From 3d60be5bfb7f0e87065795ef723135bf0504748a Mon Sep 17 00:00:00 2001 From: Daniel Schaefer Date: Tue, 19 Nov 2024 14:34:09 +0800 Subject: [PATCH] README: Document touchpad protocol Closes #10 Signed-off-by: Daniel Schaefer --- README.md | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/README.md b/README.md index 860cef0..5b9470d 100644 --- a/README.md +++ b/README.md @@ -113,3 +113,13 @@ to ground or other signals when sliding in if the solder mask is scraped away. ![image](https://github.com/FrameworkComputer/InputModules/assets/28994301/e8d65dad-9d55-4d5a-b97c-3ccbd33e1fb6) +### Touchpad I2C Protocol + +The I2C bus from the touchpad is connected to the CPU for HID over I2C and +implements the [Precision Touchpad Protocol](https://learn.microsoft.com/en-us/windows-hardware/design/component-guidelines/touchpad-protocol-implementation). + +It's also connected to the EC. This is used when booting without a touchpad. +If the Windows driver tries to connect to an I2C device but finds it does not respond, it will disable that device. +So we make the [EC pretend](https://github.com/FrameworkComputer/EmbeddedController/commit/9d49389919c36e44e451514b8278b9eb7ee6ed1e) +to be the touchpad and send the same HID report descriptor as the touchpad would. +