This is my attempt to make a very small case for N5BOC's excellent Duplex MMDVM modem. In order to do this, I replaced the standard Pi headers with low-profile headers from SamTec, and then designed a case around it.

This build is not for the faint of heart. It involves desoldering and soldering on a $100+ MMDVM modem board, which could result in destroying an expensive bit of kit

See the "How I Designed This" section below for some ideas on how this could be used with a standard height GPIO header

Here's what you need:

• Case parts (I printed in PETG, but I'm sure you could use others)
• MMDVM DUPLEX in Pi Zero Form Factor.
• Raspberry Pi ZeroW
• SAMTEC low-profile headers SLW-120-01-T-D and TLW-120-05-T-D
• 0.96" OLED Display
• 1.75mm t-Glas Filament (Optional) for optical guides
• M2.5x12 (top case) and M2.5x8 (bottom case) screws

The N5BOC duplex comes with a standard female header installed. You'll need to desolder this without destroying the board. I have an electric soldering vacuum gun and even with that it still took some time and patience.

Then you need to install the SAMTEC headers. The male header (TLW-120-05-T-D) has somewhat long leads for soldering (in fact, you might confuse the short pins for the side you should solder.) Make sure you have the right orientation and solder, then clip off the excess leads from the bottom of your Raspberry Pi.

I'll leave it to you to source a 0.96" OLED that works with MMDVMHost. You might need to remove the 4-pin male header.

Since my design re-uses the same holes and screws on the RaspberryPi, you'll need to carefully widen out the holes on the OLED PCB to match the RaspberryPi spacing. I did this with a hand drill, and ruined 2 OLED displays due to carelessness. Do this carefully and make sure not to damage the display.

I used some fine wire-wrap write to make short lengths and solder the display to the pads on the MMDVM board.

I used PETG. I'm sure you can use whatever you prefer.

The bushings are meant to keep the OLED display in place. The smallest pushing will press fit on one of the pegs

If you like, you can ream out the LED holes with a 1.75mm drill bit and then press-fit in some short lengths of t-Glas filament. Cut the t-Glas filament with a sharp razor blade such that you get a nice clean edge on both ends. This makes a nice light guide and bring the LED indicators out to the surface of the case.

Place the end caps into position and then put the bottom case on and force tread the short screws into the end cap holes.

Place the display into the top case and press fit the small bushing onto the small peg of the top case. There is only one small bushing because the pins of the header will interfere with using two of them. This bushing creates a "foot" that prevents the display from being pressed into the MMDVM board. I also put some Kapton tape on the back side of the display to prevent accidental shorts.

Place the larger bushings between the OLED and the MMDVM board and carefully assemble the screws. Force thread the screws into the end caps.

I designed a label that explains what each LED means.

I printed mine on a Laser Printer using "Water Slide" Label paper. You can get it on Amazon. I used the clear variety. They make versions for Laser as well as Ink Jet.

Print your label, and cut it out. Soak the label in clean water for a bit. While under water you should be able to "pinch" the label and get the label to slide off the backing. If you can't get the label to slide off the backing, soak it for a little more. Shake off the water and remove the backing, and then apply the label. (Be careful, the label is very thin, almost like a skin.) Use a microfiber cloth to clean up any remaining water. Be careful, as water and electronics don't mix.

You can find the design in OnShape:

https://cad.onshape.com/documents/b3ab0e110bc0f065ac9f5f74/w/03bd5690e2c317a442b328ad/e/803a72f71f2abb5838f527b0

Note If you don't want to unsolder the standard height GPIO header and use the low-profile SAMTEC ones, the design can probably be easily adapted for a standard PI header. There is a "#BoardToBoard" variable very early up in the feature list. If you change this variable to the proper spacing for a standard GPIO header, the design should update. (Your mileage may vary, as I'm not sure how cleanly I designed all the features within OnShape)