New April 2022 update!

So far the state of the project:

Finished / pros:

-Cheap and use very few parts

-Rechargeable, the LIC works really nice and it recharges quickly, also no dropping.

-The microcontroller manages the charging  so no need to add a voltage regulator.

-It can be flashed with the usb cable, not standard though,  UPDI needs to be feed intro the D+ signal of USB with a flashing solution like serial to UPDI, I know it isn't standard but it is very convenient and it works really well.

-Now charging works ok using a mosfet controlled by timer A .

-Sleep is implemented.

-Whatchdog is implemented to wake up from sleep every 4 sec.  checks  if device is charging and if the  voltage is below 3.8v and above 2.2v to protect the LIC.

(also resets if hung)

To do / cons:

- Although using the usb to feed the UPDI signal is practical, I don't know if  it would damage a computer if it is connected to it, it shouldn't since the UPDI is pulled up with a 30k resistor but still a concern.

In case of connecting it directly to USB by mistake, using the UPDI adapter to send the signal is ok. 

I tested once and nothing happened  but  doing it repeatedly is another story.

- 4k of flash is a small amount, in my case I have to chop content of the game, someone with more knowledge I am sure can fit more, considering in using a bigger micro????.