MicroModemGP

MicroModemGP is a general purpose firmware for MicroModem.

It supports both KISS mode serial connections, and direct serial connection without framing for easy communication with anything with a serial port.

You can buy a complete modem from my shop, or you can build one yourself pretty easily. Take a look at the documentation in the MicroModem repository for information and getting started guides!

Some features

• Easily send and receive packets over mostly any radio
• Full modulation and demodulation in software
• Flexibility in how received packets are output over serial connection
• Can run with open squelch
• Supports KISS mode for use with programs on a host computer
• 12,8 Hamming-code forward error correction and 12-byte interleaving
• CRC checksum on packets ensure data integrity
• Supports packets with up to 792 bytes of data

KISS mode

When the modem is running in KISS mode, there's really not much more to it than connecting the modem to a computer, opening whatever program you want to use with it, and off you go.

Direct serial connection

If you want to use the SimpleSerial protocol, here's how to control the APRS modem over a serial connection. The modem accepts a variety of commands for setting options and sending packets. Generally a command starts with one or more characters defining the command, and then whatever data is needed to set the options for that command. Here's a list of the currently available commands:

Serial connection settings

To connect to the modem use 9600 baud, 8N1 serial. By default, the firmware uses time-sensitive input, which means that it will buffer serial data as it comes in, and when it has received no data for a few milliseconds, it will start interpreting whatever it has received. This means you need to set your serial terminal program to not send data for every keystroke, but only on new-line, or pressing send or whatever. You can also compile the firmware for KISS mode serial connection, if you have a host program using KISS.

The project has been implemented in your normal C with makefile style, and uses AVR Libc. The firmware is compatible with Arduino-based products, although it was not written in the Arduino IDE.

Visit my site for questions, comments and other details.