epaper_refresh Directory Reference

Directory dependency graph for epaper_refresh:

Directories
	src

Detailed Description

End-to-end example for the e-ink display path (#256). It drives an IT8951-compatible e-paper panel entirely through the display PAL e-ink backend, which layers on the ra8_epaper HAL driver over an injected ra8_io_spi_bus seam. The app itself never names ra8_epaper_*: it paints a canonical RGB565 framebuffer and calls the same six PAL entry points the LCD demo uses, so swapping an LCD panel for e-ink is a one-line iface change.

It performs a full refresh of a checkerboard with the GC16 waveform, then a partial refresh of a small sub-region with the fast A2 waveform, timing both. The SPI bus runs at 10 MHz, under the IT8951's 24 MHz ceiling. The timings are informational only – on silicon a GC16 full refresh is hundreds of milliseconds and an A2 partial tens, while a modelled controller completes instantly – so the verdict never depends on a timing value.

Blocked on

The EK-RA8D2 ships a 7.0-inch parallel-RGB TFT, not e-paper, so there is no IT8951 panel on the bench. On-panel validation needs a real IT8951 carrier (a custom board, or a Waveshare IT8951-AP HAT on the Pmod/SPI header).

ra8_emulator models the IT8951 as an SPI device: it self-frames off the SPI preambles, answers the HRDY ready GPIO, drains GET_DEV_INFO and returns LUT-idle, so the genuine ra8_epaper -> display-PAL -> ra8_io_spi_bus path runs to its verdict with no panel. That model is load-bearing. Run without it and HRDY never asserts, ra8_epaper_init times out, and the app honestly fails – the fake passes only because the modelled controller responds as silicon would.

Pin map (hypothetical carrier)

These are not stock EK-RA8D2 board facts, which is why they live in the app rather than the board layer. They match the pins the emulator's IT8951 model drives; change the k_ep_reset_pin / k_ep_hrdy_pin enums (and the emulator's matching enums) for a different carrier.

Signal	Pin	Direction	Notes
IT8951 /RESET	P4_00	output	pulsed low->high at init
IT8951 HRDY	P4_01	input	panel "ready" – polled before each op
SPI_B bus	SPI_B ch0	–	routed by the carrier
Chip select	SPI_B SSL0	output	hardware CS, not managed by ra8_epaper

Registers

This app touches no MMIO directly: SPI_B sequencing lives in ra8_spi, GPIO in ra8_port_utils, and the IT8951 SPI protocol in ra8_epaper, which carry the register-level citations. The wire protocol follows the IT8951 datasheet rev 0.2 Ch 3.4 "SPI Interface" and Ch 4 "Application Note".