From a473f03b100da00e5ceb84d408eb867ab5ca6b8c Mon Sep 17 00:00:00 2001
From: Lorenz Stechauner <lorenz.stechauner@necronda.net>
Date: Tue, 13 Jan 2026 19:23:44 +0100
Subject: [PATCH] Add reverse engineered USB protocol specification

---
 README.md       |  4 ++-
 logitech-G29.md | 70 +++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 73 insertions(+), 1 deletion(-)
 create mode 100644 logitech-G29.md

diff --git a/README.md b/README.md
index 18d6ff0..8124b1f 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,5 @@
 
 Device Driver
-============
+=============
+
+[Logitech G29 USB Protocol](logitech-G29.md)
diff --git a/logitech-G29.md b/logitech-G29.md
new file mode 100644
index 0000000..db547ce
--- /dev/null
+++ b/logitech-G29.md
@@ -0,0 +1,70 @@
+
+Logitech G29 USB Protocol
+=========================
+
+- 12 bytes per event
+- Little-endian (= smaller value bytes first)
+
+```
+                                          1
+  0   1   2   3   4   5   6   7   8   9   0   1
++---+---+---+---+---+---+---+---+---+---+---+---+
+|    Buttons    |  Rot  |Gas|Brk|Clt|GrX|GrY|GrZ|
++---+---+---+---+---+---+---+---+---+---+---+---+
+```
+
+- `Buttons`: Bitmask of pressed buttons (mask values are in big endian).
+    - `0x00000001` - ?
+    - `0x0000000E` - Arrow keys
+        - `0x00000000` - Up
+        - `0x00000002` - Right
+        - `0x00000004` - Down
+        - `0x00000006` - Left
+        - `0x00000008` - No arrow key pressed
+    - `0x00000010` - X
+    - `0x00000020` - Square
+    - `0x00000040` - Circle
+    - `0x00000080` - Triangle
+    - `0x00000100` - R1
+    - `0x00000200` - L1
+    - `0x00000400` - R2
+    - `0x00000800` - L2
+    - `0x00001000` - Share
+    - `0x00002000` - Option
+    - `0x00004000` - R3
+    - `0x00008000` - L3
+    - `0x00010000` - Gear 1
+    - `0x00020000` - Gear 2
+    - `0x00040000` - Gear 3
+    - `0x00080000` - Gear 4
+    - `0x00100000` - Gear 5
+    - `0x00200000` - Gear 6
+    - `0x00400000` - Gear reverse
+    - `0x00800000` - Plus
+    - `0x01000000` - Minus
+    - `0x02000000` - Red rotation clockwise
+    - `0x04000000` - Red rotation counterclockwise
+    - `0x08000000` - Return
+    - `0xF0000000` - ?
+- `Rot`: Wheel rotation (little-endian). `0x0000` (leftmost) - `0xFFFF` (rightmost).
+- `Gas`: Gas pedal. `0xFF` (up, default) - `0x00` (down).
+- `Brk`: Brake pedal. `0xFF` (up, default) - `0x00` (down).
+- `Clt`: Clutch pedal. `0xFF` (up, default) - `0x00` (down).
+- `GrX`: Gearshift X axis. ~`0x30` (gear 1+2), ~`0x80` (gear 3+4), ~`0xB0` (gear 5+6+reverse).
+- `GrY`: Gearshift Y axis. ~`0xD0` (gear 1+3+5), ~`0x40` (gear 2+4+6+reverse).
+- `GrZ`: Gearshift Z axis. ~`0x9C` (neutral), ~`0xDC` (pressed down).
+
+
+## Sample event
+
+Sample event:
+```
+08 00 00 00   00 80   ff ff ff   81 80 9c
+```
+
+* No buttons pressed / no gear engaged
+* Wheel rotation at `0x8000` ~ center
+* Gas pedal up
+* Brake pedal up
+* Clutch pedal up
+* Gearshift neutral