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SPI RA8875

Brent Seidel edited this page Mar 1, 2017 · 1 revision

RA8875 LCD/Touchscreen Controller

This is a bit of a mess. The graphics primitives work. Text works, except that sometimes it mysteriously doesn't work. The chip has many functions and not all of them are implemented. I have only tested the AdaFruit RA8875 breakout board with the 7 inch LCD touchscreen also from AdaFruit. It should work with other sizes.

Usage notes

  1. The RA8875 does not tri-state its MISO pin so it can not share a SPI bus with other devices without some external hardware. It actually is reported to work in some cases but then mysteriously fail. There is some discussion about this in the AdaFruit forums.

  2. The AdaFruit breakout board requires 5V power. The chip itself seems to work at 3V, but the backlight drive circuit needs 5V.

For Further Information

sumtoy has a RA8875 library on github with a bunch of information. If you are coding in C, you may want to use that library. AdaFruit also has a C library for the RA8875.

Definitions and API

The chip has a large number of registers and constants to be defined. Many of the functions are collected into procedures and functions that are hopefully usefull. The definitions and code have not yet stabilized, but I plan to start adding the list here soon.

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