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 using that calibration. These improvements suppress malfunctions caused by baseline shifts — a characteristic issue with magnetic (Hall effect) keyboards.
Background: Why Keys Go Haywire
Magnetic switches read key travel via the Hall sensor’s ADC value (analog value), converting it to a distance in the range 0–255. If the rest baseline (unpressed reference) drifts lower than the actual measured value, a small non-zero distance will appear continuously 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 held down or repeatedly triggered, making the keyboard unresponsive. Previously, startup calibration could only adjust the baseline in one direction, so if the initial value deviated from the actual measurement, the problem persisted.
Solution: Re-establishing 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 a 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 slow, so rapid key presses are never mistaken for baseline drift
- Only the baseline shifts while the travel range is preserved, so dead zones and hysteresis are not increased
As a result, even if the initial value is slightly off, the baseline converges to the correct value shortly after startup, preventing runaway behavior even with shallow actuation settings.
Handling Thermal Drift
During extended use, the keyboard warms up and sensor readings drift overall. Since this is also a “slowly shifting baseline” phenomenon, it is absorbed by the same automatic tracking mechanism described above. Baseline shifts due to temperature changes are corrected continuously during normal use.
Initial Values Based on Switch Configuration
The ReLow60 supports mixing multiple low-profile magnetic switches with different stroke lengths. In v1.8, the startup rest baseline initial value is now set to an appropriate value according to the switch specified in the switch profile of the configurator. This also speeds up initial convergence.
Source Code (GPL-3.0)
The ReLow60 firmware is based on libhmk (GPL-3.0), and the corresponding source is publicly available.
ReLow60 L-HE Firmware (GPL-3.0)
Flashing can be done via the firmware update feature (Web DFU) in ReConf.
ReLow Series Keyboard Configurator