Rvnash has developed code to output the required tones to transmit APRS (Automatic Packet Reporting System) packets on the Teensy 3.1’s DAC pin, which is then modulated to the required frequency using a Radiometrix HX1 transmitter module.

APRS is a radio-based system for relaying various data of interest to users in the broadcasting region.

As is often the case on the PJRC forums, various other members were inspired by the project, including Malaysian ham enthusiast Stanley, who used it to upgrade their own open-source APRS Tracker, SVTrackR. rvnash’s code, as well as Stanley’s project, are available on GitHub.