In a previous post I explained that I built a cross-platform (GNU/Linux and Windows) HID communication layer with asynchronous read and write capabilities. On GNU/Linux, it uses the libusb, which sadly can’t be used at the same time as the HID input driver. Fortunately, the UHID driver allows to pipe the HID input reports from libusb (userspace) to the HID input driver (kernelspace). One issue that arises when using UHID is that the generic HID input driver applies deadzones to all axes, which is a questionable choice… Anyway, this complicates the setup as this requires to calibrate the wheel. I realized that modifying all the Joystick and Gamepad usages to the Multiaxis Controller usage in the HID report descriptor makes the kernel not to apply undesired deadzones. This removes the need for a calibration step!
When using Logitech wheels in both GNU/Linux and Windows, the pedals axes are translated by the operating system from an absolute range (e.g. [0..255] with 255 the rest value) to a relative range ([-32767..32767] with 32767 the rest value). The existing GIMX axis translation parameters (dead zone, sensitivity, acceleration) do not allow to translate the pedal axes back to an absolute range. To fix this, I added joystick correction parameters to the configuration files, that can be configured in a new “Joystick corrections” panel of the existing “Overall” panel (in gimx-config). The default configuration files for the Momo Racing, the DFGT and the G27 contain these new parameters. These files can be downloaded using the “Help>Download Configs” menu item (in gimx-launcher).
When connecting a Logitech wheel to the Raspberry Pi running Raspbian Jessie, the wheel remains in compatibility mode (making the wheel behave as a Driving Force wheel for example). This makes the default configurations unusable. One work-around to this is to use LTWheelConf to enable the native mode, but it’s not convenient as it has to be done again after each reboot. I decided to automatically enable the native mode in GIMX. When starting GIMX, all Logitech wheel connected to the system are switched to their native modes.
Expect these improvements in GIMX 5.2!help