micro.modem.nano.v0a1

2 layer board of 0.67x1.67 inches (17x42mm). $5.60 for three.

Atmega328p-based 1200 Baud AFSK radio modem

MicroModem MicroModem is an open-source implementation of a 1200-baud AFSK / Bell 202 modem on the popular ATmega328p microprocessor. MicroModem can be used for things like ham radio APRS, AX.25, TCP/IP over SLIP, experimentation with mesh-networks, long-range wireless communication with sensors (Or friends! Or strangers!). It basically comes in two flavors: Prebuilt or DIY.

It is simple enough that, if you have some basic electronics experience, you can understand and build it yourself with a few components and an Arduino. You can also get a more advanced and prebuilt, fully tested MicroModem directly from original designer. He manufacture them personally, to the highest quality. (link/store at his site)

Please note that the resources listed here for building your own MicroModem are for an earlier, more simple version, than the one he currently offers for sale. While the two modems are functionally identical, the version he offers for sale has some technical refinements, and is implemented as an integrated board with MCU, USB and everything on one board, measuring only 3×5 cm. The DIY version is a board with all the external circuitry needed for turning a standard Arduino (or compatible like Microduino) into a MicroModem!

This is my adaptation of the MicroModem DIY, it is upsized to the footprint of the arduino nano (I got one for $2.99 vs the $18 it would take for the MicroModem Core USB), this is a conversion and should be a 1-1 pinout match for Marks MicroModem (so his pre-compiled hex files should work with no modification or need for re-compile) but for the MUCH cheaper arduino nano.

Correction for missing trace, and for the used arduino nano library to correct reversal of analog pins.

-untested- at the moment