Practical I/O triage for laptop keyboards and touchpads (original NLCRC English).
Separate domains
- Matrix keyboard via EC vs USB HID keyboard modules.
- Touchpad over I2C/PS2/USB depending on OEM — schematic tells you which.
After liquid or cable work
- Reseat FPC with correct orientation; look for torn traces at the connector stiffener.
- Check EC VCC and pull-ups on I2C lines before replacing the whole EC.
- External USB keyboard working while internal is dead → lean cable/matrix/EC KSO-KSI, not “whole board dead”.
Do not forget
- Keyboard backlight rails are separate from key scan.
- Some boards need a matching EC build after top-case swaps.
When asking: board PN, photo of the FPC connector, whether USB keyboard works in BIOS, and any spill history.
Peripherals & I/O
Keyboard / touchpad / FPC: dead input after a spill or cable swap
Board: Keyboard FPC · 26 views · Solved
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