Determine status of Li-ion charger with Arduino

Im trying to find a way for an Arduino to know when a TP5000 has finished its charge cycle. It has a two color LED (3-pin) that is red while charging & blue when complete. My original plan was to link into the LED’s ‘blue pole’ so the Arduino can see voltage so the blue light must be on and finished charging but two problems have arose:

  • Ive run out of analog pins :frowning:

  • The LED setup is unlike anything Ive seen before. While emitting blue light, the middle (longest) leg isnt
    grounded, its 2.9v and the shortest leg (I assumed the blue pole) is 2.3v. The other mid-length leg is 0v.

Any ideas or other basic solutions?
Bearing in mind, just stopping at 4.2v (since im already measuring voltage) will just eliminate the constant voltage phase of charging so its not ideal

Thanks