TNC-Pi is a unique variation of TNC-X made specifically to connect directly with the Raspberry Pi device. It has the option to connect to the Pi through either the Pi’s serial port or the I2C protocol. In this scenario, one Raspberry Pi can accommodate several TNC-Pi devices simultaneously by assigning each TNC-Pi a distinct I2C address.
The TNC-Pi firmware was created using the original TNC-X open source code by John Hansen, W2FS, with modifications from John Wiseman, G8BPQ to add support for the I2C protocol in addition to the standard serial port connection.
TNC-Pi has a wide range of possible uses. In this setup, the APRS software Xastir is being used on a Raspberry Pi to operate a TNC-Pi through a serial link. This arrangement provides most of the same features as a D700/Avmap setup, but at a much lower cost.
Development of a Linux version of the WinLink program Paclink is currently in progress. Picture the potential reduction in size of your WinLink station by constructing it with a Raspberry Pi/TNC-Pi duo.
Imagine running a pair of TNC-Pi with a single Raspberry Pi to create a dual-frequency digipeater. G8BPQ has created a new version of his venerable BPQ multi-port packet program that will support this.
TNC-Pi is a fun, easy to build kit. All parts are through-hole; there’s absolutely no surface mount soldering involved. You can view a copy of the manual here.
Circuit diagram
For more detail: TNC-X for Raspberry Pi (Packet radio) AX25
