Meshtastic 64 – A meshtastic radio for the Commodore 64

Summary

For this project I designed and built a meshtastic radio that plugs directly into the Commodore 64. My goal was to release this at the VCF Midwest show (VCFMW) in Chicago on September 13th and 14th. I barely made it!The finished module plugs into the Commodore 64 User PortThe ideaI had heard some things about meshtastic, but I was no expert. As I looked into it, I learned that it is an open source, decentralized, peer-to-peer, text messaging network designed for long-range mesh communication.This seems to attract people that are either interested in the technology, interested in a decentralized / non-monetized communication system, interested in emergency communication - or any combination. My take was a nerdy 8-bit project to get a 1980s computer on the mesh. I bought some modules off Amazon and started getting results with the Heltec LoRa V3, so that became my platform.PrototypingI then started working on a proof-of-concept version. I wanted to connect using a serial port which the meshtastic supports. I did need to find two IO pins to use and after some investigation settled on pins 45 and 46 of the Heltec.The meshtastic typically communicates using protobuf commands. I spent some time untangling these, but soon shifted to the SERIAL>MODE>TEXT_MODE setting. This focuses on simply sending and receiving text through the meshtastic primary channel. Soon I had a proto board which was sized to fit in a reproduction Commodore 64 cartridge shell. The shell's recessed label area is untextured and made a perfect lens over the little display.Coding on the Commodore 64I worked on a program for the Commodore 64. I chose to write the program in BASIC because it was quick for me to develop with, very retro, and the speed needed for text input and printing to the screen was acceptable. I did much of the programming on an actual Commodore 64, but transitioned to CBM Program Studio on my laptop while traveling.First Programming SetupInterface PCB designThen I laid out the PCB. I ...