/diy/ - Do It Yourself

>>2774374
Assuming the TP4056 board also has a protection chip on it (e.g. DW01), there should be a place to connect the RP2040's power input after that but before the 12V boost converter. If it doesn't have a protection chip (e.g. pic related) and rather goes straight to the booster, then you'd connect the RP2040 directly to the B+ and B-.

The boost converter itself may have a minimum shutoff voltage between 2.5V and 3.2V, but even if it does your takeoff to the MCU won't. So I'd either write a low-power power-checking routine on the MCU to read the battery voltage via ADC and prevent further battery drain, or by including a conventional protection circuit. The former method is more flexible for thresholds and such, but the standby power draw of the boost converter may be too high without fucking about with it to add a mosfet between the battery and the boost converter. Well, that might not be an issue depending on the boost converter IC.

It would even be an option to use the RP2040 as a battery charge controller and/or as a boost control IC, though I probably wouldn't recommend it. At least it would make the charging and discharging voltage thresholds easily programmable.