(1 customer review)

SKU: MDMRC24B Category:

Important! This product is now discontinued. Please have a look at OpenModem instead. It offers a much more powerful feature-set, is easier to use, and is the platform I will be developing in the future. The information on this page is for reference purposes only.

One MicroModem, hand-assembled, tested and flashed with the firmware of your choice. By default, I will ship it with MicroAPRS KISS firmware. If you want something else, let me know in the order comments!
You can choose whether or not you want the modem with pin connector sockets. They come unsoldered to the board, so you can just solder on the ones you need. If you want to solder wires directly to the board, the version without connectors is great!

For user manual, firmware downloads, schematics and other resources, go to this page.


  • ATmega328p @ 16MHz (2KB RAM / 32KB flash)
  • Powered from USB or external regulated 5V source
  • 51mA idle power consumption
  • Operating range: -20°C to 70°C (non-condensing)
  • Great demodulator performance, decodes ~900 packets from the TNC Test CD
  • Modulated analog output level adjustable from approximately 15mV to 1.5V peak-to-peak
  • Minimum analog input level for good decode is about 100mV peak-to-peak
  • ADC running on 3.3v reference
  • Arduino compatible (You can program the board from the Arduino IDE, over USB)
  • Connectors:
    • USB Mini-B (USB-powered)
    • Audio out (modulator output)
    • Audio in (demodulator input)
    • Ground x2
    • VCC (5V) x2
    • 3.3V output (Max current 50mA)
    • PTT_V+ (for Kenwood style PTT)
    • PTT (logic level PTT signal)
    • UART – RX / TX (Arduino pins D0 & D1)
    • I2C – SCL / SDA (Arduino pins A4 & A5)
    • SPI
      • SCLK (Arduino pin D11)
      • MISO (Arduino pin D12)
      • MOSI (Arduino pin D13)
      • DTR (Reset pin)
  • Flexible firmware support, use one of the provided firmwares, or create your own!
      • Choose this if you want to use the modem as a KISS TNC, or with any kind of APRS software
    • APRS SimpleSerial
      • Choose this if you want to control the modem over a serial connection with a simple command-driven interface
    • MicroModemGP (general purpose, SLIP support)
      • Choose this if you want to make custom applications with the modem, or want to use it for IP traffic
  • Arduino APRS library available, create your own APRS firmwares easily!
  • All firmwares are Open Source, and available on GitHub
  • Hardware design is Open Source, and available on GitHub

To easily program this board from the Arduino IDE, have a look at this page.

1 review for MicroModem

  1. KJ4HDR/I8

    Attached to an USB port of my Linux box (comes up as a “/dev/ttyUSB*” serial port), currently using it to monitor APRS traffic and publish a daily page summary:
    Sources available here:
    (if you only want to decode APRS packet fields, you need “” only).

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