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Prevent ghost keys #24

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jackpot51 opened this issue Feb 21, 2020 · 2 comments · Fixed by #40
Closed

Prevent ghost keys #24

jackpot51 opened this issue Feb 21, 2020 · 2 comments · Fixed by #40
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Detect and prevent ghost keypresses
@jackpot51 jackpot51 self-assigned this Feb 24, 2020
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jackpot51 commented Mar 24, 2020 •
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ghosting

In this diagram, SW00, SW01, and SW10 are closed. SW11 is open. Without diodes, current can flow:

  • From C1 through SW01 to R0
  • From R0 through SW00 to C0
  • From C0 through SW10 to R1

This makes it appear as though R1 and C1 are connected, which would make SW11 be detected as closed.

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When a keypress happens, the EC should check if the keypress connects 2 inputs and 2 rows with 3 switches. Any time this happens, the fourth switch would invalidly register at the same time.

@crawfxrd crawfxrd mentioned this issue Mar 31, 2020
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@crawfxrd crawfxrd mentioned this issue Apr 22, 2020
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Ignore key presses that trigger ghost keys system76/ec
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