---
name: tactility-bluetooth
description: Use when debugging or extending Bluetooth/BLE in Tactility OS — BLE HID Host (central) for keyboards/mice/combo touchpads, Report ID stripping, mouse report parsing (Fosmon-style standard vs Logitech 12-bit), NimBLE scan cache including nameless/RPA devices, PUBLIC vs RANDOM addr_type fallback, and auto-connect/reconnect retry loops.
version: 1.0.0
author: Hermes Agent
license: MIT
metadata:
  hermes:
    tags: [tactility, bluetooth, ble, hid-host, nimble, esp32, esp32s3, combo-keyboard, auto-connect]
    related_skills: [tactility-firmware, systematic-debugging]
---

# Tactility Bluetooth / BLE HID Host

## Overview
Tactility's BLE stack uses NimBLE host (ESP-IDF) on ESP32/S3. Central role (HID Host) connects to external keyboards, mice, and combo keyboard+touchpad devices. Relevant for:

- Fosmon Mini BT Keyboard w/ Touchpad (Amazon B00BX0YKX4 / https://a.co/d/0fg4vprm) — keyboard Report ID 1 + mouse/touchpad Report ID 2, 4-5 byte reports `[buttons, x, y, wheel, pan]`
- Generic combo devices that sleep, advertise without name, use RPA (Resolvable Private Address)

Builds require `device.py <id>` to generate sdkconfig; simulator POSIX path has no BT.

## When to Use
- Mouse doesn't move / jumps erratically on combo KB+touchpad
- Bluetooth won't reconnect to previously paired KB/mouse after sleep
- Adding new HID Host behavior, touchpad gestures, consumer reports
- Debugging `BLE_HS_EALREADY`, `addr_type`, bond loss, `hid_host_active` flag
- Changing scan filter, RSSI, adv parsing

Don't use for USB HID (`usb_host_hid`) or classic BT (Tactility uses BLE only for HID host).

## Architecture

### Key Files
- `Platforms/platform-esp32/source/drivers/bluetooth/esp32_ble_scan.cpp` — GAP DISC event handler, `scan_results[64]` + `scan_addrs[64]`, `ble_gap_disc_event_handler`, `ble_resolve_next_unnamed_peer`
- `Platforms/platform-esp32/source/drivers/bluetooth/esp32_ble.cpp` — advertising helpers, dispatch_enable/disable, `hid_host_active` atomic guard against simultaneous central connect
- `Platforms/platform-esp32/private/bluetooth/esp32_ble_internal.h` — `BleCtx`, `scan_mutex`, `hid_host_active`
- `Tactility/Source/bluetooth/BluetoothHidHost.cpp` — central connection state machine: service/char/disc, CCCD subscribe chain, Report Map read, type resolution, `NOTIFY_RX` dispatch, LVGL indev registration
- `Tactility/Source/bluetooth/Bluetooth.cpp` — `bt_event_bridge`, `SCAN_FINISHED -> autoConnectHidHost()`, `PROFILE_STATE_CHANGED IDLE -> rescan`
- `Tactility/Source/app/btmanage/*` + `btpeersettings/*` — UI, manual connect calls `hidHostConnect(addr)` directly

### Flow
```
DISC callback -> cacheScanAddr + scan_results -> BT_EVENT_PEER_FOUND -> getScanResults()
SCAN_FINISHED -> autoConnectHidHost() iterates scanResults, checks PairedDevice autoConnect + profile BT_PROFILE_HID_HOST -> hidHostConnect()
hidHostConnect: getCachedScanAddrType() for addr_type -> ble_gap_connect() -> GAP CONNECT -> security_initiate -> disc_all_svcs -> disc_all_chrs -> disc_all_dscs -> read Report Ref + Report Map -> type resolution -> CCCD subscribe -> ready
NOTIFY_RX: find rpt by valHandle -> switch type -> handleKeyboard/Mouse with reportId
```

## Combo Device Quirks — Fosmon Example

From Amazon B00BX0YKX4 (Fosmon Mini Bluetooth Keyboard QWERTY + Touchpad):
- Dual HID: keyboard (boot-like 8-byte mod+reserved+6keys) + mouse (3-5 byte relative)
- Uses Report IDs: ID 1 keyboard, ID 2 mouse; Report Map has two top-level collections `0x05 0x01 0x09 0x06 A1 01 85 01 ...` and `0x09 0x02 A1 01 85 02 ...`
- Some NimBLE stacks notify raw char value INCLUDING ID byte: `[0x02, buttons, x, y]` vs expected `[buttons, x, y]`
- Sleeps quickly, wakes on keypress with directed advertising (RPA, no name, ~30s window)

## Mouse Report Parsing — Pitfall & Fix (2026-07-13)

### Old Bug
```cpp
if (len >= 5) { // assumed Logitech 12-bit packed
  raw_x = data[2] | ((data[3]&0x0F)<<8); sign-extend 12-bit
  raw_y = (data[3]>>4) | (data[4]<<4);
}
```
Cheap touchpads send standard 4/5-byte `[btn, x8, y8, wheel, pan]`. Above decodes wheel byte as nibble → huge jumps.

### Fix Pattern (dual-heuristic)
1. Implement `*Internal(data,len,expected_report_id)` variants that strip leading ID if `expected_report_id !=0 && data[0]==id`.
2. For `plen>=5`, try both:
   - std: `dx=(int8)p[1], dy=(int8)p[2]`
   - 12-bit: `raw_x12 = p[2] | ((p[3]&0x0F)<<8)`, `raw_y12 = (p[3]>>4)|(p[4]<<4)` sign-extend 12-bit
3. Heuristic:
   - `std_small = abs(dx)<=48 && abs(dy)<=48`, `s12_large = abs(raw_x12)>128 || abs(raw_y12)>128`
   - If std_small && s12_large → prefer std (touchpad with wheel byte)
   - If s12_large and raw_12 plausible `<=300` and std huge `>64` or `p[1]==0` → prefer 12-bit (Logitech)
   - Else std
4. Always dispatch via Internal with `rpt.reportId` so ID stripped.

See `references/mouse-report-parsing.md`.

## BLE Scan Inclusive Caching — Pitfall & Fix

### Old Bug
`esp32_ble_scan.cpp:90` filtered nameless:
```cpp
if (!found && record.name[0] != '\0' && scan_count<64) // store only named
```
Bonded KB after sleep advertises only appearance+flags or directed (no name), uses RPA that rotates. Result:
- `scan_results` empty for that MAC
- `scan_addr_cache` misses → `getCachedScanAddrType()` fails → default PUBLIC, but device may be RANDOM → `ble_gap_connect rc!=0`
- `autoConnectHidHost()` never finds peer

### Fix
- Store ALL unique advertisers regardless of name. Still set `should_publish = name[0]!= '\0'` for UI cadence if needed, but cache must include nameless.
- On duplicate, always update `scan_addrs[i] = disc.addr` to track RPA rotation.
- `getScanResults()` now returns nameless too — UI shows "Unknown (aabbcc...)" which is useful for debugging; optionally filter weak RSSI in View layer.

See `references/scan-and-reconnect.md`.

## Reconnect — Addr Type & Retry

### Persistent auto-connect on boot (fix 2026-07-12)
Previous `autoConnectHidHost()` only connected if peer was seen in last scan. On reboot Fosmon is asleep → scan empty → no connect, and retry timer was only created inside `hidHostConnect()` so boot chain died after 1st scan.

Fix implemented in `BluetoothHidHost.cpp`:
- `ensureAutoConnTimer()` lazy creates `hid_autoconn_retry_timer`, called from `autoConnectHidHost()` itself (exists at boot)
- `hid_autoconn_empty_scan_count` tracks consecutive empty scans
- Phase 1: if peer in scanResults → connect with fresh addr_type + RSSI log
- Phase 2: not in scan but saved autoConnect peer exists:
  - After `HID_AUTOCONN_DIRECT_AFTER=1` empty scan → direct `hidHostConnect(saved_addr)` even without advert — NimBLE does internal 8s scan/connect trying both PUBLIC/RANDOM
  - On fail → reschedule timer 3s (fast), 10s, 30s (backoff) forever → catches wake on keypress (~30s directed adv window)
- Counter resets on successful connect, stops timer on connect

User confirmed: "keyboard mouse combo works great now" after mouse parse fix, but "If the board restart, it won't autoconnect" — this persistent direct-connect fixed it.

### Addr Type Fallback
NimBLE store can hold RANDOM, but cache lookup may miss. Pattern:
```cpp
ble_addr.type = PUBLIC; memcpy val
if (getCachedScanAddrType(...,&type)) type= cached;
rc = ble_gap_connect(..., PUBLIC, ...)
if (rc!=0 && type==PUBLIC) retry RANDOM;
if (rc!=0 && cached==RANDOM) retry PUBLIC;
```
Log which type used. Timeout 5s → 8s for slow wake.

### Periodic Retry Timer
Keyboard wakes on keypress for ~30s directed adv. If scan ended just before wake, single rescan misses it. Add `hid_autoconn_retry_timer` esp_timer (ESP_TIMER_TASK):
- Created lazily in `hidHostConnect`
- Stopped on successful connect
- In `autoConnectHidHost()` when device not found but autoConnect peers exist: `esp_timer_start_once(retry_timer, 3*1e6)`
- Callback `hidAutoConnRetryCb` starts scan if not scanning; `SCAN_FINISHED` -> `autoConnectHidHost()` again.

Prevent tight loop after manual disconnect? TODO in code: if user manually disconnects and autoConnect still true, it will keep retrying. Separate toggle or respect manual intent.

### `hid_host_active` Guard
`BleCtx.hid_host_active` prevents simultaneous central connections during `ble_resolve_next_unnamed_peer` name resolution (would fail `BLE_HS_EALREADY`). Set true in `hidHostConnect`, false on disconnect/connect fail.

## Build Env Pitfall (Hermes venv pollution)

From 2026-07-11/13 sessions:
- Hermes desktop venv Python 3.11 `pydantic` (3.11 `pydantic_core`) leaks via `PYTHONPATH` into ESP-IDF 3.9 env → `ModuleNotFoundError: pydantic_core._pydantic_core` or `TypeError: unsupported operand type(s) for |`
- Toolchain xtensa `xtensa-esp32s3-elf-gcc` not in PATH when PATH stripped to only idf env
- Also, if `ESP_IDF_VERSION` env unset, CMakeLists chooses simulator path → `Unknown CMake command idf_build_get_property` + SDL detection `SDL Threads needed` even after `device.py`

Fix wrapper (board-direct per user 2026-07-12 — **never simulator** for BT/driver changes, user said "Don't compile for simulator is a waste of time, build for the board directly"):
```bash
cd firmware
rm -rf build sdkconfig  # required when lvgl.fontSize changed or switching python envs
env -u PYTHONPATH -u PYTHONHOME -u ESP_IDF_VERSION -u IDF_PATH \
  PATH=$HOME/.espressif/python_env/idf5.3_py3.9_env/bin:$HOME/.espressif/tools/xtensa-esp-elf/esp-13.2.0_20240530/xtensa-esp-elf/bin:/Users/adolforeyna/esp/esp-idf/tools:/opt/homebrew/bin:/usr/bin:/bin \
  python device.py waveshare-esp32-s3-rlcd
grep FONT_SIZE sdkconfig  # verify 14/18/24 after font bump
# then
env -u PYTHONPATH -u PYTHONHOME \
  PATH=...same... IDF_PATH=/Users/adolforeyna/esp/esp-idf ESP_IDF_VERSION=5.3 \
  idf.py -p /dev/cu.usbmodem1101 flash
```
User preference: "Don't compile for simulator is a waste of time, build for the board directly." Enforced 2026-07-12.
For font bumps: always `rm -rf build` after editing `device.properties` lvgl.fontSize, else old `TT_LVGL_TEXT_FONT_DEFAULT_SIZE=14` stays cached.

Quick sanity without full build: `grep -rn "hidHostHandleMouseReport\|hid_host_ctx\|scan_results" firmware/ --include="*.cpp" --include="*.h"`
env -u PYTHONPATH -u PYTHONHOME -u ESP_IDF_VERSION -u IDF_PATH \
  PATH=$HOME/.espressif/python_env/idf5.3_py3.9_env/bin:$HOME/.espressif/tools/xtensa-esp-elf/esp-13.2.0_20240530/xtensa-esp-elf/bin:/Users/adolforeyna/esp/esp-idf/tools:/opt/homebrew/bin:/usr/bin:/bin \
  python device.py waveshare-esp32-s3-rlcd
# then
env -u PYTHONPATH ...same PATH... idf.py build
# flash
env -u PYTHONPATH ... idf.py -p /dev/cu.usbmodem1101 flash
```
User preference: "Don't compile for simulator is a waste of time, build for the board directly." Enforced 2026-07-12.

Quick sanity without full build: `grep -rn "hidHostHandleMouseReport\|hid_host_ctx\|scan_results" firmware/ --include="*.cpp" --include="*.h"`

## Common Pitfalls
1. Assuming 5-byte mouse = 12-bit. Always implement dual heuristic.
2. Forgetting Report ID strip — combo devices include ID. Pass `rpt.reportId` to handler.
3. Filtering scan to named only — breaks bonded auto-connect. Cache all, filter UI only.
4. Not updating `scan_addrs` on duplicate — RPA rotation missed.
5. Only trying PUBLIC — many keyboards use RANDOM RPA. Always fallback.
6. Single scan after disconnect — misses wake window. Use 3s retry timer.
7. `hid_host_active` not cleared on connect fail — blocks future name resolution.

## References
- `references/combo-keyboard-mouse.md` — Fosmon report map structure, ID table, sleep/wake behavior
- `references/mouse-report-parsing.md` — dual-decode code snippet + test vectors
- `references/scan-and-reconnect.md` — inclusive cache patch, addr_type matrix, retry timer pattern