Modbus runs over physical RS485 if you want something more standard.
Is a nice standard, old and proven.
Simple to implement uses simple master initiated command requests and there are plenty of arduino libs to choose from. I’ve developed with it in the past.
The only requirement is having an unique slave address for each slave, that can be done is different ways:
- specify each address on the firmware of each slave
- by jumpers on the slaves boards
- implement custom provisioning mode where the master sends a ‘pair’ request to all slaves and then you have to press a button on all the slaves to establish their own address on the pack
By the way i like your custom solution @scttnlsn !