Need Help setup Touch on LVDS Display

gerko · July 23, 2025, 5:37pm

I’m asking for help setting up an LVDS touch display.
The display works with an adapter on the Apalis’ LVDS2.

I’d now like to add touch functionality.
I’m afraid the HYCON touch controller is connected to Apalis ~~SPI0~~ I2C0 … that is, to pins 132 and 126, ~~and in parallel to pins 211 and 209~~.
The carrier board is based on the Ixora carrier board.

My attempts to copy a dto together have failed.
Here is my attempt, which compiles and deploys but has no effect:

// SPDX-License-Identifier: GPL-2.0-or-later OR MIT
/*
* Copyright 2020-2021 Toradex
*/
// Enable a generic LVDS display on port 2.
#include <dt-bindings/gpio/gpio.h>
#include <dt-bindings/interrupt-controller/irq.h>

/dts-v1/;
/plugin/;
/ {
    compatible = "toradex,apalis-imx8";
};


/* I2C Bus, an dem der Touchcontroller angeschlossen ist (z.B. i2c1) */

&i2c1 {
    status = "okay";

    hycon_touch: touch@38 {
        compatible = "hycon,hy46xx"; // Replace with your controller's compatible string
        reg = <0x38>;  // 0111 000 0|1 0x38 OK?
        interrupt-parent = <&lsio_gpio2>;
        interrupts = <28 IRQ_TYPE_EDGE_FALLING>;
        reset-gpios = <&lsio_gpio2 29 GPIO_ACTIVE_LOW>;
        touchscreen-size-x = <800>;
        touchscreen-size-y = <480>;
    };
};


&ldb2 {
...


...
...




tdx-info

Software summary
------------------------------------------------------------
Bootloader:               U-Boot
Kernel version:           5.15.148-6.7.0-devel+git.f437ddb7191d #1-TorizonCore SMP PREEMPT Mon Jul 1 08:03:31 UTC 2024
Kernel command line:      root=LABEL=otaroot rootfstype=ext4 quiet logo.nologo vt.global_cursor_default=0 plymouth.ignore-serial-consoles splash fbcon=map:3 ostree=/ostree/boot.1/torizon/9a5da750768d3006a86133f6bd7f2a2ee54a44dd2fca5f2e52ccb086cdf86784/0
Distro name:              NAME="TorizonCore"
Distro version:           VERSION_ID=6.7.0-devel-20240701080203-build.0
Distro variant:           VARIANT="Docker"
Hostname:                 apalis-imx8-07279028
------------------------------------------------------------

Hardware info
------------------------------------------------------------
HW model:                 Toradex Apalis iMX8QM V1.1 on Apalis Ixora V1.2 Carrier Board
Toradex version:          0037 V1.1E
Serial number:            07279028
Processor arch:           aarch64
------------------------------------------------------------

Best
Gerald

ToradexAI · July 23, 2025, 5:37pm

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Hello Gerald,

Thank you for the detailed information. Let’s break down your setup and where you might adjust things to enable touch functionality with your HYCON touch controller.

Key Points from Your Message

Display on LVDS2 is shown correctly.
HYCON touch controller is connected via SPI0 (not I2C) to Apalis pins 132 (MOSI), 126 (MISO), 211 (SCK), and 209 (CS).
Device tree overlay attempts so far have treated the controller as I2C (i2c1).
Running on TorizonCore 6.7.0-devel, Ixora carrier board V1.2.

1. Recognizing the Protocol

Your touch controller is connected via SPI, but your overlay is using I2C!
The block you wrote configures a hypothetical device on I2C1 at address 0x38, which won’t work, as the hardware is physically on SPI0, not I2C1.

For touch operation to work, we need:

a compatible driver for the HYCON controller over SPI
a correct device tree overlay, binding the controller node under the relevant &ecspi (SPI) node

2. Device Tree Overlay Example for SPI Touch

Let’s assume a generic approach here – since the actual HYCON driver may or may not be present in the Toradex kernel, but this is how you’d set up a SPI device:

/dts-v1/;
/plugin/;

/ {
    compatible = "toradex,apalis-imx8";
};

&ecspi1 { // Apalis SPI1 is on ecspi1
    status = "okay";

    hycon_touch: hycon@0 {
        compatible = "hycon,hy46xx"; // This must match the driver's expected string
        reg = <0>; // Chip Select 0 (use <1> for CS1)
        spi-max-frequency = <1000000>; // Touch controllers typically use up to 1MHz
        interrupt-parent = <&lsio_gpio2>;
        interrupts = <28 IRQ_TYPE_EDGE_FALLING>;  // Set to your INT GPIO
        reset-gpios = <&lsio_gpio2 29 GPIO_ACTIVE_LOW>; // Set to your RESET GPIO, if connected
        touchscreen-size-x = <800>;
        touchscreen-size-y = <480>;
    };
};

You’ll need to ensure:

The correct SPI bus and chip select are selected (ecspi1, and reg = <0> for CS0).
The pinmuxing for the used pins is properly set (sometimes this needs a pinctrl block).
The compatible string matches an available kernel driver; if not present, the device won’t be bound and show up.

3. Pin Mapping

Apalis SPI1 maps to ecspi1.
Pins 132/126/211/209 correspond to SPI MOSI/MISO/SCK/CS. You can cross-check this in the Apalis iMX8 datasheet.
lsio_gpio2 28 and 29 are exemplary for INT and RESET; ensure these match your circuit.

4. Check for Driver Availability

The line:

compatible = "hycon,hy46xx";

is only valid if this driver is available in your TorizonCore kernel. You can check this by running:

zcat /proc/config.gz | grep HYCON

or by looking at /sys/bus/spi/drivers/ to see if a suitable driver is present.

If there is no HYCON touch driver in the kernel, the overlay alone won’t work. Additional effort will be needed to supply such a driver, likely requiring kernel module development.

5. Additional Steps

Make sure the SPI bus and chip select are accessible and not already used by other peripherals.
Once the overlay is in place and deployed, check /dev/input/ for a new touch device when you boot.
You can also monitor dmesg with dmesg | grep spi or dmesg | grep -i touch to see if the device is detected and bound.

References

Summary:

Your overlay currently targets I2C, but hardware is on SPI.
Adjust overlay as above for SPI.
Confirm kernel driver support for your touch controller.
Monitor dmesg and /dev/input/ for device appearance.

If you provide the exact HYCON controller part number, I may be able to offer a more targeted configuration example.

Best regards,
Toradex AI Assistant.

gerko · July 23, 2025, 7:33pm

OK, if I do this: zcat /proc/config.gz | grep HYCON
the response is:
# CONFIG_TOUCHSCREEN_HYCON_HY46XX is not set

looks like I have to use yocto.

rudhi.tx · July 24, 2025, 8:56am

Hello @gerko,

Thanks for investigating this and reporting the results. We can enable this config for you in our following nightly builds. I am submitting a request to our Torizon R&D team to do that for you. Therefore, you don’t have to go through Yocto.

I will let you know once it is enabled.

gerko · July 24, 2025, 9:35am

Oh, that’s great.

However, I’m using a BSP already created in Yocto. My changes wouldn’t be included in the new nightly build.

And:

I can compile and add the Hycon driver as an external kernel module in TorizonCoreBuilder. I’ve now succeeded.

I’m afraid I still have a problem with the pin configuration for the interrupt and nRESET pins.

/* I2C Bus, an dem der Touchcontroller angeschlossen ist (z.B. i2c1) */
/* i2c2 is APALIS I2C1 ?? */
&i2c2 {
    status = "okay";

    hycon_touch: touch@38 {
        compatible = "hycon,hy46xx"; // Replace with your controller's compatible string
        reg = <0x38>;  // I2C-Adresse des Touchcontrollers
        interrupt-parent = <&lsio_gpio2>;
        interrupts = <28 IRQ_TYPE_EDGE_FALLING>;
        reset-gpios = <&lsio_gpio2 29 GPIO_ACTIVE_LOW>;
        touchscreen-size-x = <800>;
        touchscreen-size-y = <480>;
		// pinctrl-names = "default";
		// pinctrl-0 = <&pinctrl_gpio_touch_interrupt>;
		status = "okay";

    };
};

is this correct … can this work or have I to define a pinctrl node?

rudhi.tx · July 25, 2025, 12:24pm

I can compile and add the Hycon driver as an external kernel module in TorizonCoreBuilder. I’ve now succeeded.

That is indeed one way to do it. Glad to hear that you have succeeded in it.

In order to help you with the pin configuration for interrupt and reset signals, I need to know how you are connecting the touch controller to the Ixora Board. I am interested in knowing about what the physical connection looks like.

gerko · July 27, 2025, 12:33pm

I hope the following screenshot is sufficient … ?

rudhi.tx · July 30, 2025, 3:00pm

Hello @gerko,

Thanks for the schematics. I asked for it to compare it with our connections on the Ixora board for our LVDS display for Apalis iMX8QM. Looking into our default device tree I see (in imx8-apalis-ixora-v1.2.dtsi):

atmel_mxt_ts: touch@4a {
                compatible = "atmel,maxtouch";
                interrupt-parent = <&lsio_gpio4>;
                interrupts = <1 IRQ_TYPE_EDGE_FALLING>;         /* Apalis GPIO5 */
                pinctrl-names = "default";
                pinctrl-0 = <&pinctrl_gpio5>, <&pinctrl_gpio6>;
                reg = <0x4a>;
                reset-gpios = <&lsio_gpio4 2 GPIO_ACTIVE_LOW>;  /* Apalis GPIO6 */
                status = "disabled";
        };

You can see this node and other relevant nodes enabled in the eoverlay file apalis-imx8_panel-cap-touch-10inch-lvds_overlay.dts.

Similarly, in your case you have to choose the right gpio as the interrupt-parent, create pinctrl for your touch controller etc. I see that you are using pins 183 and 181 for your RESET and INT signals. Have you created a pinctrl for your hycon touch using these? It should look something like:

pinctrl_hycon_touch: hycon_touch_pins {
        fsl,pins = <
            IMX8QM_ESAI0_TX2_RX3_LSIO_GPIO2_IO28 0x00000021 /* TOUCH.INT */
            IMX8QM_ESAI0_TX3_RX2_LSIO_GPIO2_IO29 0x00000021 /* TOUCH.nRESET */
        >;

Looking at the pins you use, the interrupt parent should be lsio_gpio2. These are some hints. I think you will have to try it based on our reference device tree.

rudhi.tx · August 5, 2025, 8:45am

Hello @gerko,

I have an update for you. The hycon touch control config support has been added to Torizon OS 7.4.0-devel-202508 version. You may test it on the latest nightly.

In the meantime, do you have any updates on the pin configuration topic?

gerko · August 8, 2025, 2:07pm

Thank you!
I’m currently working on another problem.
I’ll let you know as soon as I’ve made progress.