The MCA has several pads that work as GPIOs. The number of GPIO pins depends on the firmware programmed on the MCA.
Kernel configuration
You can manage the MCA GPIO driver support through the following kernel configuration option:
-
Digi ConnectCore 6UL Micro Controller Assist GPIO support (CONFIG_GPIO_MCA_CC6UL)
This option is enabled as built-in on the default ConnectCore 6UL kernel configuration file.
Kernel driver
The MCA GPIO driver is located at:
| File | Description |
|---|---|
ConnectCore 6UL MCA GPIO driver |
|
Common MCA GPIO driver |
Device tree bindings and customization
The MCA GPIO device tree binding is documented at Documentation/devicetree/bindings/gpio/gpio-mca-cc6ul.txt.
GPIO controller inside the MCA
mca_cc6ul: mca@7e {
...
mca_gpio: gpio {
compatible = "digi,mca-cc6ul-gpio";
gpio-controller;
#gpio-cells = <2>;
interrupt-parent = <&mca_cc6ul>;
interrupt-controller;
#interrupt-cells = <2>;
};
};Using the MCA GPIOs
The MCA GPIO driver works as any other GPIO driver of the kernel. You can access the MCA GPIOs from the sysfs. Refer to the Linux kernel documentation at Documentation/gpio/sysfs.txt.
The following table lists all available MCA IOs and their capabilities:
| MCA IO | PAD LGA/CS* | Digital I/O | IRQ-capable | ADC | 32KHz clock | 1.2 Vref |
|---|---|---|---|---|---|---|
MCA_IO0 |
A2/76 |
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MCA_IO1 |
B2 |
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MCA_IO2/EXT_VREF |
B5 |
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MCA_IO3 |
C3 |
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MCA_IO4 |
A3/75 |
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MCA_IO5 |
B6 |
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MCA_IO6/CLKOUT32K |
C4 |
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SWD_DIO/MCA_IO7 |
A7/71 |
|
* CS = castellated pads
Determine the GPIO controller
The system creates a sysfs entry for the MCA GPIO controller and assigns it a GPIO base number.
You can determine the MCA GPIO controller by reading the label for the different controller entries in /sys/class/gpio/.
~# ls /sys/class/gpio/ export gpiochip0 gpiochip128 gpiochip32 gpiochip504 gpiochip64 gpiochip96 unexport ~# cat /sys/class/gpio/gpiochip504/label mca-gpio
In this example, the MCA GPIO controller is /sys/class/gpio/gpiochip504.
Determine the number of GPIOs of the MCA
To determine the number of GPIO pins of the controller:
~# cat /sys/class/gpio/gpiochip504/ngpio 8
In this example, the MCA GPIO controller manages eight GPIOs.
MCA GPIO indexes
The number of the gpiochip controller shows Linux base number for the MCA GPIOs (504 in the example). You can also determine the base number with:
~# cat /sys/class/gpio/gpiochip504/base 504
This means that the MCA_IO0 pin corresponds to GPIO index 504 in Linux, MCA_IO1 corresponds to 505, and so on.
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Some of the MCA GPIO pins can be configured as ADC channels. When configured as ADC channel, a GPIO cannot be requested through the sysfs to be used as a standard GPIO. For information about configuring an MCA pin as ADC channel, see Analog-to-Digital Converter (ADC). |
