The NXP i.MX8M Mini CPU has five 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 8M Mini platforms
-
On the ConnectCore 8M Mini system-on-module:
-
Many of the i.MX8M Mini GPIOs 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 GPIO pins and their multiplexed functionality.
-
15 MCA GPIO pins are available (labeled MCA_IOx where x is the GPIO pin).
-
-
On the ConnectCore 8M Mini Development Kit, the expansion connectors allow direct access to some of the i.MX8M Mini 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 i.MX8M Mini GPIOs is automatically provided through the non-visible option CONFIG_GPIO_MXC
.
Kernel driver
The driver for the i.MX8M Mini GPIO is located at:
File | Description |
---|---|
i.MX8M Mini GPIO driver |
Device tree bindings and customization
The i.MX8M Mini GPIO device tree binding is documented at
Documentation/devicetree/bindings/gpio/fsl-imx-gpio.yaml
.
One GPIO controller is defined for each i.MX8M Mini GPIO port in the common i.MX8M Mini device tree file:
gpio1: gpio@30200000 {
compatible = "fsl,imx8mm-gpio", "fsl,imx35-gpio";
reg = <0x30200000 0x10000>;
interrupts = <GIC_SPI 64 IRQ_TYPE_LEVEL_HIGH>,
<GIC_SPI 65 IRQ_TYPE_LEVEL_HIGH>;
clocks = <&clk IMX8MM_CLK_GPIO1_ROOT>;
gpio-controller;
#gpio-cells = <2>;
interrupt-controller;
#interrupt-cells = <2>;
gpio-ranges = <&iomuxc 0 10 30>;
};
[...]
gpio5: gpio@30240000 {
compatible = "fsl,imx8mm-gpio", "fsl,imx35-gpio";
reg = <0x30240000 0x10000>;
interrupts = <GIC_SPI 72 IRQ_TYPE_LEVEL_HIGH>,
<GIC_SPI 73 IRQ_TYPE_LEVEL_HIGH>;
clocks = <&clk IMX8MM_CLK_GPIO5_ROOT>;
gpio-controller;
#gpio-cells = <2>;
interrupt-controller;
#interrupt-cells = <2>;
gpio-ranges = <&iomuxc 0 119 30>;
};
The ConnectCore 8M Mini device tree include file and the carrier board device tree files use the i.MX8M Mini GPIOs.
For example, on the ConnectCore 8M Mini, GPIO3_IO08 is used as the MCA interrupt line, and GPIO1_IO5 is used to activate internal circuitry during the MCA firmware update:
mca_cc8m: mca@63 {
compatible = "digi,mca-kl17";
reg = <0x63>;
interrupt-parent = <&gpio2>;
interrupts = <10 IRQ_TYPE_LEVEL_LOW>;
interrupt-controller;
#interrupt-cells = <2>;
fw-update-gpio = <&gpio1 5 GPIO_ACTIVE_LOW>;
pinctrl-names = "default";
pinctrl-0 = <&pinctrl_mca_cc8m>;
[...]
};
For example, on the ConnectCore 8M Mini Development Kit, GPIO5_IO3 is used to reset the PHY of ENET1 Ethernet interface:
&fec1 {
pinctrl-names = "default";
pinctrl-0 = <&pinctrl_fec1_gpio>,
<&pinctrl_fec1>;
phy-mode = "rgmii-id";
phy-handle = <ðphy0>;
digi,mdio-lt-supply = <®_1v8_ext>;
phy-supply = <®_3v3_eth0>;
phy-reset-gpios = <&gpio5 3 GPIO_ACTIVE_LOW>;
phy-reset-duration = <1>;
digi,phy-reset-in-suspend;
fsl,magic-packet;
status = "okay";
[...]
};
IOMUX configuration
You must configure the pads that are to be used as i.MX8M Mini 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 8M Mini example from above, mca_cc8m
node configures pinctrl_mca_cc8m
:
pinctrl_mca_cc8m: mcagrp {
fsl,pins = <
/* MCA_nINT */
MX8MM_IOMUXC_SD1_RESET_B_GPIO2_IO10 0x56
/* MCA_FW_UPDATE */
MX8MM_IOMUXC_GPIO1_IO05_GPIO1_IO5 0x16
>;
};
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 8M Mini Development Kit J46 expansion connector:
Pad Signal GPIO 3
GPIO1_IO10
GPIO1_IO10
4
GPIO1_IO15
GPIO1_IO15
5
GPIO1_IO11
GPIO1_IO11
7
GPIO1_IO13
GPIO1_IO13
9
GPIO1_IO14
GPIO1_IO14
-
On the ConnectCore 8M Mini Development Kit J48 expansion connector:
Pad Signal GPIO 5
EXP_I2C_IRQ_N
GPIO5_IO27
7
EXP_I2C_GPIO
GPIO5_IO26
-
User LED 3 is GPIO2_IO19
-
User button 2 is GPIO2_IO20
GPIO pads power domains
The i.MX8M Mini 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 8M Mini Development Kit schematics. For instance, on the ConnectCore 8M Mini Development Kit, signal
UART4_TX
comes from padUART4_TXD
of the ConnectCore 8M Mini SOM: -
Locate this pad on the IOMUX section of the ConnectCore 8M Mini Hardware Reference Manual. This table lists the associated GPIO of the pad, and the power domain it is on:
-
Locate the power domain (
VDD_UART
on the example) on the ConnectCore 8M Mini Development Kit 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 gpioget
, 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/userspace-api/gpio/sysfs.html. |
Detect GPIO ports
Use gpiodetect
to list the GPIO ports detected by the kernel:
# gpiodetect
gpiochip0 [gpio1] (32 lines)
gpiochip1 [gpio2] (32 lines)
gpiochip2 [gpio3] (32 lines)
gpiochip3 [gpio4] (32 lines)
gpiochip4 [gpio5] (32 lines)
gpiochip5 [mca-gpio] (19 lines)
gpiochip6 [spi2.0] (2 lines)
where:
-
Ports
gpio1
togpio5
are the i.MX8M Mini GPIO ports. -
Port
mca-gpio
is the MCA GPIO port. -
Port
spi2.0
is the external CAN controller on the ConnectCore 8M Mini Development Kit.
Information about a GPIO port
Use gpioinfo
to list the lines of a given port:
# gpioinfo gpio1
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 "rts" output active-high [used]
line 4: unnamed unused input active-high
line 5: unnamed "mca-fw-update" output active-high [used]
line 6: unnamed "regulators:regulator@4" output active-high [used]
line 7: unnamed unused output active-high
line 8: unnamed unused output 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 output active-high
line 13: unnamed unused input active-high
line 14: unnamed unused input active-high
line 15: unnamed unused input active-high
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 unused input active-high
Set an output high/low
Use gpioset
to set a i.MX8M Mini GPIO as output, such as GPIO5_IO27.
Use =1
to set it high, or =0
to set it low:
# gpioset gpio5 27=1
# gpioset gpio5 27=0
Read an input
Use gpioget
to read the value of a i.MX8M Mini GPIO input, such as GPIO5_IO27:
# gpioget gpio5 27
0
Use a GPIO as interrupt
Use gpiomon
to wait for an event on a given GPIO, such as GPIO5_IO27:
# gpiomon --num-events 1 --rising-edge gpio5 27
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 the meta-digi layer.
This application shows how to manage GPIO lines using the Digi APIx library on the ConnectCore 8M Mini platform.
By default, the Get Started with ConnectCore Cloud Services demo application seizes the user button.
To use the example, stop the
|
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.