The core logic behind the firmware implementation of Rapid Trigger (RT) lies in shifting from traditional ”fixed-threshold detection” to ”dynamic directional detection.” Instead of relying on fixed actuation or reset points, it monitors the direction and magnitude of key displacement in real-time.
I. Core Logic: Directional Detection and Dynamic Thresholds
Traditional mechanical keyboards rely on fixed physical contacts; a key must be fully released past the reset point before it can be actuated again. In contrast, the firmware of magnetic-switch keyboards continuously reads the precise position of the switch stem using Hall-effect sensors.
The core firmware logic for Rapid Trigger is as follows: once a key is pressed and reaches the initial actuation point, the subsequent ”reset” determination no longer depends on a fixed position, but rather on ”direction.”
Specifically, once the key is in a pressed state (having passed the user-defined initial actuation point), the firmware continuously compares sensor data between the current frame and the previous frame. As soon as it detects the stem moving upward (i.e., the position value decreases) by a distance exceeding the user-defined ”RT sensitivity” threshold, the firmware immediately marks the key as ”reset.” This means you do not need to lift your finger to a specific physical height; the moment your finger begins to move back, the keyboard recognizes that you intend to release the key.
II. Firmware State Machine
In firmware code (such as ZMK modules or open-source keyboard libraries), RT is typically implemented as a standalone state machine or input processor. It does not directly alter key mappings; instead, it inserts a ”directional filter” layer into the logic governing key actuation and release.
1. Initial Actuation: The key must first move downward and pass the user-defined Primary Actuation Point; at this stage, the firmware outputs a ”press” signal and enters the RT monitoring state.
2. Dynamic Reset: Upon entering the monitoring state, the firmware continuously calculates the derivative of the displacement (i.e., the direction). If the direction is upward (indicating release) and the accumulated upward displacement meets or exceeds the RT sensitivity threshold (e.g., 0.1mm), the firmware immediately outputs a ”release” signal. At this point, the key’s physical position may still be midway through its travel, yet it has already logically reset.
3. Re-triggering: Once the logical reset occurs, the firmware resets the threshold. The finger does not need to return to the top position; simply moving downward again—provided the displacement exceeds the RT sensitivity (or returns to the primary actuation point)—is sufficient to trigger a ”press” signal once more.
III. Integration with Analog Input
This logic is made possible because Hall sensors output continuous analog voltage values, which the firmware converts into digital displacement data with 0.01mm precision via ADC sampling. The firmware executes this detection loop independently for each key, allowing for distinct RT sensitivity settings for different keys—such as WASD and the Space bar—to prevent accidental actuations.
