DISPLAY :: e-ink (Waveshare 7 inch with IT8951 controller has <1s full refresh rate, also supports partial refresh) SOUND :: 8 OHM / 8W speaker Visaton K50 c
tricky situation: USB charging 5V, LiPo batterias 3.7V, e-ink controller needs 5V, solar panel gives 7V diverse circuits for voltage increase (booster, step-up)