Logitech USB steering wheel

Overview

The Logitech Speed Force Wireless Wheel system uses a USB dongle to connect to the wheel using a propriatory 2.4GHz wireless link. The wheel is intended to sit on one's lap and is powered by a 'wall wart'. The wheel has a 270 degree 'swing', has D pad, 7 buttons and 2 analogue paddles on the rear of the wheel.

The dongle contains a Cypress micro controller and nRF24L01 transceiver, the circuit is similar to this. The switch on the rear of the dongle is used to trigger a re-bonding, although the wireless link is not active until configured. The LED flashes initially to indicate 'not bonded' and then goes out when the link is established, it flashes briefly as data is received from the wheel.

The wheel hardware contains the nRF24L01, a ATMEGA micro, and a PWM/Full-bridge driver for controlling the motor. The micro scans the buttons mounted on the wheel, digitises the wheel/accelerator/brake positions and sends the data to the PC/Dongle.

Supported games are (reputed to be):

• F1 2009
• Speed Zone
• Dirt 2
• Ferrari Challenge
• Need for Speed Undercover

This wheel is currently (Sept 2010) on clearance for less than $10, an obvious attraction to the hard-core hacker. This page describes the protocol to assist in making this wheel work with other systems. This wheel is extremely similar to the PS2/PS3 Driving Force Wireless wheel, so the information is expected to apply to that too...

Protocol

The dongle is a standard USB HID device. The feature port is used to configure the dongle/wireless link, the in-port reads data from the wheel and the out-port is used to send Force Feedback commands.

HID Joystick

The dongle has the USB ID 0x046D:0xC29C, the HID descriptor is (unfortunately) corrupt. Under Windows XP the device is seen as a HID device with a combined X/Y axis, Z axis and 11 buttons. Under Linux the device is seen as HID device with X, Y and Z axis, but no buttons.

05 01 09 04 A1 01 A1 02 95 01 75 0A 15 00 26 FF
03 35 00 46 FF 03 09 30 81 02 06 00 FF 95 02 75
01 25 01 45 01 09 01 81 02 95 0B 19 01 29 0B 05
09 81 02 06 00 FF 95 01 75 01 09 02 81 02 05 01
75 08 26 FF 00 46 FF 00 09 31 09 32 95 02 81 02
C0 A1 02 06 00 FF 95 07 09 03 91 02 C0 0A FF FF
95 08 B1 02 C0

The solution (on Linux) is to re-write the descriptor on the fly, after that the axis/buttons are recognized correctly (even though the wireless link is not active yet).

       if ((quirks & LG_WIIWHEEL) && rsize >= 101 && 
                       rdesc[41] == 0x95 && rdesc[42] == 0x0B &&
                       rdesc[47] == 0x05 && rdesc[48] == 0x09) {
               dev_info(&hdev->dev, "fixing up Logitech WiiWheel button "
                               "descriptor\n");
               rdesc[41] = 0x05;
               rdesc[42] = 0x09;
               rdesc[47] = 0x95;
               rdesc[48] = 0x0B;
       }

Configuration

The Wheel/Dongle are configured by writing to the feature port of the USB dongle. This allows the control of the 'on-air' features, such as initiating the wireless link, controlling the RF channel/hooping sequence and RF addressing (sub-channel coding).

When first plugged in the wireless link between the dongle and the wheel is not active, the link can be 'brought up' with writing the '0xAF Command' followed by the '0xB2 Command'.

Configure RX/TX Address?

Byte 1 - 0xA9

Byte 2 - 2nd and 4th Address/Sub-Channel Bytes

Byte 3 = 3rd and 5th Address/Sub-Channel Bytes

Note 1st Sub-Channel byte is always 0xAE

RF Test Mode

Byte 1 = 0xAC

Byte 2 = Test Mode

0 - Normal Mode (LED flashes on/off as normal)

1 - Constant TX (LED on), RF channel in 'P3' (can kill WiFi ;-)

2 - Pulsed TX (LED flashes long-on/short-off)

3 - Receive Only? (LED off), RF channel in 'P3'. Continually polls nRF24L01 status and clears

Byte 3 - RF Channel/Frequency

Initialise communications

Byte 1 - 0xAF

Byte 2 - Hopping Sequence (0x00..0x0F)

Change RX/TX Address

Byte 1 - 0xB2

Byte 2 - 2nd and 4th Address/Sub-Channel Bytes

Byte 3 = 3rd and 5th Address/Sub-Channel Bytes

Note 1st Sub-Channel byte is always 0xAE

The following do not cause SPI activity to the nRF24L01

Check Status?

Byte 1 - 0xA8

Returns RX/TX Address bytes in Byte 5 and Byte 6

Returns 'button' pressed in Byte 7 bit 5

Returns something in Byte 7 bits 4..0 related to 'LED mode' (not a direct map)

Returns something in Byte 8 which depends on Byte 2 sent

LED Mode

Byte 1 - 0xAA

Byte 2 - changes the way the LED flashes, unknown what is actually happening

Unknown

Byte 1 - 0xAE

Doesn't clear Byte 1 bit 7, like the other commands. Perhaps it is waiting for something...

Returns 0x14 in Byte 5 and 0x00 in Byte 6

Active Address?

Byte 1 - 0xB3

Only clears Byte 1 bit 7 if Command '0xAF' is issued first

Returns values in Byte 5 and Byte 6 which are the values from Command '0xB2' Bytes 2 & 3

Force Feedback

There are a number of force feed back codes which can be written to the USB out-port, some of these are know/understood but assistance is required to further reverse engineer the rest.

The Force Feedback configuration is sent continuously over the wireless link, which takes the form of a 31 byte payload. The wheel is capable of supporting 4 simultaneous effects, plus an additional auto-center effect. The various effects are upload into 'slots', the format is as follows:

Bytes 1..2 - Negotiated SubChannel Address

Bytes 3..4 - Unknown

Bytes 5..10 - Effect Slot 1

Bytes 11..16 - Effect Slot 2

Bytes 17..22 - Effect Slot 3

Bytes 23..28 - Effect Slot 4

Bytes 29..30 - Auto Center

Byte 31 - Unknown, Checksum?

The selected slot for an effect is encoded into the 1st byte of the OUT-Endpoint write. Multiple effects can be active at any time, but it is unknown how multiple forces are rationalized by the wheel.

0x11 : Slot 1

0x21 : Slot 2

0x31 : Slots 1 + 2

0x41 : Slot 3

0x51 : Slots 3 + 1

0x61 : Slots 3 + 2

0x71 : Slots 3 + 2 + 1

0x81 : Slot 4

0x91 : Slots 4 + 1

0xA1 : Slots 4 + 2

0xB1 : Slots 4 + 2 + 1

0xC1 : Slots 4 + 3

0xD1 : Slots 4 + 3 + 1

0xE1 : Slots 4 + 3 + 2

0xF1 : Slots 4 + 3 + 2 + 1

0x_E : Auto Center

The type of effect is encoded in the second byte of the out-port write, with specific settings for the effect in the further bytes.

AutoCenter - fixed position spring, force gets stronger the larger the displacement

Byte 2 - 0x0D

Byte 3 - Proportion of force anti-clockwise (0x00..0x07)

Byte 4 - Proportion of force clockwise (0x00..0x07)

Byte 5 - Force (0x00..0xFF)

Byte 6 & 7 - No effect, set 0x00

Constant Force

Byte 2 - 0x10

Byte 3 - Force Clockwise and Anticlock (0x00..0xFF - 00x00 is to right, 0x80 is zero force, 0xFF is to left)

Byte 4..7 - No effect, set 0x00

Auto/Anti Center (Complex)

This is similar to a spring force, but force is constant towards/away from angle points. Multiple of these can be stacked in different slots to emulate a spring and any angle.

Byte 2 - 0x11

Byte 3 - Clockwise angle, nominally on left (0x00..0xFF - 0x00 is fully left)

Byte 4 - Anti-Clockwise angle, nominally on right(0x00..0xFF)

Byte 5 - L/R Proportion force, upper nymble Clockwise + lower nymble Anticlockwise (each 0x0..0xF)

Byte 6 - Reverse Direction; upper nymble Clockwise + lower nymble Anticlockwise (each 0x0..0x1)

Byte 7 - Force (0x00..0xFF)

Friction Force

Byte 2 - 0x12

Byte 3 - Clockwise force (0x00..0x0F)

Byte 4 - Clockwise Resist = 0x00, Assist = 0x01..0x0F

Byte 5 - Anticlockwise force (0x00..0x0F)

Byte 6 - Anticlockwise Resist = 0x00, Assist = 0x01..0x0F

Byte 7 - No effect, set 0x00.

Auto/Anti Center (Complex)

Is this any different to '0x11'?

Byte 2 - 0x13

Byte 3 - Clockwise angle, nominally on left (0x00..0xFF)

Byte 4 - Anti-Clockwise angle, nominally on right(0x00..0xFF)

Byte 5 - L/R Proportion force, upper nymble Clockwise + lower nymble Anticlockwise (each 0x0..0xF)

Byte 6 - Reverse Direction; upper nymble Clockwise + lower nymble Anticlockwise (each 0x0..0x1)

Byte 7 - Force (0x00..0xFF)

De-associate

this is probably unintentional, the result of not correctly understanding the proper operation of the wheel.

Byte 2 - 0x_F

Byte 3, 4, 5, 6 & 7 - anything (set 0x00)

Testing/Hacking

I have submitted a patch for Linux to support these wheels, this should be in the next mainline kernel (2.6.36rc6?). For those using Debian/Ubuntu you can find a pre-built kernel and headers here.

I managed to get some time on a Wii with Dirt2 and get some captures of the SPI traffic to the nRF24L01 (get them here). Fairly disappointing game, as they don't appear to be doing much in the way of FF. Looking at the data structures, they seem to be using specific 'slots' for each effect:

• Slot 1 - Constant Force
• Slot 2 - Friction
• Slot 3 - Spring
• Slot 4 - <nothing>
• Auto-Center turned on at fixed throughout the whole of the game.

A simple Linux/Python script for testing these codes can be found here.

Apparently there is a port of LibUSB to Windows, it may be possible to produce a small application which would enable the wireless interface without the need to write a full Windows driver. Interestingly the dongle/wheel remain bonded through a reboot of a PC, so the link can be enable in Linux and then the wheel will work under XP (with the corrupted axis mapping).