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Wolfson Microelectronics WM9705 and WM9712 Touchscreen Controllers

===================================================================

The WM9705 and WM9712 are high performance AC97 audio codecs with built

in touchscreen controllers that are mainly found in portable devices.

i.e. Dell Axim and Toshiba e740.

This driver uses the AC97 link controller for all communication with the

codec and can be either built into the kernel or built as a module.

Build Instructions

==================

The driver will be built into the kernel if "sound card support" = y and

"wolfson AC97 touchscreen support" = y in the kernel sound configuration.

To build as a module, "wolfson AC97 touchscreen support" = m

in the kernel sound configuration.

Driver Features

===============

 * supports WM9705, WM9712

 * polling mode

 * coordinate polling

 * adjustable rpu/dpp settings

 * adjustable pressure current

 * adjustable sample settle delay

 * 4 and 5 wire touchscreens (5 wire is WM9712 only)

 * pen down detection

 * power management

 * AUX ADC sampling

Driver Usage

============

In order to use this driver, a char device called wm97xx with a major

number of 10 and minor number 16 will have to be created under

/dev/touchscreen.

e.g.

mknod /dev/touchscreen/wm97xx c 10 16

Driver Parameters

=================

The driver can accept several parameters for fine tuning the touchscreen.

However, the syntax is different between module options and passing the

options in the kernel command line.

e.g.

rpu=1   (module)

rpu:1   (kernel command line)

1. Codec sample mode. (mode)

   The WM9712 can sample touchscreen data in 3 different operating

   modes. i.e. polling, coordinate and continous.

   Polling:-     The driver polls the codec and issues 3 seperate commands

                 over the AC97 link to read X,Y and pressure.

   Coordinate: - The driver polls the codec and only issues 1 command over

                 the AC97 link to read X,Y and pressure. This mode has

                 strict timing requirements and may drop samples if

                 interrupted. However, it is less demanding on the AC97

                 link. Note: this mode requires a larger delay than polling

                 mode.

   Continuous:-  The codec automatically samples X,Y and pressure and then

                 sends the data over the AC97 link in slots. This is then

                 same method used by the codec when recording audio.

   Set mode = 0 for polling, 1 for coordinate and 2 for continuous.

   Default mode = 0

2. WM9712 Internal pull up for pen detect. (rpu)

   Pull up is in the range 1.02k (least sensitive) to 64k (most sensitive)

   i.e. pull up resistance = 64k Ohms / rpu.

   Adjust this value if you are having problems with pen detect not

   detecting any down events.

   Set rpu = value

   Default rpu = 1

3. WM9705 Pen detect comparator threshold. (pdd)

   i.e. 1 =  Vmid/15 threshold

        15 =  Vmid/1 threshold

   Adjust this value if you are having problems with pen detect not

   detecting any down events.

   Set pdd = value

   Default pdd = 0

4. Set current used for pressure measurement. (pil)

   Set pil = 2 to use 400uA

       pil = 1 to use 200uA and

       pil = 0 to disable pressure measurement.

   This is used to increase the range of values returned by the adc

   when measureing touchpanel pressure.

   Default pil = 0

5. WM9712 Set 5 wire touchscreen mode. (five_wire)

   Set five_wire = 1 to enable 5 wire mode on the WM9712.

   Default five_wire = 0

   NOTE: Five wire mode does not allow for readback of pressure.

6. ADC sample delay. (delay)

   For accurate touchpanel measurements, some settling time may be

   required between the switch matrix applying a voltage across the

   touchpanel plate and the ADC sampling the signal.

   This delay can be set by setting delay = n, where n is the array

   position of the delay in the array delay_table below.

   Long delays > 1ms are supported for completeness, but are not

   recommended.

   Default delay = 4

    wm_delay     uS     AC97 link frames

    ====================================

       1              42          2

       2          84          4

       3         167          8

       4         333         16

       5         667         32

       6        1000         48

       7        1333         64

       8        2000         96

       9        2667        128

      10        3333        160

      11        4000        192

      12        4667        224

      13        5333        256

      14        6000        288

      15           0          0 (No delay, switch matrix always on)

Contact

=======

Further information about the WM9705 and WM9712 can be found on the

Wolfson Website. http://www.wolfsonmicro.com

Please report bugs to liam.girdwood@wolfsonmicro.com or

                      linux@wolfsonmicro.com