1.54 double-layer plug-in board - slave board

• Thanks to Lichuang user @1174247739lc for providing ideas!
• By adding the lower layer, functions such as ink screen access control keychain, portable small calendar, photo decoration, etc. can be realized.
• The motherboard can use esp8266, msp430, stm, etc. All can be replaced to expand playability .
• 2.00mm pins are used instead of the commonly used 2.54mm, because 2.00mm is shorter and takes up less space.
• The fpc socket is compatible with 34pin and 24pin , and is positioned through silk screen
• The screen switching function is retained . It is a toggle switch on the micro-ski board. Some boards directly delete the changing function. This board uses a compromise method and uses a 0 ohm resistor instead of the switch. After all, screen switching is not commonly used, but it cannot be left out. Not www
• The 3-wire SPI and 4-wire SPI switching is also retained , and is switched with a 0 ohm resistor.
• Thanks to Weixue wiki.

I'll try to answer all your questions as best I can, thanks for the comments!