ADC Based touchscreen

[TuAFBogey]

#
# Input Device Drivers
#
CONFIG_INPUT_KEYBOARD=y
# CONFIG_KEYBOARD_ADC is not set
# CONFIG_KEYBOARD_ADP5588 is not set
# CONFIG_KEYBOARD_ADP5589 is not set
# CONFIG_KEYBOARD_ATKBD is not set
# CONFIG_KEYBOARD_QT1050 is not set
# CONFIG_KEYBOARD_QT1070 is not set
# CONFIG_KEYBOARD_QT2160 is not set
# CONFIG_KEYBOARD_DLINK_DIR685 is not set
# CONFIG_KEYBOARD_LKKBD is not set
CONFIG_KEYBOARD_GPIO=y
# CONFIG_KEYBOARD_GPIO_POLLED is not set
# CONFIG_KEYBOARD_TCA6416 is not set
# CONFIG_KEYBOARD_TCA8418 is not set
# CONFIG_KEYBOARD_MATRIX is not set
# CONFIG_KEYBOARD_LM8323 is not set
# CONFIG_KEYBOARD_LM8333 is not set
# CONFIG_KEYBOARD_MAX7359 is not set
# CONFIG_KEYBOARD_MCS is not set
# CONFIG_KEYBOARD_MPR121 is not set
# CONFIG_KEYBOARD_NEWTON is not set
# CONFIG_KEYBOARD_OPENCORES is not set
# CONFIG_KEYBOARD_SAMSUNG is not set
# CONFIG_KEYBOARD_STOWAWAY is not set
# CONFIG_KEYBOARD_SUNKBD is not set
# CONFIG_KEYBOARD_OMAP4 is not set
# CONFIG_KEYBOARD_TM2_TOUCHKEY is not set
# CONFIG_KEYBOARD_XTKBD is not set
# CONFIG_KEYBOARD_CAP11XX is not set
# CONFIG_KEYBOARD_BCM is not set
CONFIG_KEYBOARD_MA35D1=y
CONFIG_INPUT_MOUSE=y
CONFIG_MOUSE_PS2=y
CONFIG_MOUSE_PS2_ALPS=y
CONFIG_MOUSE_PS2_BYD=y
CONFIG_MOUSE_PS2_LOGIPS2PP=y
CONFIG_MOUSE_PS2_SYNAPTICS=y
CONFIG_MOUSE_PS2_SYNAPTICS_SMBUS=y
CONFIG_MOUSE_PS2_CYPRESS=y
CONFIG_MOUSE_PS2_TRACKPOINT=y
# CONFIG_MOUSE_PS2_ELANTECH is not set
# CONFIG_MOUSE_PS2_SENTELIC is not set
# CONFIG_MOUSE_PS2_TOUCHKIT is not set
CONFIG_MOUSE_PS2_FOCALTECH=y
CONFIG_MOUSE_PS2_SMBUS=y
# CONFIG_MOUSE_SERIAL is not set
# CONFIG_MOUSE_APPLETOUCH is not set
# CONFIG_MOUSE_BCM5974 is not set
# CONFIG_MOUSE_CYAPA is not set
# CONFIG_MOUSE_ELAN_I2C is not set
# CONFIG_MOUSE_VSXXXAA is not set
# CONFIG_MOUSE_GPIO is not set
# CONFIG_MOUSE_SYNAPTICS_I2C is not set
# CONFIG_MOUSE_SYNAPTICS_USB is not set
# CONFIG_INPUT_JOYSTICK is not set
# CONFIG_INPUT_TABLET is not set
CONFIG_INPUT_TOUCHSCREEN=y
CONFIG_TOUCHSCREEN_PROPERTIES=y
CONFIG_TOUCHSCREEN_MA35D1=y
# CONFIG_TOUCHSCREEN_ADS7846 is not set
# CONFIG_TOUCHSCREEN_AD7877 is not set
# CONFIG_TOUCHSCREEN_AD7879 is not set
# CONFIG_TOUCHSCREEN_ADC is not set
CONFIG_TOUCHSCREEN_AR1021_I2C=y
# CONFIG_TOUCHSCREEN_ATMEL_MXT is not set
# CONFIG_TOUCHSCREEN_AUO_PIXCIR is not set
# CONFIG_TOUCHSCREEN_BU21013 is not set
# CONFIG_TOUCHSCREEN_BU21029 is not set
# CONFIG_TOUCHSCREEN_CHIPONE_ICN8318 is not set
# CONFIG_TOUCHSCREEN_CY8CTMA140 is not set
# CONFIG_TOUCHSCREEN_CY8CTMG110 is not set
# CONFIG_TOUCHSCREEN_CYTTSP_CORE is not set
# CONFIG_TOUCHSCREEN_CYTTSP4_CORE is not set
# CONFIG_TOUCHSCREEN_DYNAPRO is not set
# CONFIG_TOUCHSCREEN_HAMPSHIRE is not set
# CONFIG_TOUCHSCREEN_EETI is not set
# CONFIG_TOUCHSCREEN_EGALAX is not set
# CONFIG_TOUCHSCREEN_EGALAX_SERIAL is not set
# CONFIG_TOUCHSCREEN_EXC3000 is not set
# CONFIG_TOUCHSCREEN_FUJITSU is not set
CONFIG_TOUCHSCREEN_GOODIX=y
# CONFIG_TOUCHSCREEN_HIDEEP is not set
# CONFIG_TOUCHSCREEN_ILI210X is not set
# CONFIG_TOUCHSCREEN_S6SY761 is not set
# CONFIG_TOUCHSCREEN_GUNZE is not set
# CONFIG_TOUCHSCREEN_EKTF2127 is not set
# CONFIG_TOUCHSCREEN_ELAN is not set
# CONFIG_TOUCHSCREEN_ELO is not set
# CONFIG_TOUCHSCREEN_WACOM_W8001 is not set
# CONFIG_TOUCHSCREEN_WACOM_I2C is not set
# CONFIG_TOUCHSCREEN_MAX11801 is not set
# CONFIG_TOUCHSCREEN_MCS5000 is not set
# CONFIG_TOUCHSCREEN_MMS114 is not set
# CONFIG_TOUCHSCREEN_MELFAS_MIP4 is not set
# CONFIG_TOUCHSCREEN_MTOUCH is not set
# CONFIG_TOUCHSCREEN_IMX6UL_TSC is not set
# CONFIG_TOUCHSCREEN_INEXIO is not set
# CONFIG_TOUCHSCREEN_MK712 is not set
# CONFIG_TOUCHSCREEN_PENMOUNT is not set
# CONFIG_TOUCHSCREEN_EDT_FT5X06 is not set
# CONFIG_TOUCHSCREEN_TOUCHRIGHT is not set
# CONFIG_TOUCHSCREEN_TOUCHWIN is not set
# CONFIG_TOUCHSCREEN_PIXCIR is not set
# CONFIG_TOUCHSCREEN_WDT87XX_I2C is not set
CONFIG_TOUCHSCREEN_USB_COMPOSITE=y
CONFIG_TOUCHSCREEN_USB_EGALAX=y
CONFIG_TOUCHSCREEN_USB_PANJIT=y
CONFIG_TOUCHSCREEN_USB_3M=y
CONFIG_TOUCHSCREEN_USB_ITM=y
CONFIG_TOUCHSCREEN_USB_ETURBO=y
CONFIG_TOUCHSCREEN_USB_GUNZE=y
CONFIG_TOUCHSCREEN_USB_DMC_TSC10=y
CONFIG_TOUCHSCREEN_USB_IRTOUCH=y
CONFIG_TOUCHSCREEN_USB_IDEALTEK=y
CONFIG_TOUCHSCREEN_USB_GENERAL_TOUCH=y
CONFIG_TOUCHSCREEN_USB_GOTOP=y
CONFIG_TOUCHSCREEN_USB_JASTEC=y
CONFIG_TOUCHSCREEN_USB_ELO=y
CONFIG_TOUCHSCREEN_USB_E2I=y
CONFIG_TOUCHSCREEN_USB_ZYTRONIC=y
CONFIG_TOUCHSCREEN_USB_ETT_TC45USB=y
CONFIG_TOUCHSCREEN_USB_NEXIO=y
CONFIG_TOUCHSCREEN_USB_EASYTOUCH=y
# CONFIG_TOUCHSCREEN_TOUCHIT213 is not set
# CONFIG_TOUCHSCREEN_TSC_SERIO is not set
# CONFIG_TOUCHSCREEN_TSC2004 is not set
# CONFIG_TOUCHSCREEN_TSC2005 is not set
# CONFIG_TOUCHSCREEN_TSC2007 is not set
# CONFIG_TOUCHSCREEN_RM_TS is not set
# CONFIG_TOUCHSCREEN_SILEAD is not set
# CONFIG_TOUCHSCREEN_SIS_I2C is not set
# CONFIG_TOUCHSCREEN_ST1232 is not set
# CONFIG_TOUCHSCREEN_STMFTS is not set
# CONFIG_TOUCHSCREEN_SUR40 is not set
# CONFIG_TOUCHSCREEN_SURFACE3_SPI is not set
# CONFIG_TOUCHSCREEN_SX8654 is not set
# CONFIG_TOUCHSCREEN_TPS6507X is not set
# CONFIG_TOUCHSCREEN_ZET6223 is not set
# CONFIG_TOUCHSCREEN_ZFORCE is not set
# CONFIG_TOUCHSCREEN_ROHM_BU21023 is not set
# CONFIG_TOUCHSCREEN_IQS5XX is not set
# CONFIG_TOUCHSCREEN_ZINITIX is not set
# CONFIG_INPUT_MISC is not set
# CONFIG_RMI4_CORE is not set

in dtsi file;

adc0: adc@40420000 {
	// To use hybrid ADC driver (IIO+TS) for touch screen, change
	// the compatible string to "nuvoton,ma35d1-adc",
	// For IIO-only ADC driver, use "nuvoton,ma35-adc" instead.
	compatible = "nuvoton,ma35d1-adc";

	reg = <0x0 0x40420000 0x0 0x500>;
	interrupts = <GIC_SPI 80 IRQ_TYPE_LEVEL_HIGH>;
	clocks = <&clk ADC_GATE>;
	clock-names = "adc_gate";
	clock-rate = <1000000>;

	// Properties for IIO-only ADC driver
	nuvoton,adc-vref = <3300>;
	nuvoton,min-clock-frequency = <3200000>;
	nuvoton,max-clock-frequency = <16000000>;
	#io-channel-cells = <1>;

	//Properties for hybrid ADC driver (IIO+TS)
	enable-iio;
	enable-ts;
	ts-type = <4>;

	status = "disabled";
};

in dts file;

adc0 {
	pinctrl_adc0: adc0grp {
		nuvoton,pins =
			//<SYS_GPB_MFPH_PB10MFP_ADC0_CH2	&pcfg_default>,
			//<SYS_GPB_MFPH_PB11MFP_ADC0_CH3	&pcfg_default>,
			<SYS_GPB_MFPH_PB12MFP_ADC0_CH4	&pcfg_default>, /* YM (Y-) - Y_B - Touch Bottom 	38 */
			<SYS_GPB_MFPH_PB13MFP_ADC0_CH5	&pcfg_default>, /* YP (Y+) - Y_T - Touch Top 		40 */
			<SYS_GPB_MFPH_PB14MFP_ADC0_CH6	&pcfg_default>, /* XM (X-) - X_L - Touch Left 		39 */
			<SYS_GPB_MFPH_PB15MFP_ADC0_CH7	&pcfg_default>; /* XP (X+) - X_R - Touch Right 		37 */
	};
};

I need to power the touchscreen with the ADC, but I'm not getting any response. Is there a faulty configuration? It works, albeit nonsensically, when I connect it to a different device, but there's no response with this one. What exactly is the correct configuration?

TFT screen this -> SAT043CM40DMY0-A0K-VSD-TP

[ychuang3]

clock-rate = <1000000>; ==> 200000

A 1 MHz clock is too high—it's recommended to lower it to 200 kHz and try again.

[TuAFBogey]

nothing has changed.

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1752644239.130605:    -89    273   5167
1752644239.138705:    -90    273   5172
1752644239.146801:    -89    272   5165
1752644239.154898:    -89    274   5173
1752644239.163000:    -90    275   5168
1752644239.171096:    -88    275   5174
1752644239.179195:    -88    275   5180
1752644239.187291:    -89    276   5174
1752644239.195391:    -88    278   5178
1752644239.203486:    -89    278   5171
1752644239.211585:    -90    278   5169
1752644239.219681:    -90    277   5179
1752644239.227781:    -89    278   5181
1752644239.235877:    -87    277   5185
1752644239.243976:    -89    276   5184
1752644239.252072:    -89    277   5187
1752644239.260171:    -89    277   5181
1752644239.268267:    -89    276   5171
1752644239.276366:    -89    276   5168
1752644239.284461:    -89    276   5182
1752644239.292556:    -89    277   5203
1752644239.300656:    -89    276   5227
1752644239.308752:    -86    275   5255
1752644239.316852:    -87    276   5261
1752644239.324947:    -85    275   5259
1752644239.333046:    -85    275   5283
1752644239.341142:    -86    274   5259
1752644239.349235:    -87    274   5259
1752644239.357336:    -87    274   5257
1752644239.365434:    -84    271   5343
1752644239.373537:    -84    269   5381
1752644239.381633:    -78    264   5464
1752644239.389732:    -75    258   5580
1752644239.397828:    -73    254   5659
1752644239.405927:    -65    246   5871
1752644239.414028:    -58    237   6085
1752644239.422123:    -52    229   6421
1752644239.430223:    -39    218   6828
1752644239.438318:    -43    209   6773
1752644239.446418:    -37    199   6979
1752644239.454514:    -40    192   6995
1752644239.462613:    -30    183   7201
1752644239.470713:    -29    173   7317
1752644239.478809:    -29    164   7331
1752644239.486908:    -30    154   7455
1752644239.495004:    -28    143   7666
1752644239.503104:    -24    134   7892
1752644239.511200:    -24    123   8093
1752644239.519299:    -26    106   8324
1752644239.527394:    -16    101   8948

when from the top left of the screen touch the corners first to the top right, then to the bottom right, then to the bottom left and then to the top left, and the values are like this. I did the calibration very precisely

[TuAFBogey]

I still haven't resolved this issue. Have you tested this?
When I touch the corners of the screen, the average coordinate values are as follows.

Location	X Value	Y value	Expected
Left Top	~26, -72	~122, 126	(0, 0)
Right Top	~437-512	~(-14) to 22	(480, 0)
Right Bottom	~442-456	~358-374	(480, 272)
Left Bottom	~159-186	~132-173	(0, 272)

	adc0: adc@40420000 {
		// To use hybrid ADC driver (IIO+TS) for touch screen, change
		// the compatible string to "nuvoton,ma35d1-adc",
		// For IIO-only ADC driver, use "nuvoton,ma35-adc" instead.
		compatible = "nuvoton,ma35d1-adc";

		reg = <0x0 0x40420000 0x0 0x10000>;
		interrupts = <GIC_SPI 80 IRQ_TYPE_LEVEL_HIGH>;
		clocks = <&clk ADC_GATE>;
		clock-names = "adc_gate";
		clock-rate = <200000>;

		// Properties for IIO-only ADC driver
		nuvoton,adc-vref = <3300>;
		nuvoton,min-clock-frequency = <3200000>;
		nuvoton,max-clock-frequency = <16000000>;
		#io-channel-cells = <1>;

		//Properties for hybrid ADC driver (IIO+TS)
		enable-iio;
		enable-ts;
		ts-type = <4>;

		status = "okay";
	};

&adc0 {
    status = "okay";
    pinctrl-names = "default";
    pinctrl-0 = <&pinctrl_adc0>;
};

adc0 {
	pinctrl_adc0: adc0grp {
		nuvoton,pins =
			/* <SYS_GPB_MFPH_PB10MFP_ADC0_CH2	&pcfg_default>, */
			/* <SYS_GPB_MFPH_PB11MFP_ADC0_CH3	&pcfg_default>, */
			<SYS_GPB_MFPH_PB12MFP_ADC0_CH4	&pcfg_default>, /* YM (Y-) - Y_B - Touch Bottom 	38 */
			<SYS_GPB_MFPH_PB13MFP_ADC0_CH5	&pcfg_default>, /* YP (Y+) - Y_T - Touch Top 		40 */
			<SYS_GPB_MFPH_PB14MFP_ADC0_CH6	&pcfg_default>, /* XM (X-) - X_L - Touch Left 		39 */
			<SYS_GPB_MFPH_PB15MFP_ADC0_CH7	&pcfg_default>; /* XP (X+) - X_R - Touch Right 		37 */
	};
};

/* Display Controller */
&display {
    status = "okay";
    pinctrl-names = "default";
    pinctrl-0 = <&pinctrl_lcm>;
    memory-region = <&display_buf>;
    
    nuvoton,sys = <&sys>;
    nuvoton,clk = <&clk>;
    clocks = <&clk DCU_GATE>, <&clk DCUP_DIV>;
    clock-names = "dcu_gate", "dcup_div";
    resets = <&reset MA35D1_RESET_DISP>;
    
    /* CRITICAL - Framebuffer console disable */
    reset_offset_en = "no";
    bits-per-pixel = <32>;
    pixel-fmt = <4>;
    swizzle = <0>;
    dpi-config = <0>;
    bus-width = <32>;
    
    buffer-num = <3>;
    colorkey-en = <1>;  /* Colorkey disable */
    overlay-en = <0>;   /* Overlay disable  */
    
    /* for cursor crash */
    enable-console = <0>;
    
    display-timings {
        native-mode = <&timing_480x272>;
        
        timing_480x272: sat043hs40dmy0 {
            clock-frequency = <8500000>;
            hactive = <480>;
            vactive = <272>;
            hsync-len = <41>;
            hfront-porch = <2>;
            hback-porch = <2>;
            vsync-len = <10>;
            vfront-porch = <2>;
            vback-porch = <2>;
            hsync-active = <0>;
            vsync-active = <0>;
        };
    };
};

[yclu-ntc]

Hi,
The DTS looks fine and the ADC is functioning correctly.
This situation seems more like instability during value calibration.
You can try the following:

1. Increase the pen-down duration during calibration.
2. Lower the ADC clock to improve stability. For example, try 100 MHz.

[TuAFBogey]

I reduced the speed to 25kHz.

ts-pressure-threshold = <100>;
ts-convert-time = <300>;

I added these two parameters to the dts file.

In the /etc/ts.conf file

# stability configuration
module_raw input
# sensitive pressure threshold
module pthres pmin=0
# Heavy dejittering for smooth movement
module dejitter delta=50
# Additional variance filtering
module variance delta=15
# Heavy median filtering for stability
module median depth=7
# Light smoothing
module iir N=8 D=10
# Linear calibration (from ts_calibrate)
module linear

I entered these settings.

The touchscreen is currently satisfactory. However, I have two problems.
1- Touch is only detected with fingernails or thin-tipped objects. It needs to be detected with a finger.
2- The ADC loading process during boot takes a long time. I think this is because I lowered the clock speed to 25kHz.

Do you have any suggestions on this?
Could there be a problem with the circuit connection? The display is connected directly to the ADC channels.

[yclu-ntc]

1. This phenomenon usually occurs with larger panels, indicating that the panel’s resistance is approaching the ADC’s input impedance limit. Lowering the ADC clock can stabilize the readings, but it may also result in requiring significantly more pressure to trigger a pen-down event.

2. This sounds a bit unusual, adjusting the ADC clock should not affect the probe speed of the ADC module during initialization. It’s possible that parameters in ts.conf are causing tslib to repeatedly read values during startup (maybe for filter purpose). Since a lower ADC clock increases the conversion time, this could lead to longer initialization times.

Therefore, you may need to experiment with an external resistor in order to achieve an optimal impedance match.