Bufferless e-paper
Introduction E-paper displays come in many forms, both in terms of size and how the pixels are controlled. For this article I'm going to focus on the less expensive serial interface type (SPI bus) which have a built-in controller (COG = controller on glass) and come with their own framebuffer memory. Since the panel itself has the necessary memory to hold all of the pixels it displays, it's possible to do quite a lot without needing any RAM on the MCU side. For those familiar with OLED displays like the popular 128x64 SSD1306, the memory of these e-paper panels can be managed in a similar way. Bufferless Limitations Working without a local copy of the graphics presents some challenges. You can define a memory window (a smaller rectangle of the display) of any number of bytes (not pixels). This means that in one direction, you only have access to 8 pixels at a time, since the memory planes are each 1-bit per pixel, packed 8 to a byte. Some e-paper controllers allow you to read t