Wednesday, November 23, 2022

New Radio Mini Node

There was a little happening on development side of OHS lately. The gateway line 2.0.x
works very stable. No issues found in software or hardware. Arduino based nodes are also reliable. Basically it works as intended, "install and forget". 

But the word is changing and so are the evolution of chips. ATmegas, and also other components are becoming hard to get, and the prices of ATmega tripled. While using STM32 Cortex M4 chips for gateway, I realised they are great replacements, allowing us to do stuff not imaginable on AVR. For example STM32duino, I've been watching the progress of it for long time, and also, I have some blue/black pills on hand. So I decided to give them a try also on OHS environment. I've created a STM32 Radio Node Mini, which render is shown on picture. 

It is 50*24mm board with STM32F103C6T6 Cortex M3 running up to 72MHz with 64KB of flash and 20KB SRAM. Basically well known bluepill. It's meant to be used as radio node, so on back there is place to mount RFM69 or LoRa RFM95/96 module. It has a u.UL connector or place for wire antenna. Board has also 3.7V Li-ion battery charger, and battery measurement resistor divider connected to MCU ADC pin. It is programmable directly via USB port, or it has SWD. There is also RTC quartz crystal which allows indefinite sleeps instead of ATmegas maximum 8 seconds. It has LED on PC13, and also on top a place to mount various temperature/humidity sensors like HTU21D. PCB comes with mounting holes to fit in various places.

Currently I'm having those fabricated, and as soon as I have some of them tested and I'm ready with proper software, I will report more.