lowpower_holdpage Directory Reference

Directory dependency graph for lowpower_holdpage:

Directories
	inc
	src

Detailed Description

The #150 power-saving model in its simplest demonstrable form: for a static e-reader page – text shown, waiting for a tap – the Cortex-M85 @ 1 GHz is wasted, so it hands the page to the Cortex-M33 @ 250 MHz and parks. Power saving means dropping to the slow core.

1. The M85 "renders" page 0. A real GLCDC render is M85-heavy and out of scope for this plumbing demo, so a page marker in the shared mailbox at 0x22100000 stands in for the rendered framebuffer.
2. The M85 releases the M33 and parks. ra8_cpu1_release() (HUM Ch 2.9.1) starts the M33; the M85 then sits in a wfi sleep loop, waking only to narrate the M33's heartbeat out of the mailbox.
3. The M33 holds the page. It lights LED1 (P600) as the active-core indicator, polls SW1 (P009) as the page-turn input, and bumps the mailbox heartbeat each loop – all without waking the M85.

The M85 never drives LED1 or the page number after the handoff, so a toggling LED and a climbing heartbeat are honest proof that the M33 is the live core while the M85 sleeps.

Blocked on

What is landed here is the handoff, the slow-core hold loop, the LED indicator and the SW1 page-turn. What no emulator can supply is the real on-bench battery delta of the park (#30), which is the entire point of the exercise. The real GLCDC display-plane and framebuffer handoff to the M33, in place of the page marker, is the other open half of #150.