How to Make a Raspberry Pi Compute Module 4 Carrier Board in KiCad - Part 2 | Digi-Key Electronics

Raspberry Pi released the Compute Module 4 (CM4) in October, which is a single board computer with all of the processing power of the Raspberry Pi 4, but in a tiny form factor! It removes many of the connectors (USB, HDMI, etc.), as the intention is for you to add your own with a custom board and enclosure.

The CM4 is not intended to be a desktop replacement (like the RPi 4) but rather to be used in industrial or professional cases where you might need an SBC embedded in, say, a robot.

In this series, we’ll show you how to create your own, custom Raspberry Pi CM4 carrier board with KiCad!

In this second episode, we continue where we left off by setting our board parameters to those given by our PCB manufacturer (I use OSH Park in this case - https://oshpark.com/).

Then, we arrange the footprints around the sides of the CM4, as we cannot place tall components under the CM4.

From there, we start the routing process with the USB D+ and D- lines, as they are the most vulnerable to cross-talk, EMI, reflections, etc. We use the built-in KiCad calculator to determine the width and separation of the differential pair and use those parameters to create traces that should be good enough for USB data transmission.

After, we route the power lines and then the rest of the data lines. We finish by adding ground pours to the top and bottom layers. We add some vias to connect the ground pours and tidy up the layout. By running the DRC tool, we can see if there are any errors from unconnected nets or spacing violations.

When we’re sure that the layout is good, we move silkscreen around (yes, I know I forgot to add GPIO pin names...oh well), and we generate gerber files and a bill of materials (BOM). We then ship these files off to our manufacturer and order parts from Digi-Key!

Note that I have not tested the board by the time this video was posted. As a result, I do not know if it works. Perhaps on a later episode, I can show it working (and if I ran into any errors!).

The GitHub repo for the Base Carrier shown in this video can be found here: https://github.com/ShawnHymel/rpi-cm4...

Product Links:
https://www.digikey.com/en/products/f...

Related Videos:
Introduction to KiCad series:    • An Intro to KiCad – Part 1: How PCBs ...  

Related Project Link:
Creating a Raspberry Pi Compute Module 4 (CM4) Carrier Board in KiCad - https://www.digikey.com/en/maker/proj...

How to Route Differential Pairs in KiCad (for USB) - https://www.digikey.com/en/maker/proj...

Related Article Links:
Beginner’s Guide to KiCad - https://www.digikey.com/en/maker/proj...