Flashing MMDVM on an STM32 Nucleo using OS X

As you may already know from a previous post, I've been experimenting with MMDVM (Multi Mode Digital Voice Modem), software that can be used to operate a DMR radio hotspot or repeater. Historically I've been using a DVMega hotspot 'shield' on a Raspberry Pi, however I'm now taking it up a notch and building a 'proof of concept' DMR repeater.

The MMDVM Modem is made up of several components-

• The interface board - Interfaces with the radios and performs the necessary filtering and amplification of the Tx and Rx Signals
• The Modem - an embedded microcontroller for doing the analog to digital and digital to analog conversion and sampling.
• The Host - usually a Raspberry Pi. Manages the modem and performs actions such as relaying DMR frames to the network.

The MMDVM software will run on several different platforms including the Arduino Due, the Teensy's, and the STM32 Nucleo. The DUE's are EoL, and the Teensy's are expensive, which left the STM32 as the logical option.

This guide is aimed at flashing the STM32 Nucleo board (STM32F446RE) for use with one of F0DEI's highly recommended MMDVM boards using MAC OS X. If you're using another MMDVM board, you may need to tweak the Config.h file accordingly.

I've not used an STM32 Nucleo before, so I had to do some research to figure out how to flash it. I've written up my findings below.

If you're using Windows I recommend F5UII's blog post here

The STM32 Nucleo

F0DEI's MMDVM Board

I tested this on 03/05/2020 and it worked as expected!

Adding a Nextion display to a MMDVMHost Hotspot

In a recent post I ran through setting a Raspberry Pi as a DMR hotspot using a DVMega and MMDVMHost.

MMDVMHost natively supports various displays including various TFT's manufactured by Nextion, 128x64 OLED screens commonly seen in Arduino projects, and HD44780 based LCD displays.

I wanted something colourful but still compact, so I went with a 2.4" Nextion screen available on Ebay here for around £12.50.  Shipping from China took just over 2 weeks which is satisfactory.

I also required a USB to Serial adapter to drive the display, as the Raspberry Pi's built in serial port was already being used to control the DVMega. This was purchased from Ebay here for £2.70.

The end result (Enclosure coming soon!)

For the instructions, click 'read more'

Using a Raspberry Pi 3 as a WiFi Client and Access Point simultaneously.

The Raspberry Pi 3 has a built in Wifi chip, which supports client mode (Connecting to a network) and access point mode (Hosting the network other clients connect to). It can also do these simultaneously, allowing the Pi to connect to a network via Wifi (Or Ethernet, or 3G) and share its connection with other devices.

This can be useful in the case of public Wifi that requires some kind of login or registration. As I run my Pi 'headless', I can't authenticate via the Pi itself, but I can now connect to the Pi's access point and go through the registration process. It also means on networks that block client-to-client communication, a device can still access services hosted on the Pi and still access the internet.

Please find the instructions below.