The NXP {cpu-family} 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 6UL platforms
-
On the ConnectCore 6UL system-on-module:
-
Many of the {cpu-family} 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.
-
Eight MCA GPIO pins are available (labeled MCA_IOx where x is the GPIO pin).
-
-
On the ConnectCore 6UL SBC Express, the expansion connector allows direct access to several {cpu-family} GPIOs and MCA GPIOs.
-
On the ConnectCore 6UL SBC Pro board, an I/O Expander chip features up to 39 GPIO pins (multiplexed with Analog-to-Digital Converter (ADC) functionality). See I/O Expander GPIO for additional information on I/O Expander GPIOs. The GPIO connector allows direct access to several {cpu-family} GPIOs, MCA GPIOs, and I/O Expander 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 |
---|---|
{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:
gpio1: gpio@0209c000 {
compatible = "fsl,imx6ul-gpio", "fsl,imx35-gpio";
reg = <0x0209c000 0x4000>;
interrupts = <GIC_SPI 66 IRQ_TYPE_LEVEL_HIGH>,
<GIC_SPI 67 IRQ_TYPE_LEVEL_HIGH>;
gpio-controller;
#gpio-cells = <2>;
interrupt-controller;
#interrupt-cells = <2>;
gpio-ranges = <&iomuxc 0 23 10>, <&iomuxc 10 17 6>,
<&iomuxc 16 33 16>;
};
[...]
gpio5: gpio@020ac000 {
compatible = "fsl,imx6ul-gpio", "fsl,imx35-gpio";
reg = <0x020ac000 0x4000>;
interrupts = <GIC_SPI 74 IRQ_TYPE_LEVEL_HIGH>,
<GIC_SPI 75 IRQ_TYPE_LEVEL_HIGH>;
gpio-controller;
#gpio-cells = <2>;
interrupt-controller;
#interrupt-cells = <2>;
gpio-ranges = <&iomuxc 0 7 10>, <&iomuxc 10 5 2>;
};
The ConnectCore 6UL device tree include file and the carrier board device tree files use the {cpu-family} GPIOs.
For example, on the ConnectCore 6UL, GPIO5_IO04 is used as interrupt line from the MCA, and GPIO4_IO14 is used to activate internal circuitry during the MCA firmware update:
mca_cc6ul: mca@7e {
compatible = "digi,mca-cc6ul";
reg = <0x7e>;
interrupt-parent = <&gpio5>;
interrupts = <4 IRQ_TYPE_EDGE_FALLING>;
interrupt-controller;
#interrupt-cells = <2>;
fw-update-gpio = <&gpio4 14 GPIO_ACTIVE_LOW>;
pinctrl-names = "default";
pinctrl-0 = <&pinctrl_mca_cc6ul>;
[...]
};
For example, on the ConnectCore 6UL SBC Pro, GPIO5_IO06 is used to reset the PHY of ENET2 Ethernet interface:
&fec2 {
pinctrl-names = "default";
pinctrl-0 = <&pinctrl_enet2>,
<&pinctrl_enet2_mdio>,
<&pinctrl_enet2_gpio>;
phy-mode = "rmii";
phy-handle = <ðphy1>;
phy-reset-gpios = <&gpio5 6 GPIO_ACTIVE_LOW>;
phy-reset-duration = <26>;
digi,phy-reset-in-suspend;
[...]
};
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 6UL example from above, mca_cc6ul
node configures pinctrl_mca_cc6ul
:
pinctrl_mca_cc6ul: mcagrp {
fsl,pins = <
/* MCA_nINT */
MX6UL_PAD_SNVS_TAMPER4__GPIO5_IO04 0xb0b1
/* MCA_FW_UPDATE */
MX6UL_PAD_NAND_CE1_B__GPIO4_IO14 0x30
>;
};
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 6UL SBC Express expansion connector:
Pad Signal GPIO 11
GPIO3_4
GPIO3_IO04
12
JTAG_TDI/GPIO1_13
GPIO1_IO13
13
GPIO3_10_PROT
GPIO3_IO10
15
JTAG_MOD/GPIO1_10
GPIO1_IO10
16
JTAG_TMS/GPIO1_11
GPIO1_IO11
18
GPIO3_12_PROT
GPIO3_IO12
27
PWM2/I2C3_SCL_PROT
GPIO3_IO06
29
GPIO5
GPIO1_IO05
32
PWM4_PROT
GPIO3_IO08
33
GPIO3_7/PWM3_PROT
GPIO3_IO07
35
JTAG_TDO/GPIO1_12
GPIO1_IO12
36
CSI_MCLK
GPIO4_IO17
37
CSI_PIXCLK
GPIO4_IO18
38
JTAG_nTRST/GPIO1_15
GPIO1_IO15
40
JTAG_TCK/GPIO1_14
GPIO1_IO14
-
On the ConnectCore 6UL SBC Pro GPIO connector:
Pad Signal GPIO 12
EXP_GPIO_2
GPIO1_IO03
SION bit
It is not possible to read the real signal level of a GPIO pin that is configured as an output. You can use the software input on (SION) bit to read the value of an output GPIO.
SION bit mode increases the power consumption of the module, so it is disabled by default. |
To enable the SION bit, set the bit 30 (special value). In other words, do an OR mask of your previous value with 0x40000000:
&iomuxc {
pinctrl-names = "default";
pinctrl-0 = <&pinctrl_hog>;
pinctrl_hog: hoggrp {
fsl,pins = <
/* GPIO3_IO04 on Expansion connector (SION enabled)*/
MX6UL_PAD_LCD_RESET__GPIO3_IO04 0x4000f030
>;
};
[...]
};
For more information, see the NXP Application Note AN5078.
Using the GPIOs
The package libgpiod (added by packagegroup-dey-core) provides a set of tools (gpioset
, gpioget
…) 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 [gpio1] (32 lines)
gpiochip1 [gpio2] (32 lines)
gpiochip2 [gpio3] (32 lines)
gpiochip3 [gpio4] (32 lines)
gpiochip4 [gpio5] (32 lines)
gpiochip5 [mca-gpio] (8 lines)
gpiochip6 [ioexp-gpio] (39 lines)
where:
-
Ports
gpio1
togpio5
are the {cpu-family} GPIO ports. -
Port
mca-gpio
is the MCA GPIO port. -
Port
ioexp-gpio
is the I/O Expander GPIO port.
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 unused input active-high
line 4: unnamed "usb_otg1_vbus" output active-high [used]
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 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 {cpu-family} 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 {cpu-family} 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 meta-digi layer.
This application shows how to manage GPIO lines using the Digi APIx library on the ConnectCore 6UL 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.
See I/O Expander for additional information on I/O Expander GPIOs.