Driver for IT8951 E-Paper display

This crate is mainly developed for the waveshare 7.8" epaper display using spi: https://www.waveshare.com/wiki/7.8inch_e-Paper_HAT The driver uses the embedded_hal traits as hardware abstraction layer. This driver can be used with the embedded graphics trait, currently only supporing Gray4 (16bit grayscale).

Details

• IT8951 has a image load engine which can convert pixel data before storing it in the local frame buffer.
• It is possible to read and write the memory directly without using the image load engine
• Important Data must be always aligned to 16bit words!
• The crates uses the alloc feature to allocate memory on the heap:

  • Firmware and LUT version string read from the controller

  • Staging buffers to write pixel to the controller. The buffers are allocated as needed, but only one buffer at a time and with up to 1kByte of size.

  • When reading controller memory a staging buffer with the size of of the requested data is created.

TODOs

• Support Gray2 and Gray8 with embedded-graphics
• Support display engine fill area
• Support display engine 1 bit per pixel mode
• Support static buffer allocations

Changelog

0.4.0

• Public API new expects a Config parameter to set timeout and buffer size. Default is implemented with timeouts of 15s and buffer size is 1024 Bytes.
• Buffer data type changed from u16 to u8
  • Public API: load_image_area, load_image, and memory_burst_write functions are now using u8 as buffer type
  • Memory usage is reduced by half (1kByte max. instead of 2kByte)
• Behavior Calling init no longer clears the eink display. Instead call reset directly.