fix(usb): add suspend-timeout fallback for boards without VBUS detect#3375
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paoloantinori wants to merge 1 commit into
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fix(usb): add suspend-timeout fallback for boards without VBUS detect#3375paoloantinori wants to merge 1 commit into
paoloantinori wants to merge 1 commit into
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On boards without VBUS detection (e.g. nRF52840-based Corne-ish Zen), unplugging the USB cable causes the USB peripheral to report USB_DC_SUSPEND instead of USB_DC_DISCONNECTED. ZMK maps SUSPEND to ZMK_USB_CONN_HID, so the endpoint stays on USB and never falls back to BLE. Add CONFIG_ZMK_USB_SUSPEND_DISCONNECT_TIMEOUT_MS (default 0, disabled). When non-zero, a one-shot k_timer is started on USB_DC_SUSPEND; if the bus has not resumed when the timer expires the status is overridden to USB_DC_DISCONNECTED, which triggers the normal endpoint switch to BLE. Enable the workaround for the Corne-ish Zen with a 2-second timeout. Closes zmkfirmware#3374 Tested on Corne-ish Zen hardware: - Plug USB -> display shows USB icon - Unplug USB -> display switches to BT icon within ~2 seconds - Plug USB back in -> display returns to USB icon Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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Issue
Closes #3374
Problem
On boards without VBUS detection (e.g. nRF52840-based Corne-ish Zen), unplugging the USB cable causes the USB peripheral to report
USB_DC_SUSPENDinstead ofUSB_DC_DISCONNECTED. ZMK mapsUSB_DC_SUSPENDtoZMK_USB_CONN_HID, so the endpoint stays on USB and never falls back to BLE. The display keeps showing the USB icon indefinitely.This is related to #841 (USB power-only cable detected as host), which was fixed by PR #2458. That fix addressed power-without-data cables; this one covers cable-removed-entirely.
Solution
Add
CONFIG_ZMK_USB_SUSPEND_DISCONNECT_TIMEOUT_MS(int, default 0 = disabled). When non-zero, a one-shotk_timeris started onUSB_DC_SUSPEND. If noUSB_DC_RESUMEarrives before the timer expires, the status is overridden toUSB_DC_DISCONNECTED, which triggers the normal BLE endpoint fallback.Default is 0 so existing boards are unaffected. Boards that lack VBUS detection can opt in by setting a non-zero timeout in their Kconfig.defconfig.
The Corne-ish Zen enables this with a 2-second timeout.
Testing
Tested on real Corne-ish Zen hardware:
The keyboard config used for testing is at https://github.com/paoloantinori/zmk-config-zen-2
Trade-offs
Without VBUS detection there is no way to distinguish cable unplug from host suspend in software. After the timeout, both cases fall back to BLE. For a wireless keyboard this is reasonable behavior -- the user may want to type on another device while the host is suspended.
Checklist