PROCESSOR-SDK-AM62X: touch screen coordinates mismatch

Hi Swapna,

I have assigned your query to our expert. He is currently out of office until 10/30. So expect a delay in response.

Apologies for the delay.

Best Regards,

Suren

Hi Suren,

Did you get a chance to look into this issue?

please let us know.

Thanks and Regards,

Swapna

Hello Swapna,

1) What touchscreen are you using?

2) How is the touchscreen connected to the AM62x? 

3) What SDK version are you using?

4) please show us the Linux devicetree settings for the touchscreen

5) How are you calibrating the touchscreen?

6) Are you using a touch pen for the calibration? I have seen that give more accurate results than using a finger with resistive touch screens in the past.

Regards,

Nick

Hi Nick,

Here are the details:

1) What touchscreen are you using?

   We are using ADS7843 touch screen controller for our resistive touch LCD (Hantronix's 5.7 inch  HDA570ST-V LCD.

2) How is the touchscreen connected to the AM62x? 

TCH-NIRQ is connected to GPIO pin of the Processor.

3) What SDK version are you using?

SDK: 08.06.00.42

4) please show us the Linux devicetree settings for the touchscreen

     &main_spi2 {
        pinctrl-names = "default";
        pinctrl-0 = <&spitouch_pins_default>;
        status = "okay";
        ti,pindir-d0-out-d1-in;
                
    
        ads7843@0 {
            pinctrl-names = "default";
            pinctrl-0 = <&main_gpio0_ads_intr_pins_default>;

            reg = <0>;    /* CS0 */
            compatible = "ti,ads7843";
            interrupt-parent = <&main_gpio0>;
            interrupts = <1 0>;
            spi-max-frequency = <100000>;
            pendown-gpio = <&main_gpio0 1 0>;
            //vcc-supply = <&vcc_3v3_sys>; Do not uncomment this line

            ti,x-min = /bits/ 16 <0>;
            ti,x-max = /bits/ 16 <4096>;
            ti,y-min = /bits/ 16 <0>;
            ti,y-max = /bits/ 16 <4096>;
            ti,x-plate-ohms = /bits/ 16 <40>;
            //ti,y-plate-ohms = /bits/ 16 <200>;
            ti,pressure-max = /bits/ 16 <255>;

            ti,vref-delay-usecs = <20000>;
            ti,vref-mv      = <3300>;
            ti,keep-vref-on    =  <1>;

            ti,debounce-rep =  <1>;
            ti,debounce-tol =  <30>;
            ti,debounce-max =  <10>;
            

            ti,settle-delay-usec  = /bits/ 16 <150>;
            ti,penirq-recheck-delay-usecs = /bits/ 16 <20000>;

            
            touchscreen-x-mm    = <115>;
            touchscreen-y-mm    = <86>;


            wakeup-source;
        };
    };

5) How are you calibrating the touchscreen?

By deleting the  ws-calibrate.rules.

rm /etc/udev/rules.d/ws-calibrate.rules
rm /run/media/mmcblk0p1/ws-calibrate.rules
reboot

6) Are you using a touch pen for the calibration? I have seen that give more accurate results than using a finger with resistive touch screens in the past.

We are using touch pen as well as normal pen to calibrate the Screen.

Thanks and regards,

Swapna

Hello Swapna,

Thank you for the response. I'll take a look at your device tree settings on Monday and get back to you.

Regards,

Nick

Hello Swapna,

To confirm, are you still seeing similar coordinates after calibration when you touch the corners of the screen? Your coordinates from 3 weeks ago look about what I would expect for touching all 4 corners:

https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1278967/processor-sdk-am62x-touch-screen-interrupt-issue/4856803#4856803

It has been a couple years since I looked at resistive touchscreens. Back then, using Weston instead of tslib tended to give much worse calibration results. e.g., https://e2e.ti.com/support/processors-group/processors/f/processors-forum/862817/am3358-touchscreen-error/3197806#3197806 , 

Are you using a Weston-based graphics system? I haven't checked yet to see what the current default is for our SDK.

Regards,

Nick

Hi Nick,

Yes, the coordinates are still same, no improvement there.

We are using Weston Graphic system and SDK version is 08.06.00.42.

Display used is Hantronix 5.7 inch (HDA570ST-V).

Regards,

Swapna

Hello Swapna,

Your coordinates from 3 weeks ago are expected. If the touchscreen coordinates go from 0 to 4000 for both x and y, it is common to get a touch result that is around 100-300 away from 0 or 4000 when you are touching right on the edge of the screen. I do not see any problems here:

As far as this statement:
"I've to press a bit to the right and a bit down of the button."

Are you able to change the behavior by doing the calibration differently? (e.g., what happens when you try pressing the calibration points at an offset?)

Once we get the correct ws-calibrate.rules settings, I would expect that you could just use those same settings on all of your other boards without having to do manual calibration.

If touchscreen with Weston / Wayland is not working the way you want, you could try rebuilding without those components to see if touchscreen performance improves. (again, I have not played around with this in the last several years, so I am not sure what the current behavior is here).
Notes from the last time I tried that are here: https://e2e.ti.com/support/processors-group/processors/f/processors-forum/862817/am3358-touchscreen-error/3197806#3197806
And you can find information about how to do a yocto build without the mentioned components here: https://software-dl.ti.com/processor-sdk-linux/esd/AM62X/08_06_00_42/exports/docs/linux/Overview_Building_the_SDK.html#common-variations

Regards,

Nick