Scroller: High Resolution Wireless Scroll Wheel

NRF52840 and AMS AS5600 based wireless scroll wheel currently in the MVP state.

As of 2025-05-29 the code portion of this project is on hold while I design the PCBs.

Features

• USB HID High resolution scrolling at 1/120th the typical scroll distance
• Internal scroll accumulation: In regular scrolling mode 120 steps are required per scroll event, In high resolution scrolling mode SCROLLER_STEPS_HI_RES steps are required (default: 1 step)

Planned Features

• Bluetooth HID
• Low power mode for idle state (Device suspend is working, does not support NRF52 periodic waking)

Requirements

This project currently depends on the AS5600 driver being upstreamed in zephyr-drivers/tree/as5600-driver-improvement

Additionally building against a NRF SDK version newer than 3.0.0 is required.

Testing

Information about the device can be viewed (on linux) by running:

# Get the bus and device address
lsusb | grep Scroller

# View the HID descriptor advertised by the device with
usbhid-dump -a [bus]:[address]

This report can be parsed with Frank Zhao's USB Descriptor and Request Parser

# View the stream of reports sent by the device
usbhid-dump -a [bus]:[address] -e stream

# View the kernel level events resulting from the device using evtest and selecting the device
evtest

If the device is registering correctly, evtest should register two different event types. REL_WHEEL is a standard scroll event while REL_WHEEL_HI_RES is 1/120th of the scroll distance of REL_WHEEL. In the kernel lo_res events are emitted only once 120 hi_res events have accumulated. This lets legacy applications still receive lo_res events, while enabling newer applications to scroll in finer steps.

References

• https://www.usb.org/sites/default/files/hut1_5.pdf # Page 40 for resolution multiplier
• https://www.usb.org/sites/default/files/documents/hid1_11.pdf # HID Specification
• http://eleccelerator.com/usbdescreqparser/# # HID Report parser
• https://docs.zephyrproject.org/latest/doxygen/html/group__usb__hid__mk__report__desc.html # Zephyr HID documentation
• qmk/qmk_firmware#17585 # QMK High Resolution scrolling Report
• https://download.microsoft.com/download/b/d/1/bd1f7ef4-7d72-419e-bc5c-9f79ad7bb66e/wheel.docx # Windows High resolution scrolling
• https://patchwork.kernel.org/project/linux-input/patch/20181205004228.10714-5-peter.hutterer@who-t.net/ # Linux kernel high resolution scrolling matching the windows implementation