Features

  • Atmega328p @ 16mhz, 3.3v interfacing with the Pi via several GPIO: 2 for the power control (similar to ATXRaspi), 2 for serial (TX, RX), and a pin (pin 22 aka GPIO 25) to RST the atmega328p
  • ability to program it via FTDI header (when Pi is off), from the Pi with avrdude (when the Pi is running), and wirelessly through Moteino’s Wireless Programming capability
  • optional Nokia 5110 84x48px backlit monochrome LCD for anything you want to display, the sample sketch will make use of this, see below for link. This is a great LCD alternative to the 2×20 character LCD I’ve been using before, and cheaper/more common too, and with the great u8glib font support, you can fit really long messages on the screen
  • optional battery backup can be hot plugged in any time if you want to have backup power (standard 1 cell Lithium Polymer, 2Ah+ with embedded protection circuitry recommended). It will also run without a battery as long as USB power is present. While a battery is attached, the charging circuit will charge the battery if external USB power is also present. If external power is lost the battery kicks in to keep your Pi running. The included sample sketch has a voltage threshold that once reached will trigger the Pi to shutdown cleanly
  • Fun fact: a 2000mAh battery will run a typical setup like the one below (Pi B+, wifi dongle, MightyHat + active atmega328p + RFM69HW + LCD) for about 3 hours before it will shutdown the Pi when the battery reaches a low voltage threshold:
  • external power is conveniently provided through the usual micro USB or 2.1mm jack
  • included red/green button makes for a nice power button that will control power to the Pi through the GPIO header and a power path that includes a 5V booster (similar to MightyBoost). The power path to the Pi is latched so that regardless if the atmega328p is reset, the power to the Pi is uninterrupted (as long as USB or battery is plugged in). This makes it possible to reprogram the atmega328p at any time, even directly from the Pi as I will show in a future walkthrough
  • allow RFM69W/HW and LoRa RFM95/96 transceivers to a wide range of low power and long range RF applications
  • the Pi GPIO is doubled to the top of the board where you can solder headers to bring it to the side. The included headers will also protrude and make all pins accessible on top of the PCB already
  • buzzer if you want to get creative with beeps/alerts
  • 2 general purpose buttons (R2+) allow controlling the backlight and view message history:
  • SMA footprint allows soldering SMA connectors for more aesthetic/commercial looking antennas if you mind the usual wire monopole antenna
  • compact design brings all essential ports to one side (where USB/ethernet is) while allowing easy access to all secondary ports (HDMI, audio, SD card access, etc)
  • pinout of GPIO port (connector to Pi):
  • Assembly samples: