APRS Tracker Known as WhereAVR

The Automatic Packet reporting System (APRS) tracker WhereAVR is a low-cost, low-power, lightweight/small device which is capable of decoding ax.25 packets while featuring a full complement of analog and digital I/O.

By attaching directly to the speaker and microphone jacks of a handheld radio, the WhereAVR allows the reception of remote commands without the need for a real TNC. The TNC is a device used for GPS tracking and telemetry as well as attempting to initiate a cut-down commands. APRS refers to an amateur radio based system for real-time tactical digital communications of information of immediate value in the local area by collecting all data and ingesting it into the APRS internet system before distributing the data globally.

The board was designed around Atmel ATmega8 which can be programmed in-circuit. Along with the microprocessor are some active and passive components. Also included are some LEDs for transmit and DCD detect indication, and converter for the GPS receiver. In order to scale inputs to send into the analog-to-digital converter, a section was set aside for loading voltage dividers. The GPS receiver level converter uses a single transistor as an inverter driven with GPS input.

Rest of the project