1. What causes key ghosting and conflicts?
Keyboards typically use a row-column matrix design to save wiring. Pressing three keys at specific matrix intersections can cause current to backfeed along connected paths, causing the microcontroller (MCU) to falsely register an unpressed fourth key (known as Ghosting).
To prevent false inputs, controllers suppress extra signals, causing legitimate key presses to be ignored (known as a Conflict). Anti-ghosting designs optimize matrix wiring for gaming clusters like WASD and Arrow keys.
2. What is the difference between 6KRO and NKRO?
- 6KRO (6-Key Rollover): Restricted by standard USB HID class specifications, limiting packets to 6 standard keys plus modifier keys (Ctrl/Shift). Standard office keyboards use this design.
- NKRO (N-Key Rollover): Hardware features blocking diodes on every switch to prevent signal backfeed. Custom USB descriptors allow infinite simultaneous key presses to be registered.
Keyboard Diagnostics FAQ
Q: Why do PrintScreen or Volume keys only flash briefly during web testing?
Operating systems intercept global hotkeys at the OS driver level to handle system actions, often preventing keyup events from reaching web browsers.
Q: How do I test mechanical switches for key chatter / double-typing?
Corroded mechanical switch contacts or worn leaf springs cause single keypresses to trigger multiple rapid pulses. Monitor CPS metrics or hold durations: normal single presses yielding spikes in CPS or short hold times (<10ms) indicate switch chatter.
