Resistive Touch, Trizeps VIII

The Kinetis MCU default firmware of the Trizeps VIII (Mini) includes a code to act as a touch controller.

Config	TOUCHSCREEN_KUK_TR8MCU
Source	/linux_imx/drivers/input/touchscreen/kuk_tr8mcu_touch.c

How to modify Settings

$ cd /sys/bus/i2c/devices/2-0010
/sys/bus/i2c/devices/2-0010$ ls
average  modalias  power      swapxy     x     xraw    ymax  yscale
driver   name      settle     threshold  xmax  xscale  ymin  zraw
input    of_node   subsystem  uevent     xmin  y       yraw

Get a setting or touch value; ie. get the last measured raw x value:

/sys/bus/i2c/devices/2-0010$ cat xraw
41

Change a setting; ie. swap x and y axis and invert the x-axis:

/sys/bus/i2c/devices/2-0010$ echo 3 > swapxy

Value	I2C-Register	Description
xscale	TOUCH_XSCALE_LSB/MSB	The max. value „xraw“ is scaled „x“ to. Typ.: screen-width
yscale	TOUCH_YSCALE_LSB/MSB	The max. value „yraw“ is scaled „y“ to. Typ.: screen-height
xmin	TOUCH_XMIN_LSB/MSB	xraw value, when left edge of screen is touched
xmax	TOUCH_XMAX_LSB/MSB	xraw value, when right edge of screen is touched
ymin	TOUCH_YMIN_LSB/MSB	yraw value, when top edge of screen is touched
ymax	TOUCH_YMAX_LSB/MSB	yraw value, when bottom edge of screen is touched
threshold	TOUCH_CONFIG	Defines trigger level at which a touch-press is detected 0..63
settle	TOUCH_WAITTIME	Time in ms to wait between before measurements
average	TOUCH_AVERAGE	Number of samples to average for each point
swapxy	-	0x0: no change, 0x1: swap x and y axis, 0x2: invert x-axis, 0x4: Invert y-axis
x	TOUCH_XSCALE_LSB/MSB	scaled x value of last measurement (Bitmask 0x8000: no touch press)
y	TOUCH_YSCALE_LSB/MSB	scaled y value of last measurement (Bitmask 0x8000: no touch press)
xraw	TOUCH_XMIN_LSB/MSB	last raw x value
yraw	TOUCH_YMIN_LSB/MSB	last raw y value
zraw	TOUCH_XMAX_Z_LSB/MSB	last raw z value. Z-measurement must be enabled

Device-Tree for resistive Touch-Controller

Example:

&iomuxc {
   pinctrl_restouch: restouchgrp {
      fsl,pins = <
        MX8MM_IOMUXC_SD2_WP_GPIO2_IO20      0x16 /* MCU Interrupt */
      >;
   };
}
&i2c3 {
   touch: kuk_tr8mcu_touch@10 {
      compatible = "kuk,kuk-tr8mcu-touch";
         reg = <0x10>;
         pinctrl-names       = "default";
         pinctrl-0           = <&pinctrl_restouch>;
         interrupts-extended = <&gpio2 20 IRQ_TYPE_LEVEL_LOW>;
         xscale              = <800>;
         yscale              = <480>;
         xmin                = <306>;
         xmax                = <3781>;
         ymin                = <692>;
         ymax                = <3459>;
         settle              = <10>;
         average             = <25>;
         yreverse            = "true" ;
         linux,wakeup;
   };
}

For a description of the settings see table above.
The swapxy is split into 3 values for the device-tree:

swapxy	Swap x and y axis
xreserve	Invert x axis
yreserve	Invert y axis