Add Twiddler 4 configs (firmware 3.8.0+)

README.md

@@ -84,8 +84,23 @@ for handling some cross-situations when the walk fails between certain keys.
 It's recommended to learn the walk with `mirrorwalk_nomcc` first and really
 learn the walk since if you *can* do the walk it's faster than releasing
 the finger to press the few single-finger chord letters available in my
-latest version of mirrorwalk. 
+latest version of mirrorwalk.
 
+## Twiddler 4 Configs
+
+The `configs/t4/` folder contains configs for **Twiddler 4** with firmware 3.8.0+.
+
+- `default.cfg` - Factory default (for reference)
+- `mirrorwalk_nomcc.cfg` - Mirrorwalk layout ready to use
+- `mirrorwalk_nomcc.json` - For practice at [tutor.mytwiddler.com](https://tutor.mytwiddler.com/tutor2/settings.html)
+
+**Important**: Twiddler Tuner generates configs with version 0x0107 which crashes
+firmware 3.8.0+. The T4 configs here use the correct version 0x0907 and include
+system chords for config switching (Thumb Num + Row 4 Middle) and Bluetooth
+cycling (Thumb Num + Row 4 Right).
+
+To install: copy to `1.CFG` on the Twiddler USB storage, unmount, disconnect,
+then press T0+F4M to switch configs.
 
 ## Cheat-sheet template
 

configs/t4/README.md

@@ -0,0 +1,51 @@
+# Twiddler 4 Configs
+
+Configuration files for Twiddler 4 with firmware 3.8.0+.
+
+## Files
+
+- `default.cfg` - Factory default config (for reference and system chords)
+- `mirrorwalk_nomcc.cfg` - Mirrorwalk layout with system chords
+- `mirrorwalk_nomcc.json` - Mirrorwalk for Tutor practice (tutor.mytwiddler.com)
+
+## Installation
+
+1. Connect Twiddler 4 via USB-C
+2. Mount the USB storage (FAT12 filesystem)
+3. Copy config to `1.CFG` (or `2.CFG`)
+4. Unmount and disconnect USB
+5. Press T0+F4M (Thumb Num + Row 4 Middle) to switch configs
+
+## Important Notes
+
+### Firmware Version Compatibility
+
+These configs use format version 0x0907 which is required for firmware 3.8.0+.
+Configs generated by Twiddler Tuner use version 0x0107 which will crash the device.
+
+### System Chords
+
+The configs include system chords from the default config for:
+- Config switching (T0+F4M)
+- Bluetooth cycling (T0+F4R)
+- Mouse buttons
+
+Some system chords conflict with mirrorwalk letter positions (p, y, etc.) and are
+omitted to preserve the layout. Essential functions (config/BT switching) are preserved.
+
+### Known Issue: Bluetooth Erase (N+S+4R)
+
+The Bluetooth erase chord (T14+F4R / N+S+4R) does not work with mirrorwalk_nomcc.cfg
+due to a firmware quirk: having N+4L mapped to '0' (HID 0x27) interferes with the
+N+S+4R system chord recognition.
+
+**Workaround**: Switch to `0.CFG` (default config) when you need to erase Bluetooth
+pairings, then switch back to your custom config:
+1. Press T0+F4M to cycle to config 0 (3 green LEDs)
+2. Press N+S+4R to erase Bluetooth pairings (blue scanning animation)
+3. Press T0+F4M to return to config 1
+
+## Tools
+
+See https://github.com/yourusername/twiddler for Python tools to convert and
+manipulate Twiddler 4 configs.