Introducing the no-LDO 8Mhz Moteino

From popular demand, there is now a Moteino 8Mhz variant which has the following differences to the regular Moteino:

  • no LDO linear regulator
  • the VIN and 3v3 pins are connected via a 0ohm resistor (including FTDI header VIN)
  • must be powered from 3.6v or less when RFM radio and/or FLASH-MEM are installed onboard, otherwise without radio/external flash the board will work up to 5V
  • 16mhz resonator is still installed but not used with the 8Mhz fuses. This means you can still change the fuses yourself and use it if you’d like, but this will only be safe down to about 3V
  • The fuses are: LOW: 0xD2, HI: 0xDC, EXTENDED: 0xFE
  • even more ultra low power – 2uA less current than the regular Moteino
  • Runs DualOptiboot compiled for 8mhz
  • 57600baud upload programming speed (vs. 115200)
  • you will need to install the latest Moteino definition (v1.3 or newer) in your Arduino IDE Board Manager to gain the new Moteino (8Mhz) target board:

For the latest updates and specs on this board, always check the official Moteino guide.

To program this Moteino the FTDI-Adapter offered in the shop can be modified to pass a safe 3.3V to the 8Mhz LDO-less Moteino – cut the *5V Output Voltage jumper and solder the 3.3V one:

Note that this mod will make the FTDI-Adapter regulate power, but it can only supply about 50mA to the Moteino, if you draw more power, the adapter might drop and reconnect to your computer

Alternatively, you can build a dedicated adapter that takes the 5V from the USB and regulates it to 3.3v, here’s such an example which uses the LDO from the Moteino itself (MCP1703) along with a 1uF and 0.1uF caps, all other connections are passed through and assumed to be 3.3v levels:

You would then use it in between your stock unmodified FTDI-Adapter (or equivalent board, providing 5V VIN power and 3.3V TX/RX/DTR signals), and the no-LDO Moteino which requires 3.3V when radio/flash are present:

These types of Moteinos are ideal for ultra low power coin cell and other micro power powered nodes – power them from 3.6V or less. Of course, when you have such tiny power supplies, you must choose your transceiver carefully, as you likely cannot transmit at full 20dBm power from a tiny coincell. The W/CW 13dBm radios running the auto-power-dial RFM69_ATC library extension would be recommended for running on coin cells or small solar cells.

I can’t wait to see what you guys will make with these!