General Purpose Input/Output (GPIO)

The NXP {cpu-family} CPU has eight GPIO ports. Each port can generate and control 32 signals.

The MCA also features a number of GPIO pins (multiplexed with Analog-to-Digital Converter (ADC) functionality). See MCA I/O pads for a list of all available MCA IOs and their capabilities.

GPIOs on the ConnectCore 8X platforms

On the ConnectCore 8X system-on-module:
- Many, but not all, of the {cpu-family} GPIO ports and pins are available at the system-on-module, multiplexed with other functions (labeled GPIOx_IOy where x is the port and y is the GPIO pin). See Hardware reference manuals for information about what GPIO ports and pins are available and their multiplexed functionality.
- 19 MCA GPIO pins are available (labeled MCA_IOx where x is the GPIO pin).
On the ConnectCore 8X SBC Pro, the expansion connector allows direct access to several {cpu-family} GPIOs and MCA GPIOs.

GPIOs on the SOM and carrier board are used for many purposes, such as:

Power enable line for transceivers
Reset line for controllers
LCD backlight control
Interrupt line
User LED
User button

Kernel configuration

Support for {cpu-family} GPIOs is automatically provided through the non-visible option CONFIG_GPIO_MXC.

Kernel driver

The driver for the {cpu-family} GPIO is located at:

File Description

File	Description
`drivers/gpio/gpio-mxc.c`	{cpu-family} GPIO driver

drivers/gpio/gpio-mxc.c

{cpu-family} GPIO driver

Device tree bindings and customization

The {cpu-family} GPIO device tree binding is documented at Documentation/devicetree/bindings/gpio/fsl-imx-gpio.txt.

One GPIO controller is defined for each {cpu-family} GPIO port in the common {cpu-family} device tree file:

{cpu-family} device tree

	gpio0: gpio@5d080000 {
		compatible = "fsl,imx8qm-gpio", "fsl,imx35-gpio";
		reg = <0x0 0x5d080000 0x0 0x10000>;
		interrupts = <GIC_SPI 136 IRQ_TYPE_LEVEL_HIGH>;
		gpio-controller;
		#gpio-cells = <2>;
		power-domains = <&pd_lsio_gpio0>;
		interrupt-controller;
		#interrupt-cells = <2>;
	};

[...]

	gpio7: gpio@5d0f0000 {
		compatible = "fsl,imx8qm-gpio", "fsl,imx35-gpio";
		reg = <0x0 0x5d0f0000 0x0 0x10000>;
		interrupts = <GIC_SPI 143 IRQ_TYPE_LEVEL_HIGH>;
		gpio-controller;
		#gpio-cells = <2>;
		power-domains = <&pd_lsio_gpio7>;
		interrupt-controller;
		#interrupt-cells = <2>;
	};

The ConnectCore 8X device tree include file and the carrier board device tree files use the {cpu-family} GPIOs.

For example, on the ConnectCore 8X, GPIO3_IO09 is used to activate internal circuitry during the MCA firmware update:

ConnectCore 8X device tree

	mca_cc8x: mca@63 {
		compatible = "digi,mca-cc8x";
		reg = <0x63>;
		interrupt-parent = <&wu>;
		interrupts = <GIC_SPI 177 IRQ_TYPE_LEVEL_HIGH>;
		interrupt-controller;
		#interrupt-cells = <2>;
		fw-update-gpio = <&gpio3 9 GPIO_ACTIVE_LOW>;
		pinctrl-names = "default";
		pinctrl-0 = <&pinctrl_mca_cc8x>;

		[...]
};

For example, on the ConnectCore 8X SBC Pro, GPIO3_IO18 is used to reset the PHY of ENET1 Ethernet interface:

ConnectCore 8X SBC Pro device tree

&fec1 {
	pinctrl-names = "default";
	pinctrl-0 = <&pinctrl_fec_mdio>,
		    <&pinctrl_fec_gpio>,
		    <&pinctrl_fec1_gpio>,
		    <&pinctrl_fec1>;
	clocks = <&clk IMX8QXP_ENET0_IPG_CLK>,
		 <&clk IMX8QXP_ENET0_AHB_CLK>,
		 <&clk IMX8QXP_ENET0_REF_50MHZ_CLK>,
		 <&clk IMX8QXP_ENET0_PTP_CLK>,
		 <&clk IMX8QXP_ENET0_TX_CLK>;
	phy-mode = "rgmii-id";
	phy-handle = <&ethphy1>;
	phy-supply = <&reg_3v3_eth0>;
	phy-reset-gpios = <&gpio3 18 GPIO_ACTIVE_LOW>;
	phy-reset-duration = <1>;
	fsl,magic-packet;

	[...]
};

IOMUX configuration

You must configure the pads that are to be used as {cpu-family} GPIOs. See Pin multiplexing (IOMUX).

For GPIOs that are managed by other drivers, you must configure their pad IOMUX inside the driver node specific pinctrl-0 to work according to the specified interface functionalities.

On the ConnectCore 8X example from above, mca_cc8x node configures pinctrl_mca_cc8x:

ConnectCore 8X device tree

pinctrl_mca_cc8x: mcagrp {
	fsl,pins = <
		[...]

		/* MCA_FW_UPDATE */
		SC_P_QSPI0A_DATA0_LSIO_GPIO3_IO09	0x06000021
	>;
};

For GPIOs that are not associated with any interface or that can’t be handled by a driver, see Configure independent pin IOMUX and pad control. The following external pads are configured as GPIOs on the default device tree:

On the ConnectCore 8X SBC Pro expansion connector:

Pad	Signal	GPIO
A7	GPIO4_21	GPIO4_IO21
B7	GPIO4_20	GPIO4_IO20
C4	SPI0_IRQ_N	GPIO1_IO01
C7	EXP_I2C_IRQ_N	GPIO3_IO15
C8	EXP_I2C_GPIO	GPIO3_IO14
C13	ADC_IN4	GPIO1_IO14
C14	ADC_IN5	GPIO1_IO13
C15	GPIO4_19	GPIO4_IO19
C18	GPIO0_12	GPIO0_IO12
D11	M40_UART_TX	GPIO1_IO11
D12	M40_UART_RX	GPIO1_IO12
D14	ADC_IN1	GPIO1_IO09
D19	GPIO5_09	GPIO5_IO09

Pad

Signal

GPIO

GPIO4_21

GPIO4_IO21

GPIO4_20

GPIO4_IO20

SPI0_IRQ_N

GPIO1_IO01

EXP_I2C_IRQ_N

GPIO3_IO15

EXP_I2C_GPIO

GPIO3_IO14

C13

ADC_IN4

GPIO1_IO14

C14

ADC_IN5

GPIO1_IO13

C15

GPIO4_19

GPIO4_IO19

C18

GPIO0_12

GPIO0_IO12

D11

M40_UART_TX

GPIO1_IO11

D12

M40_UART_RX

GPIO1_IO12

D14

ADC_IN1

GPIO1_IO09

D19

GPIO5_09

GPIO5_IO09

GPIO pads power domains

The {cpu-family} GPIOs are configurable and can work at 1.8 V or 3.3 V depending on the power domain of the pad they are on.

To determine the working voltage of a given GPIO:

Locate the pad of a given signal on the ConnectCore 8X SBC Pro schematics. For instance, on the ConnectCore 8X SBC Pro, signal GPIO5_09 comes from pad ENET0_REFCLK_125M_25M of the ConnectCore 8X SOM:
Locate this pad on the IMOUX section of the ConnectCore 8X Hardware Reference Manual. This table lists the associated GPIO of the pad, and the power domain it is on:
Locate the power domain (VDD_ENET0 on the example) on the ConnectCore 8X SBC Pro schematics. Here you can tell the voltage of the power domain:

Using the GPIOs

The package libgpiod (added by packagegroup-dey-core) provides a set of tools (such as gpioset, gpioget, etc.) for controlling the GPIOs from user space.

You can still control the GPIOs from the sysfs, but this ABI is not recommended. See https://www.kernel.org/doc/html/latest/admin-guide/gpio/sysfs.html.

Detect GPIO ports

Use gpiodetect to list the GPIO ports detected by the kernel:

# gpiodetect
gpiochip0 [gpio0] (32 lines)
gpiochip1 [gpio1] (32 lines)
gpiochip2 [gpio2] (32 lines)
gpiochip3 [gpio3] (32 lines)
gpiochip4 [gpio4] (32 lines)
gpiochip5 [gpio5] (32 lines)
gpiochip6 [58222000.gpio] (32 lines)
gpiochip7 [mca-gpio] (19 lines)

where:

Ports gpio0 to gpio5 are the {cpu-family} GPIO ports available on the ConnectCore 8X.
Port 58222000.gpio is the MIPI GPIO controller.
Port mca-gpio is the MCA GPIO port.

Information about a GPIO port

Use gpioinfo to list the lines of a given port:

# gpioinfo gpio0
gpiochip0 - 32 lines:
	line   0:      unnamed       unused   input  active-high
	line   1:      unnamed       unused   input  active-high
	line   2:      unnamed       unused   input  active-high
	line   3:      unnamed       unused   input  active-high
	line   4:      unnamed       unused   input  active-high
	line   5:      unnamed       unused   input  active-high
	line   6:      unnamed       unused   input  active-high
	line   7:      unnamed       unused   input  active-high
	line   8:      unnamed       unused   input  active-high
	line   9:      unnamed       unused   input  active-high
	line  10:      unnamed       unused   input  active-high
	line  11:      unnamed       unused   input  active-high
	line  12:      unnamed       unused   input  active-high
	line  13:      unnamed "5v_display"  output  active-high [used]
	line  14:      unnamed  "3v3_audio"  output  active-high [used]
	line  15:      unnamed "3v3_usb_hub" output active-high [used]
	line  16:      unnamed       unused   input  active-high
	line  17:      unnamed       unused   input  active-high
	line  18:      unnamed       unused   input  active-high
	line  19:      unnamed       unused   input  active-high
	line  20:      unnamed       unused   input  active-high
	line  21:      unnamed       unused   input  active-high
	line  22:      unnamed       unused   input  active-high
	line  23:      unnamed       unused   input  active-high
	line  24:      unnamed       unused   input  active-high
	line  25:      unnamed       unused   input  active-high
	line  26:      unnamed       unused   input  active-high
	line  27:      unnamed       unused   input  active-high
	line  28:      unnamed       unused   input  active-high
	line  29:      unnamed       unused   input  active-high
	line  30:      unnamed       unused   input  active-high
	line  31:      unnamed        "vcc"  output  active-high [used]

Set an output high/low

Use gpioset to set a {cpu-family} GPIO as output, such as GPIO4_IO21. Use =1 to set it high, or =0 to set it low:

# gpioset gpio4 21=1
# gpioset gpio4 21=0

Read an input

Use gpioget to read the value of a {cpu-family} GPIO input, such as GPIO4_IO21:

# gpioget gpio4 21
0

Use a GPIO as interrupt

Use gpiomon to wait for an event on a given GPIO, such as GPIO4_IO21:

# gpiomon --num-events 1 --rising-edge gpio4 21

See the README of libgpiod for more information on the usage of these tools.

Sample application

An example application called apix-gpio-example is included in the dey-examples-digiapix recipe (part of dey-examples package) of meta-digi layer. This application shows how to manage GPIO lines using the Digi APIx library on the ConnectCore 8X platform.

Go to GitHub to see the application instructions and source code.

See GPIO API for more information about the GPIO APIx.

See MCA General Purpose Input/Output (GPIO) for additional information on MCA GPIOs.