OpenEnergyMonitor Community

Raspberry Pi Model B Rev 2

I am wondering if I should upgrade the SD card running on my Raspberry Pi, but I don’t know if the new versions are compatible with my old Raspberry. Reading the release notes for the latest stable release (24 July 20), it says “Compatible with Raspberry Pi 3, 3B+ & 4”. Does that mean it won’t work with my old Pi?

No, it’s not a complete list, we know it works on Pi Zero W too and I see no reason why it can’t run on an earlier model albeit a bit slow, but if you are not using emoncms heavily/at all then that should pose no issue.

Perhaps that should read “tested with” although I do not know how accurate that is even. It should certainly say “3B, 3B+ & 4B”.

I think the possible “hiccup” maybe the config.txt settings, I know historically that a clock speed was specifically defined, that may not be suitable for slower Pi’s, no idea if it is still done but that should be easy to edit on another machine as it’s just a text file on the boot partition. Likewise with disabling Bluetooth and swapping around the 2 serial ports that the listed models have, the lack of Bluetooth and a single serial port means the blanketed settings may differ, but again that’s done in the config.txt.

As long as you are willing/able to tinker a little you should be able to get it all running on a slower Pi, just avoid trying to do too much that can impact speed like installing nodered or home assistant etc. Go easy and it should be fine, a “B+” has similar resource as a “Zero W” minus the wifi but plus the Ethernet. If it’s a Pi 2B then no problem at all, the first emonPi’s were Pi 2’s.

I confirm that - the present version runs fine - it’s just slow making a year’s worth of graph by way of an example.

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Doh! Just noticed the model is in the title. “Raspberry Pi Model B Rev 2” that will be the older 26pin gpio not the 40pin 1GB B+ but at least rev 2 has 512MB memory not the original 256MB so it should work ok, just slower, like a zero.

If I wanted to use it with an EmonEVSE, for connection to Octopus Agile, with the demand shaper (or whatever it’s called), would it be powerful enough? Or am I looking at needing an upgrade?

Technically, I’m unaware of any reason anything OEM/emon that runs on the latest Pi’s shouldn’t run on anything from a Pi B rev2 onwards (rev 1 might be pushing things too far but you never know) but as I’m not familiar with the EV and demandshaper side of things perhaps @TrystanLea or maybe @borpin could confirm. I suspect if you are prodominantly going to just set it and leave it, then there will be no issue, likewise for the occasional tinker with a smidgen of patience. But if you are going to tinker daily and are in a rush, go for something faster.

IMO there’s something not quite right with constantly buying the latest and greatest for an energy monitor. Not only do the faster bigger specs devices draw more current but the cost of new dwvices offsets the financial gains and environment doesn’t benifiet from replacing tech that is perfectly ok. I thought this project would be championing the reuse of older devices, not leaving them out of current and future development.

So I like that you are concidering the reuse when it is so easy to order new. I would say give it a go, if you don’t like it, buy a new one and move the sdcard over, the changes to accomadate the older Pi (if any) are easy to undo. That’s the beauty of RaspiOS, you can move the image from model to model with minimal fuss and with some simple testing and changes most if not all Pi’s could perhaps be accomadated by one image as the config.txt can be configured to recognise what model it is and apply specific settings.


Just to follow that up with another comment, often the setup and image creation are the hard bit. Often I will get a ad card all set up on a faster Pi then move it to a slower one to tickover and do it’s thing. This is especially useful when heat is an issue, put a Pi 4 in a box you’ll have issue but a Pi B+ will never over heat if simply monitoring and forwarding data and it has plenty of oomph to ssh in now and again to to housekeeping.


I always consider the cost and waste of upgrading unnecessarily, hence the questions. My intentions are to set it up and just leave it uploading data to emoncms in the cloud. Currently I just occasionally ssh to check logs and reboot if it’s got stuck for some reason, but otherwise it’s ticking away merrily all by itself :grin: