This thread is for discussing designing an Ext. breakout module for prototyping and potentially connecting raspberry pi hats.
Some Design Considerations
- Usable as just a PCB (no extra components)
- 2.54mm spacing with through-hole connectors
- Compatible (or at least safe) with raspberry pi hats
I’ve been spending some time getting an iteration worked out. Below are some schematics, layouts, and pin assignments. The main image I’d like to draw attention to is the pin assignment sheet. You’ll notice that this design allows UART, I2C, PCM, SPI, and PWM functions to exist in the same locations. However, with limitations, this leaves several general purpose pins unconnected. Which is why this breakout wouldn’t be guaranteed to work with all hats. However, with with pin functions, 5V, 3V3 and GND all in the same respective locations, this should make hats safe to plug in.
Another requirement to get a hat working on the DevTerm would be remapping pins in the driver /software.
With the 2.54mm spacing, this design would be perfect to solder an IDE ribbon cable, exiting the DevTerm printer door. If you already own a Pi Cobbler, you could plug the cable right into this!
USB, Speakers, and Camera
For compatibility, the 40-pin breakout would not include the camera pins, speaker pins, or USB pins. These are special non-gpio pins. To not completely remove their functionality, I think adding solder pads might be helpful. If this design had a larger scope, it would be possible to re-incorporate the USB ports, camera connector, and speaker pads. But to keep this design low-cost and simple, I think simple pads for these should be fine.
If anyone else is interested in this design, please feel free to jump in on this conversation. At the very least if nobody is interested, this thread will serve as documentation.
Feel free to email me if you are interested in one of these boards! email@example.com
I’ve got a handful of extras All gone for now!.
The next production will be a revision. I’ll also get around to posting the gerber files for anyone who wants to order these PCBs themselves.
Here are the gerber files you can use to order the proto board and the ext board. It’s important to use a PCB thickness of 1mm for the ext breakout! This will ensure it fits in the connector.