ReLow60 Firmware v1.8: Automatic Noise Floor Calibration and Thermal Drift Correction
Overview
The ReLow60 L-HE firmware has been updated to v1.8. This release introduces two new features: automatic noise floor (rest baseline) calibration and thermal drift correction based on that calibration. These improvements suppress the misbehavior caused by baseline offset — a problem specific to magnetic (Hall effect) keyboards.
Background: Why Keys Can Go Haywire
Magnetic switches measure key travel by reading ADC values (analog values) from Hall sensors and converting them into a distance in the range 0–255. If the rest baseline (the reference value when the key is unpressed) drifts lower than the actual measured value, the system reports a small non-zero distance even when no key is pressed.
When the actuation point or Rapid Trigger is set extremely shallow, such as 0.01 mm, even a tiny offset can continuously exceed the threshold, causing keys to register as stuck or auto-repeating and rendering input impossible. Previously, the startup calibration could only adjust the baseline in one direction, so if the initial value deviated from the actual measurement, this problem persisted.
Solution: Recalibrating the Baseline During Use
In v1.8, a mechanism has been added that slowly tracks the rest baseline toward the actual measured value, but only while the key is sufficiently released.
- While a key is pressed or in motion, the baseline is frozen and does not interfere with keystrokes in any way
- Tracking is extremely gradual and will not follow rapid key movements
- Only the baseline shifts while the travel range is preserved, so dead zones or hysteresis are not increased
As a result, even if the initial value is slightly off, the baseline converges to the correct reference shortly after startup, preventing runaway behavior even with very shallow actuation settings.
Handling Thermal Drift
When the keyboard warms up during extended use, sensor values drift across the board. Since this is also a phenomenon where “the baseline shifts gradually,” it is absorbed by the same automatic tracking mechanism described above. Baseline offset caused by temperature changes is continuously corrected during normal use.
Initial Values Based on Switch Configuration
The ReLow60 supports mixing multiple low-profile magnetic switches with different travel distances. In v1.8, the initial rest baseline at startup is set to an appropriate value corresponding to the switch specified in the switch profile in the configurator. This also speeds up convergence on the first use.
Source Code (GPL-3.0)
The ReLow60 firmware is based on libhmk (GPL-3.0), and the corresponding source code is publicly available.
ReLow60 L-HE Firmware (GPL-3.0)
Flashing can be performed via the firmware update feature (Web DFU) in ReConf.
ReLow Series Keyboard Configurator