DESK-MX6UL-L/Peripherals/GPIOs

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History
Issue Date	Notes
2021/07/20	First DESK-MX6UL-L release
2022/03/16	DESK-MX6UL-L 3.0.0 release
2023/05/04	DESK-MX6UL-L 4.0.0 release
2024/08/07	DESK-MX6UL-L 4.2.x release

Peripheral GPIOs[edit | edit source]

i.MX6UL can handle external pins in many different ways and most of them can be configured as GPIOs. When a pin is set as a GPIO, it is possible to read its value, change its direction or change output value directly from the shell.

There aren't GPIOs configured in the AXEL ULite EVK

Here below an example of GPIOs usage in the i.MX6UL standard product RIALTO SBC

Device tree configuration[edit | edit source]

RIALTO SBC[edit | edit source]

Here below is an example of device tree configuration for using the:

RS-485 GPIOs
Relè
GPIO Push Button on Mezzanine Board
LEDs on Mezzanine Board

From imx6ul-lynx-som0022-cb0090.dts:

...
...
	leds {
		compatible = "gpio-leds";
		can_term {
			label = "can_term";
			gpios = <&gpio3 3 0>;
			default-state = "off";
		};

		uart2_en {
			label = "uart2_en";
			gpios = <&gpio1 22 0>;
			default-state = "on";
		};

		uart5_en {
			label = "uart5_en";
			gpios = <&gpio1 23 0>;
			default-state = "on";
		};
...
...
gpio-push-button {
		compatible = "gpio-keys";
		pinctrl-names = "default";
		pinctrl-0 = <&pinctrl_gpio_push_button>;
		status = "okay";
		f1 {
			label = "GPIO F1";
			gpios = <&gpio3 1 GPIO_ACTIVE_LOW>;
			linux,code = <KEY_F1>;
		};
	};

};
...
...

&i2c2 {
	status = "okay";
...
...
	pca9551@60 {
		pinctrl-names = "default";
		pinctrl-0 = <&pinctrl_pca60>;
		compatible = "nxp,pca9551";
		reg = <0x60>;
		#address-cells = <1>;
		#size-cells = <0>;
		reset-gpios = <&gpio3 22 GPIO_ACTIVE_LOW>;

		led@4 {
			label = "led2";
			reg = <4>;
			retain-state-shutdown;
			default-state = "keep";
			type = <PCA955X_TYPE_LED>;
		};

		led@5 {
			label = "led1";
			reg = <5>;
			retain-state-shutdown;
			default-state = "keep";
			type = <PCA955X_TYPE_LED>;
		};
	};
...
...
};
...
...
&iomuxc {
...
...
	imx6ul-lynx {
		pinctrl_hog_gpios: hoggrp-gpios {
			fsl,pins = <
				MX6UL_PAD_GPIO1_IO08__WDOG1_WDOG_B	0x0b0b1		/* WD RESET */
				MX6UL_PAD_GPIO1_IO01__GPIO1_IO01	0x1b0b1
				MX6UL_PAD_GPIO1_IO02__GPIO1_IO02	0x4001b0b1	/* Enable SION bit */
				MX6UL_PAD_GPIO1_IO03__GPIO1_IO03	0x4001b0b1	/* Enable SION bit */
				MX6UL_PAD_CSI_DATA04__GPIO4_IO25	0x1b0b1
				MX6UL_PAD_CSI_DATA05__GPIO4_IO26	0x1b0b1
				MX6UL_PAD_CSI_DATA06__GPIO4_IO27	0x1b0b1
				MX6UL_PAD_LCD_VSYNC__GPIO3_IO03		0x1b0b1 /* FlexCAN SW Termination */
				MX6UL_PAD_LCD_HSYNC__GPIO3_IO02		0x1b0b1 /* UART3 RS485 SW Termination */
				MX6UL_PAD_UART2_CTS_B__GPIO1_IO22	0x1b0b1 /* UART2 RS485 on RTIN enable */
				MX6UL_PAD_UART2_RTS_B__GPIO1_IO23	0x1b0b1 /* UART5 RS485 on RTIN enable */
			>;
		};

		pinctrl_gpio_push_button: gpio_push_button {
			fsl,pins = <
				MX6UL_PAD_LCD_RESET__GPIO3_IO04		0x1b0b0		/*KEY1*/
				MX6UL_PAD_LCD_ENABLE__GPIO3_IO01	0x1b0b0		/*KEY0*/
			>;
		};

...
...
};

Accessing the peripheral in RIALTO SBC[edit | edit source]

Using LEDs on Mezzanine Board[edit | edit source]

To blink LED1 on Mezzanine Board send the following commands

root@desk-mx6ul-rialto:~# echo 255 > /sys/class/leds/pca955x\:led1/brightness
root@desk-mx6ul-rialto:~# echo 0 > /sys/class/leds/pca955x\:led1/brightness
</pre>

To blink LED2 on Mezzanine Board send the following commands
<pre>
root@desk-mx6ul-rialto:~# echo 255 > /sys/class/leds/pca955x\:led2/brightness
root@desk-mx6ul-rialto:~# echo 0 > /sys/class/leds/pca955x\:led2/brightness

Using GPIO Push Button on Mezzanine Board[edit | edit source]

Pressing the Button generates the following event

root@desk-mx6ul-rialto:~# evtest /dev/input/event0
Input driver version is 1.0.1
Input device ID: bus 0x19 vendor 0x1 product 0x1 version 0x100
Input device name: "gpio-push-button"
Supported events:
  Event type 0 (EV_SYN)
  Event type 1 (EV_KEY)
    Event code 59 (KEY_F1)
Properties:
Testing ... (interrupt to exit)
[ 5332.805492] evbug: Event. Dev: input0, Type: 1, Code: 59, Value: 1
[ 5332.811800] evbug: Event. Dev: input0, Type: 0, Code: 0, Value: 0
Event: time 1651181469.356509, type 1 (EV_KEY), code 59 (KEY_F1), value 1
Event: time 1651181469.356509, -------------- SYN_REPORT ------------
[ 5333.103596] evbug: Event. Dev: input0, Type: 1, Code: 59, Value: 0
[ 5333.109908] evbug: Event. Dev: input0, Type: 0, Code: 0, Value: 0
Event: time 1651181469.654611, type 1 (EV_KEY), code 59 (KEY_F1), value 0
Event: time 1651181469.654611, -------------- SYN_REPORT ------------

Using Relé on RTIN add-on[edit | edit source]

set GPIO1_IO01 as output GPIO

GPIO1_IO01 => (n-1)*32 + IO = (1-1)*32+1 = 1

to enable and disable relè, with sysfs, use the command here below

root@desk-mx6ul-rialto:~# echo 1 > /sys/class/gpio/export
root@desk-mx6ul-rialto:~# echo out > /sys/class/gpio/gpio1/direction
root@desk-mx6ul-rialto:~# echo 1 > /sys/class/gpio/gpio1/value
root@desk-mx6ul-rialto:~# echo 0 > /sys/class/gpio/gpio1/value

to enable and disable relè, with libgpiod, use the command here below

root@desk-mx6ul-rialto:~# gpioset gpiochip0 1=1
root@desk-mx6ul-rialto:~# gpioset gpiochip0 1=0

set GPIO2_IO02 as output GPIO

GPIO2_IO02 => (n-1)*32 + IO = (1-1)*32+2 = 2

to enable and disable relè, with sysfs, use the command here below

root@desk-mx6ul-rialto:~# echo 2 > /sys/class/gpio/export
root@desk-mx6ul-rialto:~# echo out > /sys/class/gpio/gpio2/direction
root@desk-mx6ul-rialto:~# echo 1 > /sys/class/gpio/gpio2/value
root@desk-mx6ul-rialto:~# echo 0 > /sys/class/gpio/gpio2/value

to enable and disable relè, with libgpiod, use the command here below

root@desk-mx6ul-rialto:~# gpioset gpiochip0 2=1
root@desk-mx6ul-rialto:~# gpioset gpiochip0 2=0

Using INPUT GPIO on RTIN add-on[edit | edit source]

A loopback HW connection is wired between relè and INPUT GPIO for testing purposes: the relè output sets the INPUT GPIO value.

The relè as shown in the previous chapter is set and then the INPUT GPIOs value is read.

set GPIO4_IO26 as input GPIO

GPIO4_IO26 => (n-1)*32 + IO = (4-1)*32+26 = 122

to enable input GPIO, with sysfs, use the command here below

root@desk-mx6ul-rialto:~# echo 122 > /sys/class/gpio/export
root@desk-mx6ul-rialto:~# echo in > /sys/class/gpio/gpio122/direction
root@desk-mx6ul-rialto:~# cat /sys/class/gpio/gpio122/value
1

to read value of input GPIOs with libgpiod, use the command here below
```
root@desk-mx6ul-rialto:~# gpioget gpiochip3 26
1
```

set GPIO4_IO27 as input GPIO

GPIO4_IO27 => (n-1)*32 + IO = (4-1)*32+27 = 123

to enable input GPIO, with sysfs, use the command here below

root@desk-mx6ul-rialto:~# echo 123 > /sys/class/gpio/export
root@desk-mx6ul-rialto:~# echo in > /sys/class/gpio/gpio123/direction
root@desk-mx6ul-rialto:~# cat /sys/class/gpio/gpio123/value
1

to read value of input GPIOs with libgpiod, use the command here below
```
root@desk-mx6ul-rialto:~# gpioget gpiochip3 27
1
```

Additional information[edit | edit source]

Information about GPIOs usage under sysfs directory https://www.kernel.org/doc/Documentation/gpio/sysfs.txt

sysfs GPIO ABI has been deprecated. Please find more information here about it. A character device access has to be used, more information here

Information about GPIOs library libgpiod - C library and tools - can be found on git.kernel.org

HOME	SOMs	SBCs	ToloMEO Embedded Assistant	GET A QUOTE	ONLINE HELPDESK
	Roadmap		IoT Services			ML/AI services	Embedded Design Services

DESK-MX6UL-L/Peripherals/GPIOs

Contents

Peripheral GPIOs[edit | edit source]

Device tree configuration[edit | edit source]

RIALTO SBC[edit | edit source]

Accessing the peripheral in RIALTO SBC[edit | edit source]

Using LEDs on Mezzanine Board[edit | edit source]

Using GPIO Push Button on Mezzanine Board[edit | edit source]

Using Relé on RTIN add-on[edit | edit source]

Using INPUT GPIO on RTIN add-on[edit | edit source]

Additional information[edit | edit source]

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