It's funny how decisions you make linger, when you should have bitten the bullet and just changed it.
For years I've lived with a PCB I made with a scrap of copper clad, some really old ferric chloride, some clanky software that limited the size, a inkjet and some veggy oil. It housed a 8 way 1W mux master and the corresponding 8 way IO 1W device. It worked just fine until a few years ago when 1 channel in the 8 way IO reset itself randomly. Then the mux played up. I changed that but the replacement never worked. I'd also had to patch opto couplers around spare IO on the ESP32. It was starting to look a mess
On top of that I had various UPS and regulator designs that had used a toroid which also gave a Vref to AD power meter, then a modified 12V psu to waste minimal energy whilst keeping a lion battery charged weekly.
Finally I'd had enough and bought a MCP23017. That matured for a couple of years then it got to the top of the development pile. That was straight forward. But the UPS function lacked a lot. The battery was now too old, and I could only monitor the battery current through 1W. Enter the INA3221. I'd used one for a quick and dirty UPS for the RPI and I'd found that a single 3.7V lion cell could happily sit on a cheap usb charger, and be boosted back to 5V with really very good efficiency.
Now I have a PCB that I made as a UPS and 4 way IO, but could be cut to provide the remaining 4 IO.
That's better. I also tidied up the wiring, but not that much. Krone blocks are so useful.
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