01-15-2020, 06:16 PM
(This post was last modified: 01-15-2020, 06:23 PM by resistanceisfutile.)
(01-15-2020, 06:03 PM)C_Elegans Wrote: I have a logic analyzer fast enough to capture 400kHz i2c, but I do have a question that I'd want answered before hooking my pbp up.
1. How do I use the laptop with the cover removed safely? The wiki mentions possible structural damage to the computer if you open it while the bottom cover is off. To capture the firmware I could leave the laptop closed and do the update via SSH or something, but in order to capture the i2c traffic from the trackpad itself, I'd need to have it open with the trackpad available while the cover is off.
If you haven't yet dissassembled it, there are some gotchas I don't think were mentioned. Namely the two speakers. The bottom shell is SHARP, so be mindful. The speakers have an adhesive and sometimes stick to the bottom shell. They're connected by very thin wires. When you're pulling the bottom shell off, do so very slowly and check to see if either of the speakers are sticking to the bottom shell. You'll need to carefully unstick them before fully removing the shell.
After dissassembly, the first thing I did was unhooked the battery. There is a yellow sticker with an important note about the bypass cable. Each end of the bypass cable is stuck to the internal chassis with some black adhesive near/under the yellow sticker. AFTER AND ONLY AFTER you have disconnected and/or removed the battery, connect the bypass cable. DO NOT forget to unhook the bypass cable before hooking the battery back up and re-assembling!!!
I then soldered my probe wires to the touchpad's test points.
Then, while only placing pressure with my fingers as close to the hinges as possible, I very carefully and slowly opened the hinges and turned the laptop over to it's normal operating position - with the probe wires sticking out in front of the unit.
After reassembly, the hinges appear fine. No apparent damage. Oh - don't forget about the two plastic retainer clips!
(01-15-2020, 06:10 PM)Der Geist der Maschine Wrote:(01-15-2020, 05:17 PM)resistanceisfutile Wrote: * A dump of sniffed i2c traffic during a firmware update of the touchpad.
* A dump of sniffed i2c traffic while using the touchpad, with correlation to what was happening on the touch pad (tapping, two fingers, scroll, pressing the buttons, etc.)
Can't you instrument the kernel i2c driver to log what it sends out?
99% certain this i2c bus is not visible to the SoC, so the kernel won't see anything.
