As the current world wide shortage of, well, anything really, spent 30 minutes today tracking down some 220uF Electrolytic capacitors, 5mm pitch that weren’t gold plated, let alone finding a LoRaWAN module and an MCU to suit, I’ve gone back to me roots and updated it a little:
It’s an ATmega4808 28 pin SSOP which is, with a fine tipped soldering iron, feasibly hand-solderable. I’m using a trusty RFM95. The 4808 has 48KB of flash and 6KB of SRAM which is half as much again of flash and three times more than the trusty 328P of Arduino Uno/Nano/Pro Mini fame.
I’ve put the Optiboot boot loader on it, so the Arduino IDE thinks it’s an Arduino and I used the latest MCCI LMIC (v4) that provides v1.0.3 LoRaWAN to test OTAA and the forbidden fruit that is ABP and all is well.
Having turned off some of the junk for Class B but turned up logging to 11 (as I want to explore the MAC commands coming down from v3 a bit more), it took up 26741 bytes of flash (54%) and 1216 bytes SRAM (19%). Plenty of space for sensors and gratuitous text strings. With logging set to 0, it uses 22882 bytes of flash.
So for non-critical applications, I suspect this will be my go-to build for a while until the silicon universe stops ebbing & flowing quite so much.