Multitouch on Android

Recent versions of Android have some support for multitouch gestures such as pinching. This page gathers the information in our possession about making your panel work with Android.

How to use ENAC's Android version of hid-multitouch

Android relies on the Linux kernel, so all multitouch drivers available in a given version of the kernel can be used in Android systems that rely on this kernel version. This applies in particular to the unified hid-multitouch driver which currently can manage panels from more than a dozen vendors. This driver is available in the Linux kernel since version 2.6.38, but has been backported to several earlier versions.

Unfortunately, Android versions older than 4.0 (Ice cream sandwich) use a variant of the original multitouch Linux protocol while hid-multitouch uses the most recent protocol. For this reason, we distribute an Android-specific version of hid-multitouch. If you can patch and recompile your kernel, the following steps can get you started. Note: the Android-x86 project already contains an appropriate version of hid-multitouch.

  • look up the status of your panel in our list of multitouch devices
  • if your panel is supported in hid-multitouch, get the Android version in the appropriate ...-android branch of the drivers repository from our git base.
  • if your panel is only supported in a device-specific driver, report to "How to add support..." below.

    • How to test your panel

    Some panels on Android tablets have hardware or firmware problems. For instance on a Pixcir/Sintek panel we have observed blind stripes. If you suspect problems you can:

  • use the "Pointer location" app that comes with Android DevTools. Move your finger slowly because otherwise the app will interpolate between the actual positions and you will see points where the panel did not get any actual contact. Be also careful to use only the tip of your finger because some devices detect two contacts when the contact surface is large, and some drivers will interpolate the two contacts to produce their output, once again resulting into artificial points.

  • or use our modified version of "Pointer location" on which traces are remanent: PointerTest.apk (as of 1/5/2010)

  • or compile and install the evtest program from http://cgit.freedesktop.org/~whot/evtest/. Read /proc/bus/input/devices to determine the number N of your device. Then launch 'evtest /dev/input/eventN' and read the output. You will see X and Y coordinates, use them to check for blind zones.

    • How to add support for your panel

    If you own a multitouch panel that is not supported on your Android device, and you are able to compile and install kernel modules, you might be able to add support for your panel.

    Is your panel supported?

  • use lsusb to determine the vendorID/productID of your panel
  • check in our list if your device has a Linux driver.
  • depending on your kernel version, either retrieve the right driver from your kernel sources or download it from the ENAC drivers, using the appropriate branch.

    Patch your kernel if necessary

  • add the driver file to drivers/hid,
  • in the same directory, add the appropriate lines to hid-ids.h, hid-core.c, Makefile and Kconfig.
  • Recompile and reinstall the hid module and the new module to check that everything is fine. See the general Linux howto for details.

    Older kernel version

    If your kernel is older than 2.6.33 (for instance 2.6.32 as found in Android 2.2), you will need to first modify include/linux/hid.h as described in our Linux multitouch howto before recompiling the hid module or the kernel.

    Adapt the driver for Android

    Android uses a variant of the early Linux kernel multitouch protocol. You need to adapt your new driver.

  • modify the _input_mapping function so as to make sure that ABS_MT_TOUCH_MAJOR is published. You can for instance replace ABS_MT_TRACKING_ID in 'case HID_DG_CONTACTID'.
  • modify the _filter_event function so as to make sure that ABS_MT_TOUCH_MAJOR=1 is emitted when a finger first touches the panel, and ABS_MT_TOUCH_MAJOR=0 when it is released. The exact code depends on the driver.
  • Recompile and install the new module.



    • Contact: chatty at enac.fr, benjamin dot tissoires at enac.fr
    Updated Sep 17, 2011.