First thing was gathering all the parts I need. I’m using the following components:

Part Name Quantity
SMD Socket Headers 7x1 2x
1k Ohm 1206 Resistor 2x
Red 1206 LED 1x
Blue 1206 LED 1x
Omron Tactile Switch 1x

I didn’t take any pictures/videos while soldering but the process was simple enough. I’ve done plenty of soldering in the past but mostly through-hole. This time was trickier than usual as my hands were extra shaky. Plenty of big blops. Especially on the SMD header pads. Far from my best but everything works so it’ll have to do.

Here’s the board after soldering:

SolderTopDown SolderCloseup

Programming the board.

PlatformIO

I wrote the following program in Arduino through PlatformIO in VSCode. I documented the workflow for PlatformIO in the Electronics Design group assignment. There’s a lot of prerequisites to get the Seeed Xiao RP2040 working in PlatformIO, I go through each of them there.

After adding my code to main.cpp and setting the PlatformIO.ini config correctly I simply hit Ctrl+Shift+B to build then connect the RP2040 in boot mode by holding down the B button (Lower right) while connecting the USB cable. Then I just drag the firmware.uf2 file from .pio/build onto the RP2040 USB device. Success!

Show / Hide Full Program 
#include <Arduino.h>
const int BLUE = D0;   //Defines the pin for the blue LED 
const int RED = D2;   //Defines the pin for the red LED 
const int BUTT_PIN = D4; //defines the pin for the button 


void setup() {
  pinMode(BLUE, OUTPUT);  // Set BLUE LED (Pin 0) as an output
  pinMode(RED, OUTPUT);   // Set RED LED (pin 2) as an output
  pinMode(BUTT_PIN, INPUT_PULLUP); // Set button as input with internal pull-up resistor

  digitalWrite(BLUE, HIGH); // Start with BLUE LED on
  digitalWrite(RED, LOW);  // Start with RED LED off

  Serial.begin(115200); // Initialize serial communication

  Serial.println("RP 2040 Blinky Time"); 
}

// Booleans to track things

boolean WasPushed = false; //Tracks button state
boolean LedState = HIGH; // Tracks LED state (RED uses this, BLU uses this inverted)


// Debounce weirdness (https://docs.arduino.cc/built-in-examples/digital/Debounce/)

const unsigned long DebounceTime = 500; // 500 ms debounce time
unsigned long LastPressTime = 0; //Tracks last time the button state changed

void loop() { //The main loop of the program.

  if (digitalRead(BUTT_PIN) == LOW) { //Checks if the BUTT_PIN input is LOW
    if (!WasPushed && millis() - LastPressTime > DebounceTime){ // If the "WasPushed" is false and the last press was more than 50ms ago
      Serial.println("Pushed!");  //Prints "Pushed!"

    WasPushed = true; //sets "WasPushed" to true. This prevents multiple printings of "Pushed!" while holding down the button.

    unsigned long StartTime = millis(); // Tracks total time 

    if (LastPressTime != 0) { //Checks if last press is more than zero
    unsigned long interval = StartTime - LastPressTime; //Defines "interval" as the difference between StartTime and LastPressTime
    Serial.print("Time since last press: "); //Print in line
    Serial.print(interval); //Print interval in line
    Serial.println(" ms"); //Print "ms". Start new line.
    }


      if (WasPushed) {

        LedState = !LedState;

        // Make Blinky Happen
        digitalWrite(BLUE, LedState); //Sets BLUE to LedState
        digitalWrite(RED, !LedState); //Sets RED to Inverted LedState

      // More print fun. 

        Serial.print("BLUE: ");
        Serial.println(LedState);
        Serial.print("RED: ");
        Serial.println(!LedState);


        LastPressTime = StartTime; //Sets LastPressTime to StartTime, Resetting it for the next loop.



      } 
    }
  }

  if (digitalRead(BUTT_PIN) == HIGH && WasPushed){ //Checks if the button is released and whether "WasPushed" is True. 
    Serial.println("Released!"); //Prints "Released!" 
    WasPushed = false; //Resets "WasPushed" to prepare for next loop.
  }
}


What the program does:

  • Controls two LEDs, One red and one blue.
  • Pressing the button alternates which LED is lit.
  • Prints out the interval between presses.
  • Prints which LED is active.

Arduino IDE

I’ve used the older version of the Arduino IDE before but as I was doing some research I noticed there’s a new version. Installed that and went to set up the Seeed Xiao RP2040. I’m going to use the same program as I used in PlatformIO. Following the instructions on the Seeedstudio wiki. After installing the requirements and selecting the board and port I was able to paste in my code. Verifying passed all checks so I hit Upload and it worked like a charm. Using the Arduino IDE might be better for smaller on the fly code adjustments but I wouldn’t use it for actually writing code.

Thonny

I asked chatGPT to rewrite my Arduino program into Python, Here’s the exact prompt:

Show / Hide Full prompt 
This is a program I wrote for the Seeed Xiao RP2040, Can you rewrite it in Python? I'll use Thonny to program. 

#include <Arduino.h>
const int BLUE = D0;   //Defines the pin for the blue LED 
const int RED = D2;   //Defines the pin for the red LED 
const int BUTT_PIN = D4; //defines the pin for the button 


void setup() {
  pinMode(BLUE, OUTPUT);  // Set BLUE LED (Pin 0) as an output
  pinMode(RED, OUTPUT);   // Set RED LED (pin 2) as an output
  pinMode(BUTT_PIN, INPUT_PULLUP); // Set button as input with internal pull-up resistor

  digitalWrite(BLUE, HIGH); // Start with BLUE LED on
  digitalWrite(RED, LOW);  // Start with RED LED off

  Serial.begin(115200); // Initialize serial communication

  Serial.println("RP 2040 Blinky Time"); 
}

// Booleans to track things

boolean WasPushed = false; //Tracks button state
boolean LedState = HIGH; // Tracks LED state (RED uses this, BLU uses this inverted)


// Debounce weirdness (https://docs.arduino.cc/built-in-examples/digital/Debounce/)

const unsigned long DebounceTime = 500; // 500 ms debounce time
unsigned long LastPressTime = 0; //Tracks last time the button state changed

void loop() { //The main loop of the program.

  if (digitalRead(BUTT_PIN) == LOW) { //Checks if the BUTT_PIN input is LOW
    if (!WasPushed && millis() - LastPressTime > DebounceTime){ // If the "WasPushed" is false and the last press was more than 50ms ago
      Serial.println("Pushed!");  //Prints "Pushed!"

    WasPushed = true; //sets "WasPushed" to true. This prevents multiple printings of "Pushed!" while holding down the button.

    unsigned long StartTime = millis(); // Tracks total time 

    if (LastPressTime != 0) { //Checks if last press is more than zero
    unsigned long interval = StartTime - LastPressTime; //Defines "interval" as the difference between StartTime and LastPressTime
    Serial.print("Time since last press: "); //Print in line
    Serial.print(interval); //Print interval in line
    Serial.println(" ms"); //Print "ms". Start new line.
    }


      if (WasPushed) {

        LedState = !LedState;

        // Make Blinky Happen
        digitalWrite(BLUE, LedState); //Sets BLUE to LedState
        digitalWrite(RED, !LedState); //Sets RED to Inverted LedState

      // More print fun. 

        Serial.print("BLUE: ");
        Serial.println(LedState);
        Serial.print("RED: ");
        Serial.println(!LedState);


        LastPressTime = StartTime; //Sets LastPressTime to StartTime, Resetting it for the next loop.



      } 
    }
  }

  if (digitalRead(BUTT_PIN) == HIGH && WasPushed){ //Checks if the button is released and whether "WasPushed" is True. 
    Serial.println("Released!"); //Prints "Released!" 
    WasPushed = false; //Resets "WasPushed" to prepare for next loop.
  }
}


Here’s the code ChatGPT spat out:

Show / Hide Full prompt 
from machine import Pin
import time

# Define pins
BLUE = Pin(0, Pin.OUT)   # Blue LED
RED = Pin(2, Pin.OUT)    # Red LED
BUTT_PIN = Pin(4, Pin.IN, Pin.PULL_UP)  # Button with internal pull-up

# Initialize LED states
BLUE.value(1)  # Start with BLUE LED on
RED.value(0)   # Start with RED LED off

print("RP2040 Blinky Time")

# Boolean state tracking
WasPushed = False
LedState = True  # True for BLUE ON, RED OFF (inverse logic)

# Debounce timing
DebounceTime = 500  # 500ms debounce time
LastPressTime = 0

while True:
    if BUTT_PIN.value() == 0:  # Button is pressed (LOW)
        if not WasPushed and (time.ticks_ms() - LastPressTime > DebounceTime):
            print("Pushed!")  # Print when button is pressed

            WasPushed = True
            StartTime = time.ticks_ms()

            if LastPressTime != 0:
                interval = time.ticks_diff(StartTime, LastPressTime)
                print(f"Time since last press: {interval} ms")

            # Toggle LED state
            LedState = not LedState
            BLUE.value(LedState)  # Set BLUE to LedState
            RED.value(not LedState)  # Set RED to inverted LedState

            # Print LED states
            print(f"BLUE: {LedState}")
            print(f"RED: {not LedState}")

            LastPressTime = StartTime  # Reset LastPressTime

    if BUTT_PIN.value() == 1 and WasPushed:  # Button released
        print("Released!")  
        WasPushed = False  # Reset for next loop

    time.sleep(0.01)  # Small delay to avoid excessive CPU usage


What it returned seems to make sense. I’ll use it as a starting point for Thonny.

Starting off in Thonny I follow the seeedstudio wiki tutorial. After configuring the RP2040 for MicroPython and successfully getting it to print “Hello World” I tried running the code ChatGPT spat out. It returned absolutely nothing. I glanced through the code and realized the pin assignments were completely wrong. ChatGPT converted the digital C++ pins straight to Python but I needed to change them to the GPIO pin assignments. After that it worked perfectly.

Here’s the section I had to change:

ChatGPT Hallucination:

BLUE = Pin(0, Pin.OUT)   # Blue LED
RED = Pin(2, Pin.OUT)    # Red LED
BUTT_PIN = Pin(4, Pin.IN, Pin.PULL_UP)  # Button with internal pull-up

My Hallucination:

BLUE = Pin(26, Pin.OUT)   # Blue LED
RED = Pin(28, Pin.OUT)    # Red LED
BUTT_PIN = Pin(6, Pin.IN, Pin.PULL_UP)  # Button on GPIO

Here’s a video of the Thonny printouts: