E-Paper hat rev2.3

[ltwin8]

I have read a bit about the support of the driver hardware, the people reporting issues with the rev2.3 hardware could try to "re-update" their driver hardware. the inductor (old 68uH new 10uH) seems not to be the issue but the MOSFET Q1 seems to be at fault here.

https://files.waveshare.com/upload/8/8e/E-Paper_Driver_HAT.pdf (2.3) https://files.waveshare.com/upload/8/87/E-Paper-Driver-HAT-Schematic.pdf (2.2)

The transistor Q1 is responsible for creating the driver voltages, those ones are buffered in a 4.7uF MLCC, during dithering this "reservoir" seems to run dry and the DCDC can not keep up "refilling" it

the setting of RSEL to 470mR should allow higher current (after all its the sense shunt) but the transistor Q1 has a way to high Rds_on (around 3R) compared to the old one (around 0.2R) so i recommend to solder a transistor of this type "SI1308EDL-T1-GE3" or simmilar.

important is the following: Vds >= 30V Vgs_th <= 2V Rds_on <= 0.25R at 2.5V-3V Vgs low total gate charge, less than 2.5nC

this transistor is likely the one build into the old board: https://www.mouser.de/ProductDetail/Vishay-Semiconductors/SI1308EDL-T1-GE3?qs=bX1%252BNvsK%2FBramh9tgpOaEw%3D%3D

if you search for alternaives filter the results at your supplier of choice with the above given values and there you go... to finish the decision open the datasheet, search pinout and compare to datasheet of SI1308EDL-T1-GE3 (available at the link above)

To those not very experienced with soldering or dont have rework equipment: the old MOSFETon the board can get destroyed, either remove its plastic with a nail clipper or simmilar, than heat the 3 pads simultaniously or put a blob of solder on each of the 3 pads and do round robin heating. to solder in the new one should be easy, tin the leads, put it with tweezers in place, shotrt heat to each pad should be sufficient for reflowing

to make the effort in reviving the "new and better (sure...)" driver hat (2.3) can have some advantage because it does after all provide a layer of additional ESD protection for the screen.

if helpful maybe add this guide to the readme, as i think this "hack" is not so difficult to perform