Fix modifier keys for BLE keyboards without report IDs - #366
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The Bluetooth notify callback unconditionally prepended the report ID byte to report data before passing it to handle_received_report(). For devices whose report map contains no REPORT_ID items (e.g. RMK firmware keyboards), the parser reads the report from byte 0, so the prepended byte shifted every field: the modifier bitmap always read as 0x00 and modifier keys (Shift/Ctrl/Alt/GUI) were silently dropped, while array-style keycodes still appeared to work. Pass the report ID through the existing external_report_id parameter instead of prepending it to the data. Devices with report IDs keep the same behavior (the parser uses external_report_id directly), and unnumbered reports are now parsed at the correct offsets. Also fixes a one-byte overread in the notify callback memcpy, where rep_size + 1 bytes were copied from a rep_size-sized buffer. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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Hi! First of all, thank you for this project — the Bluetooth version of HID Remapper solved a real problem for me (using a Bluetooth keyboard with a computer where Bluetooth is not allowed).
Problem
The Bluetooth notify callback unconditionally prepends the report ID byte to report data before passing it to
handle_received_report(). For devices whose report map contains noREPORT_IDitems — which is valid HID —has_report_id_theirsis false, so the parser reads fields starting at byte 0 of the buffer. The prepended byte shifts every field by one: the modifier bitmap always reads as 0x00, so Shift/Ctrl/Alt/GUI are silently dropped, while array-style keycodes still (mostly) work, which makes this easy to miss.Fix
Pass the report ID through the existing
external_report_idparameter instead of prepending it to the data. Devices whose report maps do use report IDs keep the exact same behavior. This also fixes a one-byte overread in the notify callback memcpy (rep_size + 1bytes were copied from arep_size-sized buffer).Tested with
Cornix split keyboard (RMK firmware) — it sends an unnumbered 8-byte boot-style keyboard report over HOGP. Modifiers were dead before this change and fully working after; regression-checked that regular keys still work.
🤖 Generated with Claude Code