Making a pcb board with the Club Puebla shield as a design.
For this week's objective: create a pcb board that integrates LEDs and a push button, all controlled by a XIAO RP2040/RP2350.
As part of our mission, we had to characterize the design rules for our in-house PCB production process (feeds, speeds, tool sizes, etc.). You can read all the intel and documentation gathered by our team by clicking below:
👉 GO TO GROUP ASSIGNMENTTo complete this mission, I gathered the following components from the Fab Lab inventory:
To kick off the blueprinting phase, I recycled the exact same schematic design from Week 06. Since the logic was already perfectly established and verified, I just forged ahead into the PCB editor, routing the traces with a safer 0.8mm width.
The Roland SRM-20 cannot read raw vector lines natively through Mods. It requires high-contrast raster images to calculate the 3D toolpaths. To achieve this, I exported the F.Cu (Front Copper) and Edge.Cuts layers as Gerber files.
Then, I used the gerber2png.fablabkerala.in tool to convert these mathematical vector files into high-resolution (1000 DPI) monochrome PNGs.
Why PNGs? In these images, white represents the material that must remain (the copper traces and pads), while black represents the areas where the endmill will remove material to isolate the circuits. For the outline, the white shape tells the machine the exact boundaries of the board to cut out.
Here are the actual high-contrast PNG files generated by the tool, ready to be processed by Mods. Notice the strict black and white contrast required by the milling machine.
With the high-contrast PNGs ready, I imported them into Mods CE. Mods analyzes the pixels and calculates the exact G-code (in this case, an `.rml` file) that tells the Roland machine where to move on the X, Y, and Z axes.
It is critical to configure the right parameters for each operation depending on the physical endmill used:
| OPERATION | TOOL SIZE | CUT DEPTH | OFFSETS & SPEED |
|---|---|---|---|
| Traces (Isolating Copper) | 1/64 inch (0.4mm) | 0.004 in | Offset: 4 | Speed: 3 mm/s |
| Outline (Cutting Board) | 1/32 inch (0.8mm) | 0.024 in (Max: 0.072) | Offset: 1 | Speed: 3 mm/s |
Before hitting "Cut", physical preparation is mandatory. I secured the FR1 copper board to the sacrificial layer using strong double-sided tape. Then, I installed the 1/64 endmill.
Setting the Z-Axis: This is the most delicate part. I lowered the spindle via VPanel until the endmill was a few millimeters above the copper. Then, I loosened the setscrew, carefully let the tool drop to touch the board surface, pressed it gently down, and tightened the screw. This establishes a perfect Z=0 physical origin.
Inside the VPanel software, I set the X/Y origin where I wanted the cut to start, and registered the Z origin based on the physical calibration described above. I have marked the exact buttons used for this process below.
With all parameters verified and the enclosure closed, the MonoFab SRM-20 went to work. Here is the physical fabrication process captured on video.
The dust settled, and the board emerged perfectly isolated. The next step was washing it and populating it with the electronic components.
After careful soldering and cleaning, the board was fully assembled. Here is the macro shot showing the quality of the solder joints, followed by the physical test to verify the integrity of the circuit and the logic.
With the hardware assembled, it was time to give it a brain. I used the Arduino IDE to program the microcontroller.
The Logic: The code is straightforward but effective. I defined the input for the push button on GPIO 27 (using the internal pull-up logic to ensure a stable reading) and the output for the red SMD LED on GPIO 26. The loop() continuously monitors the button's state. When pressed, the circuit closes to ground (reading LOW), which triggers the microcontroller to send a HIGH signal to the LED, turning it on.
const int ledPin = 26; // SMD Red LED connected to GPIO 26
const int buttonPin = 27; // Push button connected to GPIO 27
void setup() {
// Initialize the LED pin as an output:
pinMode(ledPin, OUTPUT);
// Initialize the pushbutton pin as an input with internal pull-up:
pinMode(buttonPin, INPUT_PULLUP);
}
void loop() {
// Read the state of the pushbutton value:
int buttonState = digitalRead(buttonPin);
// Check if the pushbutton is pressed.
// With a pull-up resistor, the button reads LOW when pressed.
if (buttonState == LOW) {
// Turn LED on:
digitalWrite(ledPin, HIGH);
} else {
// Turn LED off:
digitalWrite(ledPin, LOW);
}
}* Make sure to check the .zip file to confirm it contains the generated PNGs for the milling process as required.
The board has been designed, milled, populated, coded, and successfully tested. Mission accomplished.