GPIO Pins Control - HummingBoard Ripple/Pulse & i.MX8M Mini SOM
- Kareiman Fadly (Unlicensed)
- Yazan Shhady
To control on the GPIO pins:
The external GPIOs are available under the /sys/class/gpio folder in Linux.
To control on the GPIO pins you need to calculate the GPIO number XX (*) and run the commands below:
# Export GPIO XX
echo XX > /sys/class/gpio/export
# Set GPIO pin Direction
echo "out" > /sys/class/gpio/gpioXX/direction
or
echo "in" > /sys/class/gpio/gpioXX/direction
# Set the value of an output pin
echo 1 > /sys/class/gpio/gpioXX/value
or
echo 0 > /sys/class/gpio/gpioXX/value
# Get the value of an input pin
cat > /sys/class/gpio/gpioXX/value
# Unexport GPIO XX
echo XX > /sys/class/gpio/unexport(*) from the schematics you can find the name of the pin/pad (find the pad name of the imx8mm processor side) and from here pins-imx8mm.h can find the GPIO define name of the pin/pad with the GPIO option like (MX8MM_IOMUXC_SAI2_RXD0_GPIO4_IO23), then you can calculate the GPIO number XX
XX = linux gpio number = (gpio_bank - 1) * 32 + gpio_bit
Example: to calculate the GPIO number of mikroBus J8 [pin 2]
Pad Name: SAI2_RXD
Pin Define: MX8MM_IOMUXC_SAI2_RXD0_GPIO4_IO23
GPIO Bank= 4
GPIO bit = 23
XX = ( 4 - 1) * 32 + 23 = 119
Attached here the MikroBus schematics:
MikroBus Pin | Pad Name (SOM side) | GPIO name | Linux GPIO number |
J8 [pin 2] | SAI2_RXD | GPIO4_IO23 | 119 |
J8 [pin 3] | ECSPI2_SS0 | GPIO5_IO13 | 141 |
J8 [pin 4] | ECSPI2_SCLK | GPIO5_IO10 | 138 |
J8 [pin 5] | ECSPI2_MISO | GPIO5_IO12 | 140 |
J8 [pin 6] | ECSPI2_MOSI | GPIO5_IO11 | 139 |
J10 [pin 1] | UART3_CTS -> UART3_RXD | GPIO5_IO26 | 154 |
J10 [pin 2] | UART3_RTS -> UART3_TXD | GPIO5_IO27 | 155 |
J10 [pin 3] | UART3_RXD -> UART1_RXD | GPIO5_IO22 | 150 |
J10 [pin 4] | UART3_TXD -> UART1_TXD | GPIO5_IO23 | 151 |
J10 [pin 5] | I2C3_SCL | GPIO5_IO18 | 146 |
J10 [pin 6] | I2C3_SDA | GPIO5_IO19 | 147 |
Note: from here pins-imx8mm.h can find the all supported functions of the pin (IOMUX options), from the Define names of same PAD name
for example, this pad ECSPI2_SS0 can support 5 functions (UART RTC, UART CTS, SPI SS, GPIO, TPSMP_HDATA)
Define format MX8MM_IOMUX (for more information can see NXP documentations)
To use the SPI of the MikroBus you need to configure the SPI signals in the device tree & generate new Linux kernel + device tree
You can this repo to generate the kerenl -
https://github.com/SolidRun/linux-stable/tree/linux-5.4.y-imx8
Here can find the imx8mm device
You can see an example here - https://community.nxp.com/t5/i-MX-Processors/Problem-with-jedec-spi-nor-on-IMX8M-Mini-EVK/m-p/963020
Related pages
SolidRun Ltd.