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MMDVM_HS Hat for the Raspberry Pi (Zero)

This project provides a Raspberry Pi Hat for the MMDVM_HS Hotspot. It was designed for the Raspberry Pi Zero, but should work on any other Pi with the Hat interface.

First revisions of the board have been built successfully!


The PCB is designed in KiCad and the necessary libraries are included. The supplied Gerber files can be used to order PCBs, for example at Elecrow or DirtyPCBs. The board's dimensions are 65x30mm.

You can order 3 beautiful, purple Revision 1.2 PCBs for $15 at OSHPark!

3D printed Case


Thanks to Toufik, F0DEI we added the sources for a shiny case that you can print with your 3D printer. It may require a little upscaling depending on your printer model. It can carry a Raspberry Pi Zero (W) with MMDVM_HS_Hat (SMA) on top.


Revision 0

This was the first released version that still contains a couple of errors. There is a trace missing between L1 and C1 that needs to be fixed with a small blob of solder or magnet wire. Otherwise the RF connector is not connected to the ADF7021. The GND side of C20 and C22 is not connected to the rest of the board's GND, this needs to be fixed with a little wire to any other GND. CE is connected directly to +3.3V which disallows mode scanning to work. If you just use one mode this is fine, otherwise the connection to the CE pin has to be cut and connected to PC14 on the STM32.

Earlier schematics showed C14 as 1uF. This is wrong and needs to be replaced with 1nF, otherwise the ADF7021 will neither receive nor transmit properly.

With these changes, you can build a fully working MMDVM_HS with the old revision 0 boards

Revision 1

These boards have "Revision 1" written on them. All bugs found in revision 0 are fixed in this version. Apart from that, the STM32's BOOT0 and RESET pins are connected to GPIOs of the Raspberry Pi. This way, flashing should be possible without manually jumpering BOOT0 and triggering a reset.

Component placement did not change between revisions 0 and 1, therefore any stencils for revision 0 should work for revision 1 boards, too.

Revision 1.1

Rewired 3v3 line for Nextion display connector to 5v0. Added SERVICE LED for visual heartbeat. Fixed improper labelling on P25 and YSF LEDs. Due to added LEDs this revision requires a new stencil.

Revision 1.2

This Revision adds support for an optional AN1603-443 ceramic antenna. Insert C27 or C28, depending on what kind of antenna you want to use.

Revision 1.3

The boot jumper was removed and the STlink header moved to its position. This gave space for another 4-pin header allowing to connect I²C OLED displays. No new stencil needed

Revision 1.4

The SVC LED has been rotated and thus aligned to the layout of all other LEDs. The RainSun ceramic antenna has been replaced by a model that can be ordered at Mouser. DC line filtering has been added to 3v3 line.

Revision 1.5

A fith mode LED has been added to the board to show NXDN activity. The two pin headers moved downwards a little. The rev1.4 stencil can be re-used if you manually add solder paste to R19 and D9 afterwards.

Revision 1.6

Inner RX/TX pins of Nextion connector have been swapped. External VCO inductor L6 was added. This is optional for VHF use. D-Star and DMR LEDs were swapped to flash LEDs in proper scan order :).


  • All necessary parts for the Revision 1.1 board can be ordered at Mouser using the following shopping cart
  • All necessary parts for the Revision 1.2 board can be ordered at Mouser using the following shopping cart
  • There is also a light version of revision 1.2 without the reset switch, 2.54mm headers and SMA connector Link
  • The parts for Revision 1.3 board are in this Mouser cart and the light version is here
  • Mouser project for MMDVM_HS_Hat revision 1.4
  • There is another Mouser cart for rev 1.5.
  • And this is the rev1.6 cart and its light version.

Please note that the onboard ceramic antenna is not supplied by Mouser and therefore missing in the carts for revisions up to 1.3.

Either the ADF7021 or the ADF7021-N can be used. Define the proper version in the firmware!

Firmware Installation

Compile and upload manually

For specific details about the firmware installation, check these instructions. The process is similar to the installation on the ZumSpot Pi.

Enable the following settings in Config.h:

#define MMDVM_HS_HAT_REV12
#define ENABLE_ADF7021
#define ADF7021_14_7456
#define STM32_USART1_HOST

Build the firmware:


And finally upload the firmware to the MMDVM_HS_Hat:

sudo make mmdvm_hs_hat

Update within Pi-Star

Andy, MW0MWZ was so kind as to add a script which allows for updating the firmware of the MMDVM_HS_Hat within the running Pi-Star system. It uses the pre-compiled binaries from Andy's (CA6JAU) github repository. The update can be done with:

$ pistar-zumspotflash hs_hat

on the command line.


  • A case for the #MMDVM_HS_Hat can be found at amazon: Case

  • An OLED display also to be found at amazon: Display


This project is released under the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 (CC-BY-NC-SA 3.0, license. You may edit and share it as you like, as long as credit is given and the license is not changed. You can build as many boards for you and your friends as you like and you can even sell it to them to cover your costs, however it is strictly forbidden to turn this into a commercial product! You are not allowed to build and sell these boards for profit!


MMDVM_HS Hat for the Raspberry Pi (Zero)






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