I am using IVY Carrier board with iMX8M plus SOM, I did all development setup and also able to run the sample code using local docker setup.
The following GPIO toggle code i created to toggle LED on carrier board:
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/ioctl.h>
#include <linux/gpio.h>
int main() {
const char *chipname = "/dev/gpiochip2"; // GPIO chip device
int line = 25; // GPIO line number (adjust for your board)
int fd, ret;
printf("GPIO Example Started\n");
// Open GPIO chip
fd = open(chipname, O_RDONLY);
if (fd < 0) {
perror("Failed to open gpiochip device");
return EXIT_FAILURE;
}
// Request line
struct gpiohandle_request req;
memset(&req, 0, sizeof(req));
req.lineoffsets[0] = line; // which GPIO line
req.flags = GPIOHANDLE_REQUEST_OUTPUT; // request as output
req.lines = 1; // number of lines requested
req.default_values[0] = 0; // initial value (LOW)
strcpy(req.consumer_label, "my-gpio-app");
ret = ioctl(fd, GPIO_GET_LINEHANDLE_IOCTL, &req);
if (ret == -1) {
perror("Failed to request line");
close(fd);
return EXIT_FAILURE;
}
// Toggle GPIO value
struct gpiohandle_data data;
data.values[0] = 1; // set HIGH
ret = ioctl(req.fd, GPIOHANDLE_SET_LINE_VALUES_IOCTL, &data);
if (ret == -1) {
perror("Failed to set line value HIGH");
}
sleep(5);
data.values[0] = 0; // set LOW
ret = ioctl(req.fd, GPIOHANDLE_SET_LINE_VALUES_IOCTL, &data);
if (ret == -1) {
perror("Failed to set line value LOW");
}
sleep(5);
// Release line handle
close(req.fd);
close(fd);
printf("GPIO %d toggled successfully\n", line);
return EXIT_SUCCESS;
}
This code successfully compile and ran without ERRORs but not able to see the GPIO pin actually toggle.
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Hello Vishal,
Your code looks correct, but the issue is likely that the GPIO pin needs to be properly configured for GPIO functionality through the device tree. On i.MX 8M Plus based modules, pins need to be explicitly muxed to GPIO function before they can be used as GPIOs (1).
Pin Configuration Requirements
For i.MX 8M Plus based modules, you need to configure the pin multiplexing in the device tree (1). The pin control configuration requires defining a device tree node inside the pin controller node with the fsl,pins property (1).
Device Tree Configuration Steps
Create a custom device tree overlay to configure GPIO2_25 for GPIO functionality (2):
Identify the correct pin definition by checking the i.MX 8M Plus Applications Processor Reference Manual and the pin function definitions in imx8mp-pinfunc.h(1).
Pin Control Settings
The recommended pad configuration value 0x1c4 provides weak pull-up configuration (1). For GPIO applications, you can also use 0x184 for weak pull-down if needed (1).
Alternative Approach
If you only need to set the pin direction and don’t want to use gpio-hog in the device tree, you can configure just the pinmux in the overlay and then control the direction from your application (3). This approach requires:
Configure only the pinmux in the device tree overlay
Use your existing C code to control the GPIO direction and value
Verification Steps
After applying the device tree overlay:
Check if the GPIO is properly exported: ls /sys/class/gpio/
Verify the pin configuration with a multimeter or oscilloscope
Ensure no other peripherals are using the same pin
The key issue is that without proper device tree configuration, the pin remains in its default function and cannot be controlled as a GPIO (1).
Can you let me know which pin (SODIMM number) you are expecting the value change to be on? Can you validate this sodimm number to your gpiochip and line number?
Thanks @eric.tx for your suggestion to get correct me. Now If I used SODIMM 208 then it working as expected. If i want to modify device tree which steps i need to follow? As I am new in Linux could you please provide me reference tutorial step by step that i will execute from my side.
I want to blink Status LED that connected on IVY board.
We have our developer.toradex.com website if you are not familiar, we have quite a bit of guides, including a “first steps” with device trees. Here is the link.
For modifying the device tree for our linux based Torizon OS. I would actually mention something called device tree overlays, theses are device tree modifications that happen after boot. We have a tool we build called “torizoncore-builder” that allows for device tree overlays to be easily integrated into a customized Torizon OS.
This is the overview for the builder tool. And on the left you can see menu drop downs that will walk you through (1) Installing the tool (2) customizing the OS framework/source files (3) configuration files (where you can do Overlays.
