Module17

Module17 - an M17 modem

This project provides a standalone modem that transforms any 9600 baud capable transceiver into an M17 compatible radio. It is based on a STM32F4 microcontroller and is designed to run the OpenRTX firmware. Audio and PTT connectivity is given through a "Kenwood 2 Pin" compatible connector (2.5 and 3.5mm audio jacks) or an OHIS connector (this is not an internet connector).

Several boards of various revisions have been built. The latest one is revision 1.0. This revision went through a complete board re-design, mainly to make it compatible with an ergonomic, extruded aluminum enclosure. It does however remain very similar in principle to the previous revisions. Other changes such as audio input and output improvements were made in this revision.

Revision 1.0 boards can be ordered partially or even fully assembled at PCBWay. Some parts such as the digital potentiometers, the DC-DC converter inductor or the audio power amplifier may not (always) be in stock. Fortunately, they are almost always available through Mouser/Digikey. PCBWay can acquire them through their global sourcing program if you are willing to use it.

Acknowledgments

This project is inspired by David Rowe's SM1000 Codec2 smart microphone.

License

Module 17 hardware is licensed under the CERN Open Hardware License - Weakly Reciprocal

Module 17 is certified by OSHWA under ID BE000019.

More Information

GitHub repository

Features

Radio compatibility list

Flashing Firmware

Quickstart

Enclosure

Revisions

Revision 0.1e

• Replaced digital potentiometers with multiturn ones to improve parts availability
• Moved the TX potentiometer from the op-amp's output to between STM32 and the first op-amp
• Added power-on button
• Fixed misc BOM errors and removed a few unnecessary components from the schematic

Errata for Revision 0.1e:

• R31 has too high value. Add a 2.2k resistor across it (in parallel) to increase the sound volume coming from the speaker. Alternatively, replace R31 with a 1.8k or 2k resistor. Resolved.

Revision 1.0

• Completely redesigned the board, making a design compatible with Hammond enlosures.
• Added connector for HMI board containing buttons and OLED screen.
• Added back digital potentiometers, keeping the footprint for multiturn potentiometers.
• Replaced RC low-pass filter between MCU and speaker power amplifier with an active Sallen-Key (3rd order) topology.
• Added OHIS connector
• Added connector for RTC battery
• Added pull-down resistor on shutdown-line (fixes the board not powering down from OpenRTX menu)