I’m working on an embedded software-defined radio for sending PSK31 telemetry data that can run in the BeagleBone Black PRU (or perhaps repurposing the LCD interface) as well as smaller devices like the Teensy 3.1 with an embedded Digital-to-analog converter. Preliminary source is available from github….
BeagleBone Black PRU
Using a BeagleBone Black instead of the teensy opens up more useful spectrum. The DAC on the Teensy is limited to mostly audio frequency ranges, but the PRU can easily generate a smooth 2.5 MHz carrier. A simple R2R DAC isn’t the cleanest , but generates acceptable signal that was capable of being received a few meters from the IC-7000 without any amplifier.