I’ve been doing some LoRa projects lately in order to learn as much as I can about this exciting new radio technology (see this LoRa mesh networking project and this LoRa weather station). ATmega328-based Moteino modules work great for a lot of projects, but I wanted a LoRa node with more processing power, more memory, and an onboard GPS receiver. The ATmega328 is just too constrained with memory — I’ve outgrown it (ed: so have we all). I really wanted a LoRa board with an ARM Cortex microcontroller like the SAMD21. This is the microcontroller used on the Arduino Zero. So, my ideal board is a SAMD21 with LoRa radio module and GPS receiver, all programmable with the Arduino IDE.
But, where is such a board? I could not find one so I decided to design and make one myself.
The repo has example code for the SAMD21-based LoRa GPS development board described here. This board can be programmed with Arduino as an Arduino Zero. The board uses a SAMD21E18A microcontroller which has fewer pins than the ‘G’ variant of this chip used on the Arduino Zero, and the Arduino Zero pins used for SPI are not present in this package. The way to get around this is to either define a new Arduino core for this chip variant, or to define a new SPI interface on pins that we do have. I want to program this chip as an ordinary Arduino Zero, so I defined a new SPI interface called SPI1 according to this Adafruit tutorial.
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