06: Electronics Production

Goal: Mill, solder, and test custom PCB design
Software: Mods (computes machine routes)
Hardware: Roland SRM20 (milling)
Materials: PCB blanks (copper)
Prior Experience: Some soldering
New Methods: PCB milling

Details:

Printed circuit boards (PCBs) can be made at home
Requires a copper-coated board that can be etched or milled
We will mill ours, cutting away unwanted copper
To start, convert design into milling routes

The milling machine must be told not just where to cut, but what route to take during cutting
Many options for calculating the route
I use Mods, which has a program specifically for Roland SRM20 routes
The routing calculator takes a monochrome PNG (or SVG) as an input
Export PCB design as PNG in EAGLE:

Open the PCB trace file
Select "Display Layers" tab
Hide all layers except the layer you want to calculate a route for
Type "export" in the command line and hit enter
Export as a monochrome .png with at least 300dpi
Note that routes for PCB trace and outline must be calculated separately
So, two separate .png exports!
For me, the PCB features are in layer "Top" and outline is in layer "Dimension"

Convert monochrome PNG to mill route using Mods:

Again, *trace* and *outline* must be done in 2 separate steps!
Always cut traces first to ensure board is immobile
Open Mods and select program: machines > Roland > SRM20 mill > PCB
Import your trace (or outline) .png file
Set PCB default parameters: "mill traces (1/64)" (or "mill outline (1/32)")
Calculate the route in the "Mill Raster 2D" module and review result

Calibrate position of the mill bit:

Use the "WebUSB" module (far right) to connect to the SRM20 via USB
Using "Roland SRM20 Absolute coordinates" module...
Click "move to origin", noting the new location of the bit
Adjust x and y until satisfied
Adjust z until bit is near copper plate surface
Physically lower the bit until touching surface

Re-calculate and send file to machine to cut
Repeat steps for outline after doing trace

Dust and clean PCB of all debris
Check for issues, manually correcting if possible (or fully re-do)
Now, time to solder components

Due to time constraints, I won't be detailing assembly and testing
See embedded programming for parts and embedded programming for basics
This week, I tested an I2C connection with an IMU: BNO-085 dev board from Adafruit
I2C requires four pin connections: SLA, SDA, 3.3V, and ground
As mentioned in electronics design, I matched my 4-pin header to Adafruit's BNO-0xx dev boards
This enables modular plug-and-play testing

Will use same modular approach for testing different buttons/switchs for final project
To test the I2C connection, I used examples from Adafruit's BNO-08x library in Arduino IDE
Initially, it worked! And then, it didn't...
After some troubleshooting, I found that the BNO-085 worked fine with my RP2040 from embedded programming

It's unclear why the BNO-085 stopped working with ESP32-C3 on my custom PCB
Meter readings show that the pins are connected properly
Assuming something mechanical. Will re-build for next time

Files:

[next week]