Connecting banana pi m2 zero with ili9341 display over spi on latest armbian image

robertoj · September 16

I tried all weekend to add the touch function of the LCD's XPT2046

With this DTS:

Spoiler

/dts-v1/;
/plugin/;

/ {
compatible = "allwinner,sun8i-h3";
fragment@0 {
	target = <&pio>;
	__overlay__ {
		display_pins: display_pins {
			pins = "PC4", "PA2"; /*reset,dc*/
			function = "gpio_out", "gpio_out";
		};
		ads7846_pins: ads7846_pins {
			pins = "PA19"; /*irq*/
			function = "irq";
		};
		spi0_cs0: spi0_cs0 {
			pins = "PC3";
			function = "gpio_out";
			output-high;
		};
		spi0_cs1: spi0_cs1 {
			pins = "PC7";
			function = "gpio_out";
			output-high;
		};
	};
}; /*closing of fragment@0*/

fragment@1 {
	target = <&spi0>;
	__overlay__ {
		pinctrl-names = "default", "default";
		pinctrl-1 = <&spi0_cs1>;
		cs-gpios = <0>, <&pio 2 7 0>; /* PC7 */
	};
};  /*closing of fragment@1*/

fragment@2 {
	target = <&spi0>;
	__overlay__ {
		/* needed to avoid dtc warning */
		#address-cells = <1>;
		#size-cells = <0>;
		status="okay";
		pinctrl-names = "default", "default"; /*added by ryjelsum*/
		cs-gpios = <&pio 2 3 0>, <&pio 2 7 0>; /* cs0=C3,cs1=C7 */
		#num-chipselects = <2>; /*deleted by ryjelsum*/
		display: display@0 {
			/*compatible = "ilitek,ili9341";*/
			compatible = "adafruit,yx240qv29", "ilitek,ili9341";
			reg = <0>;
			pinctrl-names = "default";
			pinctrl-0 = <&display_pins>;
			pinctrl-1 = <&spi1_cs0>; /*added by ryjelsum*/
			spi-max-frequency = <24000000>;
			status="okay"; /*added by ryjelsum*/
			rotation= <90>;
			bgr = <0>;
			fps = <15>;
			buswidth = <8>;
			height = <320>;
			width = <240>;
			reset-gpios = <&pio 2 4 0>; /* C4,GPIO 24 polarity 0 for adafruit */
			dc-gpios    = <&pio 0 2 0>; /* A2,GPIO 25 */
			debug = <3>;
		};
		ads7846: ads7846@1 { /*this whole block added by ryjelsum*/
			reg = <1>; /* Chip Select 1 */
			compatible = "ti,ads7846";
			spi-max-frequency = <1000000>;
			status = "okay";
			pinctrl-2=<&spi0_cs1 &spi0_cs1>;
			pinctrl-names = "default";
			pinctrl-3 = <&ads7846_pins>;
			interrupt-parent = <&pio>;
			interrupts = <0 19 2>; /* PA19 IRQ_TYPE_EDGE_FALLING */
			pendown-gpio = <&pio 0 19 0>; /* PA19 */
			/* driver defaults, optional */
			ti,x-min = /bits/ 16 <0>;
			ti,y-min = /bits/ 16 <0>;
			ti,x-max = /bits/ 16 <0x0FFF>;
			ti,y-max = /bits/ 16 <0x0FFF>;
			ti,pressure-min = /bits/ 16 <0>;
			ti,pressure-max = /bits/ 16 <0xFFFF>;
			ti,x-plate-ohms = /bits/ 16 <400>;
		};
	};
}; /*closing of fragment@2*/

__overrides__ {
	rotation = <&display>, "rotation:0";
	fps = <&display>, "fps:0";
	debug = <&display>, "debug:0";
}; /* closing of overrides */
};

It gets compiled, but the bootloader rejects it:

Applying user provided DT overlay ili9341-touch-sp0.dtbo

failed on fdt_overlay_apply(): FDT_ERR_NOT_FOUND

Error applying DT overlays, restoring original DT

(i included the spi-add-cs1.dtbo as suggested in https://ryjelsum.me/homelab/xpt2046-ili9341-opi-zero/ )

Ryzer · September 16

Hi robertoj,

I can see some lines that look problematic. Firstly you are defining cs-gpio twice.

Once here:

5 hours ago, robertoj said:

fragment@1 {
	target = <&spi0>;
	__overlay__ {
		pinctrl-names = "default", "default";
		pinctrl-1 = <&spi0_cs1>;
		cs-gpios = <0>, <&pio 2 7 0>; /* PC7 */
	};

Note - Remember that 0 refers to the native cs line (PC3)

5 hours ago, robertoj said:

fragment@2 {
	target = <&spi0>;
	__overlay__ {
		/* needed to avoid dtc warning */
		#address-cells = <1>;
		#size-cells = <0>;
		status="okay";
		pinctrl-names = "default", "default"; /*added by ryjelsum*/
		cs-gpios = <&pio 2 3 0>, <&pio 2 7 0>; /* cs0=C3,cs1=C7 */

Here the pinctrl references are wrong. I am not sure how strictly the ordering matters but for clarity 'pinctrl-names' should be before the actual pin control nodes.

5 hours ago, robertoj said:

pinctrl-2=<&spi0_cs1 &spi0_cs1>;
			pinctrl-names = "default";
			pinctrl-3 = <&ads7846_pins>;

Adding spi-add-cs1.dtbo is not needed as all it does it defined the pins to use as cs lines which you have already done above anyway. My other suggestion would be to look into what the latest bindings should for the ads7846 touch controller. Let me know how you get on with following overlay:

Spoiler

/dts-v1/;
/plugin/;

/ {
compatible = "allwinner,sun8i-h3";
fragment@0 {
    target = <&pio>;
    __overlay__ {
        display_pins: display_pins {
            pins = "PC4", "PA2"; /*reset,dc*/
            function = "gpio_out", "gpio_out";
        };
        ads7846_pins: ads7846_pins {
            pins = "PA19"; /*irq*/
            function = "irq";
        };
        spi0_cs0: spi0_cs0 {
            pins = "PC3";
            function = "gpio_out";
            output-high;
        };
        spi0_cs1: spi0_cs1 {
            pins = "PC7";
            function = "gpio_out";
            output-high;
        };
    };
}; /*closing of fragment@0*/

fragment@1 {
    target = <&spi0>;
    __overlay__ {
        /* needed to avoid dtc warning */
        #address-cells = <1>;
        #size-cells = <0>;
        status="okay";
        pinctrl-names = "default", "default"; /*added by ryjelsum*/
        pinctrl-1 = <&spi0_cs1>; /* pinctrl-0 is already declared in the primary dts */
        cs-gpios = <0>, <&pio 2 7 0>; /* cs0=C3,cs1=C7 */
        num-chipselects = <2>;
        display: display@0 {
            /*compatible = "ilitek,ili9341";*/
            compatible = "adafruit,yx240qv29", "ilitek,ili9341";
            reg = <0>;
            pinctrl-names ="default";
            pinctrl-0 = <&display_pins>;
            spi-max-frequency = <24000000>;
            status="okay";
            rotation= <90>;
            bgr = <0>;
            fps = <15>;
            buswidth = <8>;
            height = <320>;
            width = <240>;
            reset-gpios = <&pio 2 4 0>; /* C4,GPIO 24 polarity 0 for adafruit */
            dc-gpios    = <&pio 0 2 0>; /* A2,GPIO 25 */
            debug = <3>;
        };
        ads7846: ads7846@1 {
            reg = <1>; /* Chip Select 1 */
            compatible = "ti,ads7846";
            spi-max-frequency = <1000000>;
            status = "okay";
            pinctrl-names ="default";
            pinctrl-0 = <&ads7846_pins>;
            interrupt-parent = <&pio>;
            interrupts = <0 19 2>; /* PA19 IRQ_TYPE_EDGE_FALLING */
            pendown-gpio = <&pio 0 19 0>; /* PA19 */
            /* driver defaults, optional */
            ti,x-min = /bits/ 16 <0>;
            ti,y-min = /bits/ 16 <0>;
            ti,x-max = /bits/ 16 <0x0FFF>;
            ti,y-max = /bits/ 16 <0x0FFF>;
            ti,pressure-min = /bits/ 16 <0>;
            ti,pressure-max = /bits/ 16 <0xFFFF>;
            ti,x-plate-ohms = /bits/ 16 <400>;
        };
    };
}; /*closing of fragment@2*/

__overrides__ {
    rotation = <&display>, "rotation:0";
    fps = <&display>, "fps:0";
    debug = <&display>, "debug:0";
}; /* closing of overrides */
};

best of luck

Ryzer

robertoj · September 16

I went with your corrected DTS ... so far it looks great

Spoiler

roberto@bananapim2zero:~$ lsmod |grep ads
ads7846                20480  0
roberto@bananapim2zero:~$ lsmod |grep spi
roberto@bananapim2zero:~$ sudo cat /proc/interrupts | grep ads
[sudo] password for roberto: 
 59:        574          0          0          0  sunxi_pio_edge  19 Edge      ads7846
roberto@bananapim2zero:~$ dmesg | grep spi
[    7.139676] ads7846 spi0.1: supply vcc not found, using dummy regulator
[    7.140801] ads7846 spi0.1: touchscreen, irq 59
[    7.153779] input: ADS7846 Touchscreen as /devices/platform/soc/1c68000.spi/spi_master/spi0/spi0.1/input/input1
[    7.195022] panel-ilitek-ili9341 spi0.0: get optional vcc failed
[    7.196412] [drm] Initialized ili9341 1.0.0 20210716 for spi0.0 on minor 1
[    7.702554] panel-ilitek-ili9341 spi0.0: [drm] Initialized display serial interface
[    7.762184] panel-ilitek-ili9341 spi0.0: [drm] fb0: ili9341drmfb frame buffer device

(Did NOT use the spi-add-cs1.dtbo, as advised)

I went out running to work, and I will continue tests when I go back home

Day 2 of testing:

Spoiler

roberto@bananapim2zero:~$ dmesg | grep ads
[    1.702669] ads7846@1 enforce active low on GPIO handle
[    7.139676] ads7846 spi0.1: supply vcc not found, using dummy regulator
[    7.140801] ads7846 spi0.1: touchscreen, irq 59

roberto@bananapim2zero:~$ sudo cat /sys/kernel/debug/gpio
gpiochip0: GPIOs 0-223, parent: platform/1c20800.pinctrl, 1c20800.pinctrl:
 gpio-0   (CON2-P13            )
 gpio-1   (CON2-P11            )
 gpio-2   (CON2-P22            |dc                  ) out hi 
 gpio-3   (CON2-P15            )
 gpio-4   (CON3-P03            )
 gpio-5   (CON3-P02            )
 gpio-6   (CON2-P07            )
 gpio-7   (CON2-P29            )
 gpio-8   (CON2-P31            )
 gpio-9   (CON2-P33            )
 gpio-10  (CON2-P35            )
 gpio-11  (CON2-P05            )
 gpio-12  (CON2-P03            )
 gpio-13  (CON2-P08            )
 gpio-14  (CON2-P10            )
 gpio-15  (CON2-P16            )
 gpio-16  (CON2-P12            )
 gpio-17  (CON2-P37            )
 gpio-18  (CON2-P28            )
 gpio-19  (CON2-P27            |pendown             ) in  hi IRQ 
 gpio-20  (CON2-P40            )
 gpio-21  (CON2-P38            )
 gpio-64  (CON2-P19            )
 gpio-65  (CON2-P21            )
 gpio-66  (CON2-P23            )
 gpio-67  (CON2-P24            )
 gpio-68  (CON2-P18            |reset               ) out hi 
 gpio-71  (CON2-P26            |spi0 CS1            ) out hi ACTIVE LOW
 gpio-110 (CSI-PWR-EN          )
 gpio-128 (CN3-P17             )
 gpio-129 (CN3-P13             )
 gpio-130 (CN3-P09             )
 gpio-131 (CN3-P07             )
 gpio-132 (CN3-P19             )
 gpio-133 (CN3-P21             )
 gpio-134 (CN3-P22             )
 gpio-135 (CN3-P20             )
 gpio-136 (CN3-P18             )
 gpio-137 (CN3-P16             )
 gpio-138 (CN3-P14             )
 gpio-139 (CN3-P12             )
 gpio-140 (CN3-P05             )
 gpio-141 (CN3-P03             )
 gpio-142 (CN3-P06             )
 gpio-143 (CN3-P08             )
 gpio-160 (SDC0-D1             )
 gpio-161 (SDC0-D0             )
 gpio-162 (SDC0-CLK            )
 gpio-163 (SDC0-CMD            )
 gpio-164 (SDC0-D3             )
 gpio-165 (SDC0-D2             )
 gpio-166 (SDC0-DET            |cd                  ) in  hi 
 gpio-192 (WL-SDIO-CLK         )
 gpio-193 (WL-SDIO-CMD         )
 gpio-194 (WL-SDIO-D0          )
 gpio-195 (WL-SDIO-D1          )
 gpio-196 (WL-SDIO-D2          )
 gpio-197 (WL-SDIO-D3          )
 gpio-198 (BT-UART-TX          )
 gpio-199 (BT-UART-RX          )
 gpio-200 (BT-UART-RTS         )
 gpio-201 (BT-UART-CTS         )
 gpio-202 (WL-WAKE-AP          )
 gpio-203 (BT-WAKE-AP          |host-wakeup         ) in  lo 
 gpio-204 (BT-RST-N            |shutdown            ) out hi 
 gpio-205 (AP-WAKE-BT          |device-wakeup       ) out hi 

gpiochip1: GPIOs 352-383, parent: platform/1f02c00.pinctrl, 1f02c00.pinctrl:
 gpio-353 (CPUX-SET            |vdd-cpux            ) out hi 
 gpio-354 (CON2-P32            )
 gpio-355 (POWER-KEY           |power               ) in  hi IRQ ACTIVE LOW
 gpio-356 (CON2-P36            )
 gpio-357 (VCC-IO-EN           )
 gpio-358 (USB0-ID             |usb0_id_det         ) in  hi IRQ 
 gpio-359 (WL-PWR-EN           |reset               ) out hi ACTIVE LOW
 gpio-360 (PWR-STB             |vcc1v2              ) out hi 
 gpio-361 (PWR-DRAM            |vcc-dram            ) out hi 
 gpio-362 (PWR-LED             |bananapi-m2-zero:red) out lo ACTIVE LOW
 gpio-363 (IR-RX               )

roberto@bananapim2zero:~$ sudo apt install evtest
...done

roberto@bananapim2zero:~$ sudo evtest
No device specified, trying to scan all of /dev/input/event*
Available devices:
/dev/input/event0:	gpio-keys
/dev/input/event1:	ADS7846 Touchscreen
Select the device event number [0-1]: 1
Input driver version is 1.0.1
Input device ID: bus 0x1c vendor 0x0 product 0x1ea6 version 0x0
Input device name: "ADS7846 Touchscreen"
Supported events:
  Event type 0 (EV_SYN)
  Event type 1 (EV_KEY)
    Event code 330 (BTN_TOUCH)
  Event type 3 (EV_ABS)
    Event code 0 (ABS_X)
      Value   3303
      Min        0
      Max     4095
    Event code 1 (ABS_Y)
      Value   2584
      Min        0
      Max     4095
    Event code 24 (ABS_PRESSURE)
      Value  62397
      Min        0
      Max    65535
Properties:
Testing ... (interrupt to exit)
Event: time 1726556440.417809, type 3 (EV_ABS), code 0 (ABS_X), value 3294
Event: time 1726556440.417809, type 3 (EV_ABS), code 1 (ABS_Y), value 2585
Event: time 1726556440.417809, type 3 (EV_ABS), code 24 (ABS_PRESSURE), value 64811
Event: time 1726556440.417809, -------------- SYN_REPORT ------------
Event: time 1726556440.477739, type 3 (EV_ABS), code 0 (ABS_X), value 3303
Event: time 1726556440.477739, type 3 (EV_ABS), code 1 (ABS_Y), value 2584
Event: time 1726556440.477739, type 3 (EV_ABS), code 24 (ABS_PRESSURE), value 63498
...

evtest shows a random stream of events, then stops... then lcd touches dont get reactions.

I will check my wiring and order a new LCD, because mine has a cracked glass

Is there any way to tell that the SPI, IRQ, CS inputs/outputs to the XPT2046 (ADS 7846) is working correctly, and blame everything on a bad resistive panel?

robertoj · September 18

When doing sudo evtest, I get random events. It may be related to https://forum.armbian.com/topic/15271-spi0-cs1-held-low-when-ads7846-is-loaded/

robertoj · September 19

I had some success by changing the touch chip pins from:

CS1=~~PC7~~ PA18 (I avoided the "native Spi0 CS1 PC7" and used PA18)

IRQ=~~PA19~~ PA7 (maybe this was unnecessary)

New DTS:

Spoiler

roberto@bananapim2zero:~/ili9341$ cat ili9341-touch-sp0-ryzer-other-cs1-irq.dts
/dts-v1/;
/plugin/;

/ {
compatible = "allwinner,sun8i-h3";
fragment@0 {
    target = <&pio>;
    __overlay__ {
        display_pins: display_pins {
            pins = "PC4", "PA2"; /*reset,dc*/
            function = "gpio_out", "gpio_out";
        };
        ads7846_pins: ads7846_pins {
            pins = "PA7"; /*irq*/
            function = "irq";
        };
        spi0_cs0: spi0_cs0 {
            pins = "PC3";
            function = "gpio_out";
            output-high;
        };
        spi0_cs1: spi0_cs1 {
            pins = "PA18";
            function = "gpio_out";
            output-high;
        };
    };
}; /*closing of fragment@0*/

fragment@1 {
    target = <&spi0>;
    __overlay__ {
        /* needed to avoid dtc warning */
        #address-cells = <1>;
        #size-cells = <0>;
        status="okay";
        pinctrl-names = "default", "default"; /*added by ryjelsum*/
        pinctrl-1 = <&spi0_cs1>; /* pinctrl-0 is already declared in the primary dts */
        cs-gpios = <0>, <&pio 0 18 0>; /* cs0=PC3,cs1=PA18 */
        num-chipselects = <2>;
        display: display@0 {
            /*compatible = "ilitek,ili9341";*/
            compatible = "adafruit,yx240qv29", "ilitek,ili9341";
            reg = <0>;
            pinctrl-names ="default";
            pinctrl-0 = <&display_pins>;
            spi-max-frequency = <24000000>;
            status="okay";
            rotation= <90>;
            bgr = <0>;
            fps = <15>;
            buswidth = <8>;
            height = <320>;
            width = <240>;
            reset-gpios = <&pio 2 4 0>; /* C4,GPIO 24 polarity 0 for adafruit */
            dc-gpios    = <&pio 0 2 0>; /* A2,GPIO 25 */
            debug = <3>;
        };
        ads7846: ads7846@1 {
            reg = <1>; /* Chip Select 1 */
            compatible = "ti,ads7846";
            spi-max-frequency = <1000000>;
            status = "okay";
            pinctrl-names ="default";
            pinctrl-0 = <&ads7846_pins>;
            interrupt-parent = <&pio>;
            interrupts = <0 7 2>; /* PA7 IRQ_TYPE_EDGE_FALLING */
            pendown-gpio = <&pio 0 7 0>; /* PA7 */
            /* driver defaults, optional */
            ti,x-min = /bits/ 16 <200>;
            ti,y-min = /bits/ 16 <200>;
            ti,x-max = /bits/ 16 <3900>;
            ti,y-max = /bits/ 16 <3900>;
            /*ti,pressure-min = /bits/ 16 <0>;*/
            ti,pressure-max = /bits/ 16 <255>;
            ti,x-plate-ohms = /bits/ 16 <60>;
        };
    };
}; /*closing of fragment@2*/

__overrides__ {
    rotation = <&display>, "rotation:0";
    fps = <&display>, "fps:0";
    debug = <&display>, "debug:0";
}; /* closing of overrides */
};

With inspiration from https://github.com/jonathan-gatard/ili9486-xpt2046/tree/main for the IOs and the analog parameters

Now sudo evtest prints an event each time I press on the LCD screen

Spoiler

roberto@bananapim2zero:~$ sudo evtest
[sudo] password for roberto: 
No device specified, trying to scan all of /dev/input/event*
Available devices:
/dev/input/event0:	gpio-keys
/dev/input/event1:	ADS7846 Touchscreen
Select the device event number [0-1]: 1
Input driver version is 1.0.1
Input device ID: bus 0x1c vendor 0x0 product 0x1ea6 version 0x0
Input device name: "ADS7846 Touchscreen"
Supported events:
  Event type 0 (EV_SYN)
  Event type 1 (EV_KEY)
    Event code 330 (BTN_TOUCH)
  Event type 3 (EV_ABS)
    Event code 0 (ABS_X)
      Value   3312
      Min      200
      Max     3900
    Event code 1 (ABS_Y)
      Value   2579
      Min      200
      Max     3900
    Event code 24 (ABS_PRESSURE)
      Value    238
      Min        0
      Max      255
Properties:
Testing ... (interrupt to exit)
Event: time 1726725202.045512, type 3 (EV_ABS), code 0 (ABS_X), value 3319
Event: time 1726725202.045512, type 3 (EV_ABS), code 1 (ABS_Y), value 2588
Event: time 1726725202.045512, type 3 (EV_ABS), code 24 (ABS_PRESSURE), value 4
Event: time 1726725202.045512, -------------- SYN_REPORT ------------
Event: time 1726725202.885527, type 3 (EV_ABS), code 0 (ABS_X), value 3311
Event: time 1726725202.885527, type 3 (EV_ABS), code 1 (ABS_Y), value 2596
Event: time 1726725202.885527, type 3 (EV_ABS), code 24 (ABS_PRESSURE), value 30
Event: time 1726725202.885527, -------------- SYN_REPORT ------------
Event: time 1726725205.495577, type 3 (EV_ABS), code 0 (ABS_X), value 3280
Event: time 1726725205.495577, type 3 (EV_ABS), code 1 (ABS_Y), value 2560
Event: time 1726725205.495577, type 3 (EV_ABS), code 24 (ABS_PRESSURE), value 43
Event: time 1726725205.495577, -------------- SYN_REPORT ------------
Event: time 1726725206.767507, type 3 (EV_ABS), code 0 (ABS_X), value 3304
Event: time 1726725206.767507, type 3 (EV_ABS), code 1 (ABS_Y), value 2579
Event: time 1726725206.767507, type 3 (EV_ABS), code 24 (ABS_PRESSURE), value 87
...

If an LCD suffers a disconnection and reconnection, is it possible to reset, re-initialize and continue working the LCD?

Or would it always need a Linux reboot?

robertoj · September 22

problem solved: IRQ i/o needed the reverse polarity in pendown-gpio. armbianEnv.txt and DTS here:

(it is working with sudo evtest, so I dont know if it needs calibration... and I wonder if I need to reverse the polarity in the interrupts line too)

Spoiler

roberto@bananapim2zero:~/ili9341$ cat ili9341-touch-sp0.dts
/dts-v1/;
/plugin/;

/ {
compatible = "allwinner,sun8i-h3";
fragment@0 {
    target = <&pio>;
    __overlay__ {
        display_pins: display_pins {
            pins = "PC4", "PA2"; /*reset,dc*/
            function = "gpio_out", "gpio_out";
        };
        ads7846_pins: ads7846_pins {
            pins = "PA7"; /*irq*/
            function = "irq";
        };
        spi0_cs0: spi0_cs0 {
            pins = "PC3";
            function = "gpio_out";
            output-high;
        };
        spi0_cs1: spi0_cs1 {
            pins = "PA18";
            function = "gpio_out";
            output-high;
        };
    };
}; /*closing of fragment@0*/

fragment@1 {
    target = <&spi0>;
    __overlay__ {
        /* needed to avoid dtc warning */
        #address-cells = <1>;
        #size-cells = <0>;
        status="okay";
        pinctrl-names = "default", "default"; /*added by ryjelsum*/
        pinctrl-1 = <&spi0_cs1>; /* pinctrl-0 is already declared in the primary dts */
        cs-gpios = <0>, <&pio 0 18 0>; /* cs0=PC3,cs1=PA18 */
        num-chipselects = <2>;
        display: display@0 {
            /*compatible = "ilitek,ili9341";*/
            compatible = "adafruit,yx240qv29", "ilitek,ili9341";
            reg = <0>;
            pinctrl-names ="default";
            pinctrl-0 = <&display_pins>;
            spi-max-frequency = <24000000>;
            status="okay";
            rotation= <90>;
            bgr = <0>;
            fps = <15>;
            buswidth = <8>;
            height = <320>;
            width = <240>;
            reset-gpios = <&pio 2 4 0>; /* C4,GPIO 24 polarity 0 for adafruit */
            dc-gpios    = <&pio 0 2 0>; /* A2,GPIO 25 */
            debug = <3>;
        };
        ads7846: ads7846@1 {
            reg = <1>; /* Chip Select 1 */
            compatible = "ti,ads7846";
            spi-max-frequency = <1000000>;
            status = "okay";
            pinctrl-names ="default";
            pinctrl-0 = <&ads7846_pins>;
            interrupt-parent = <&pio>;
            interrupts = <0 7 2>; /* PA7 IRQ_TYPE_EDGE_FALLING */
            pendown-gpio = <&pio 0 7 1>; /* PA7 */
            /* driver defaults, optional*/
            ti,x-min = /bits/ 16 <0>;
            ti,y-min = /bits/ 16 <0>;
            ti,x-max = /bits/ 16 <0xFFF>;
            ti,y-max = /bits/ 16 <0xFFF>;
            ti,pressure-min = /bits/ 16 <0>;
            ti,pressure-max = /bits/ 16 <0xFFFF>;
            ti,x-plate-ohms = /bits/ 16 <400>;
        };
    };
}; /*closing of fragment@2*/

__overrides__ {
    rotation = <&display>, "rotation:0";
    fps = <&display>, "fps:0";
    debug = <&display>, "debug:0";
}; /* closing of overrides */
};
roberto@bananapim2zero:~/ili9341$ cat /boot/armbianEnv.txt 
verbosity=1
bootlogo=false
console=both
disp_mode=1920x1080p60
overlay_prefix=sun8i-h3
rootdev=UUID=c809ccbe-42ae-40e8-b871-04e14b950d7a
rootfstype=ext4
user_overlays=ili9341-touch-sp0
usbstoragequirks=0x2537:0x1066:u,0x2537:0x1068:u
roberto@bananapim2zero:~/ili9341$

robertoj · September 22

I could run lightdm with

apt install xinit xterm xauth x11-apps xserver-xorg lightdm xserver-xorg-input-evdev xserver-xorg-video-fbdev

/usr/share/X11/xorg.conf.d/99-fbdev.conf:

Section "Device"

Identifier "myfb"

Driver "fbdev"

Option "fbdev" "/dev/fb0"

EndSection

However, the cursor is moving at 90-degrees from my finger movement. Also, it is very unstable... it crashes, leaving a white screen. The white screen remains after reboot, and I can only make it work again by removing and connecting the 5V power.

Can someone share how they installed a window manager with ili9341?

is 24MHz too fast? Would native cs1 help anything?

robertoj · September 24

https://github.com/raspberrypi/linux/issues/6067

https://github.com/raspberrypi/linux/pull/6029

https://forums.raspberrypi.com/viewtopic.php?p=2206990&hilit=ads7846#p2206990

https://github.com/raspberrypi/bookworm-feedback/issues/88

There seems to be some instability in the ads7846 driver in the latest linux. If anyone is having a good experience with ads7846, please indicate how you did it.

Ryzer · September 25

Hi robertoj,

There are addtional touchscreen parameters that you could try to address the cursor movement being wrong. based on what you have said I would suggest adding the line 'ti,swap-xy = <1>;' to:

ads7846: ads7846@1 {
            reg = <1>; /* Chip Select 1 */
            compatible = "ti,ads7846";
            spi-max-frequency = <1000000>;
            status = "okay";
            pinctrl-names ="default";
            pinctrl-0 = <&ads7846_pins>;
            interrupt-parent = <&pio>;
            interrupts = <0 7 2>; /* PA7 IRQ_TYPE_EDGE_FALLING */
            pendown-gpio = <&pio 0 7 1>; /* PA7 */
            /* driver defaults, optional*/
            ti,x-min = /bits/ 16 <0>;
            ti,y-min = /bits/ 16 <0>;
            ti,x-max = /bits/ 16 <0xFFF>;
            ti,y-max = /bits/ 16 <0xFFF>;
            ti,pressure-min = /bits/ 16 <0>;
            ti,pressure-max = /bits/ 16 <0xFFFF>;
            ti,x-plate-ohms = /bits/ 16 <400>;
        };

In regards to the crashing that, will be a bit harder to pin down. Thinking about I would suggest double checking 'interrupts = <0 7 2>;' as I would have expected it to be something like 'interrupts = <0 7 IRQ_TYPE_EDGE_FALLING>. That said, it does appear to be registering correctly when looking here:

On 9/16/2024 at 4:26 PM, robertoj said:
gpio-19  (CON2-P27            |pendown             ) in  hi IRQ 

Does /proc/interrupts list the gpio as being set to trigger on falling edge as expected?

24MHz is the maximum speed that the ili9341 will work at in spi mode. It may be possible that there indeed problems with the driver but without investigating deeper its hard to say. Raspberry Pi have there own distinct linux kernel fork so the problems mentioned may not be common to the mainline kernel used by Armbian. I wonder if the crashes are possibly caused by the cs lines of both devices being pulled low at the same time under certain conditions.

best of luck

Ryzer

Edited September 25 by Ryzer

robertoj · September 26

Thank you. I will try that, and I learned about the xinput_calibrator, which I will apply next time.

(and https://github.com/reinderien/xcalibrate/blob/main/xcalibrate is a new interesting project)

Now I am focusing on moving the touchscreen pins to an independent gpio-based SPI set of pins... we will know whether the LCD crash is from interfering SPI commands.

I did an experiment with the "backlight = <&backlight_gpio>" parameter as shown in https://github.com/beagleboard/bb.org-overlays/blob/master/src/arm/BB-LCD-ADAFRUIT-24-SPI0-00A0.dts

and https://forums.raspberrypi.com/viewtopic.php?t=358240 but so far it ended up in a kernel not loading. I will leave this task for last.

If the DTS configuration does not specify CPHA and CPOL, what is the default setting of the SPI protocol?

robertoj · September 29

I decided to use the gpio-spi driver, to emulate software spi just for the touch chip ADS7846/XPT2048, and use a different DTS file

Here is what I think would work: ads7846-spi-gpio.dts

Spoiler

/* Configure the GPIO to handle ADS7846 touch surface chip
with the gpio-spi driver:
https://www.kernel.org/doc/Documentation/devicetree/bindings/spi/spi-gpio.txt
https://stackoverflow.com/questions/78905378/how-do-i-use-spi-gpio-driver-in-linux
https://gist.github.com/BjoernSch/39d3bca950a3b025b806decc2b686bbc

*/

/dts-v1/;
/plugin/;

/ {
compatible = "allwinner,sun4i-a10", "allwinner,sun7i-a20", "allwinner,sun8i-h3", "allwinner,sun50i-a64", "allwinner,sun50i-h5";
fragment@0 {
	target = <&pio>;
	__overlay__ {
		ads7846_pins: ads7846_pins {
			pins = "PA1"; /*irq*/
			function = "irq";
		};
	};
};

fragment@1 {
	/*target = <&spi-gpio>; /* what goes here ???? */
	target-path = "/"; /* what goes here ???? */
	__overlay__ {
		my_new_spi {
		compatible = "spi-gpio";
		/* needed to avoid dtc warning */
		#address-cells = <1>;
		ranges;
		status="okay";
		mosi-gpios = <&pio 0 12 0>; /*t_din= PA12*/
		sck-gpios = <&pio 0 11 0>;  /*t_clk= PA11*/
		miso-gpios = <&pio 0 6 0>;  /*t_dout=PA6*/
		cs-gpios = <&pio 0 0 0>;    /*t_cs=  PA0*/
		num-chipselects = <1>;
		ads7846: ads7846@1 {
			reg = <0>; /* Chip Select 0 on this separate SPI bus */
			compatible = "ti,ads7846";
			spi-max-frequency = <1000000>;
			status = "okay";
			pinctrl-names ="default";
			pinctrl-0 = <&ads7846_pins>;
			interrupt-parent = <&pio>;
			interrupts = <0 1 2>; /* PA1 IRQ_TYPE_EDGE_FALLING */
			pendown-gpio = <&pio 0 1 1>; /* PA1 */
			/* driver defaults, optional*/
			ti,x-min = /bits/ 16 <0>;
			ti,y-min = /bits/ 16 <0>;
			ti,x-max = /bits/ 16 <0xFFF>;
			ti,y-max = /bits/ 16 <0xFFF>;
			ti,pressure-min = /bits/ 16 <0>;
			ti,pressure-max = /bits/ 16 <0xFFFF>;
			ti,x-plate-ohms = /bits/ 16 <400>;
			ti,swap-xy = <1>;
		};
		}; //end of my_new_spi
	};
};

};

I used these references:

https://www.kernel.org/doc/Documentation/devicetree/bindings/spi/spi-gpio.txt
https://stackoverflow.com/questions/78905378/how-do-i-use-spi-gpio-driver-in-linux
https://gist.github.com/BjoernSch/39d3bca950a3b025b806decc2b686bbc

and need to check this too:

http://terminal28.blogspot.com/2015/12/bitbanging-spi-on-raspberry-pi-via-spi.html

http://terminal28.blogspot.com/2016/05/enabling-spi1-on-raspberry-pi-bzero23.html

My DTS compiles well but the linux in my armbian image did not include spi-gpio.ko, in /lib/modules/6.6.44-current-sunxi/kernel/drivers/spi/

Therefore, I am building a new OS image.

Does anyone see a problem with my DTS?

Update:) it works good stability

now the only problem is that both x-axis and y-axis are reversed (not swapped). More updates on the way

Ryzer · September 30

Hi robertoj,

On 9/26/2024 at 5:03 PM, robertoj said:

If the DTS configuration does not specify CPHA and CPOL, what is the default setting of the SPI protocol?

This would most like be set somewhere within the SPI controller driver.

I tried that in my other post with not much success but I will try to give it another shot.

maybe you could try reversing the min and max values

best of luck

Ryzer

robertoj · October 1

I simply rotated the image with the "rotation" parameter in the LCD DTS, and turned the screen 180 degrees physically.

I will try the min, max swap later, but right now I am on a roll, making my tkinter apps work

Another thing I will try is not using a chip select pin at all, since LCD and touch-chip are on different buses now.

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Connecting banana pi m2 zero with ili9341 display over spi on latest armbian image

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