
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) 
   
   0 to Vmid in 15 steps, 0 = use zero power comparator with Vmid threshold
   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
    ====================================
       0	      21          1
       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