LED Blink in VisionTwo Board Using C Program

VisionFive 2 （English Forum)
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1

I am working on an LED blink program for the VisionFive 2 board using a C program. I have extensively referred to the following documents for guidance:

  1. https://starfivetech.com/uploads/Testing%20VisionFive%20GPIO.pdf
  2. https://wiki.rvspace.org/test-gpio.c

However, when execute this program on the board, I encountered the following error:

user@starfive:~$ ./gpio-debian 
********************************************
********  StarF_GPIO_TEST_DEMO  ************
********  Version date: 2021/12 ************
********************************************
Gpio begin to init
gpio/export: Permission denied
/sys/class/gpio/gpio470/direction: No such file or directory
Gpio init ok
/sys/class/gpio/gpio470/value: No such file or directory
Gpio off
/sys/class/gpio/gpio470/value: No such file or directory

I can successfully implemented the LED blink program in Python using the guide https://doc-en.rvspace.org/VisionFive2/PDF/Using_VisionFive_2_GPIO_to_Make_An_LED_Blink.pdf.

I m in need to achieve the same functionality in C program. please guide me. Thank you in advance

2

Solution
Install and Check GPIO Drivers
Navigate to the GPIO directory and ensure the GPIO drivers are working:

$ cd /sys/class/gpio/
$ ls
  export gpiochip0 gpiochip64 unexport
$ echo 44 > export
$ ls
  export gpio44 gpiochip0 gpiochip64 unexport
$ cd gpio44/
$ ls
  active_low direction subsystem value
$ cat direction
  in
$ cat value
  1
  1. Create LED Blinking C program - gpioLEDBlink.c 
    #include <stdio.h>
    #include <stdlib.h>
    #include <unistd.h>
    #include <string.h>
    #include <errno.h>
    #include <fcntl.h>
    #include <sys/stat.h>
    
    #define GPIO44 44
    #define FISCV_GPIO GPIO44
    #define MAX_BUF 128                      // Define array size
    #define StarF_Gpio_Dir "/sys/class/gpio" // GPIO control paths
    
    int StarF_gpio_export(unsigned int gpio) {
        int fd, len;
        char buf[MAX_BUF];
    
        // /sys/class/gpio/export
        fd = open("/sys/class/gpio/export", O_WRONLY);
        if (fd < 0) {
            perror("gpio/export");
            return fd;
        }
    
        len = snprintf(buf, sizeof(buf), "%d", gpio);
        write(fd, buf, len);
        close(fd);
    
        return 0;
    }
    
    int StarF_gpio_unexport(unsigned int gpio) {
        int fd, len;
        char buf[MAX_BUF];
    
        // /sys/class/gpio/unexport
        fd = open("/sys/class/gpio/unexport", O_WRONLY);
        if (fd < 0) {
            perror("gpio/unexport");
            return fd;
        }
    
        len = snprintf(buf, sizeof(buf), "%d", gpio);
        write(fd, buf, len);
        close(fd);
    
        return 0;
    }
    
    int StarF_gpio_set_dir(unsigned int gpio, unsigned int out_flag) {
        int fd, len;
        char buf[MAX_BUF];
    
        // /sys/class/gpio/gpioN/direction
        len = snprintf(buf, sizeof(buf), StarF_Gpio_Dir "/gpio%d/direction", gpio);
    
        fd = open(buf, O_WRONLY);
        if (fd < 0) {
            perror(buf);
            return fd;
        }
    
        if (out_flag) //'1' set to output
            write(fd, "out", 4);
        else // ‘0’ set input
            write(fd, "in", 3);
    
        close(fd);
        return 0;
    }
    
    int StarF_gpio_set_value(unsigned int gpio, unsigned int value) {
        int fd, len;
        char buf[MAX_BUF];
    
        // /sys/class/gpio/gpioN/value
        len = snprintf(buf, sizeof(buf), StarF_Gpio_Dir "/gpio%d/value", gpio);
        fd = open(buf, O_WRONLY);
        if (fd < 0) {
            perror(buf);
            return fd;
        }
    
        if (value) //'1' output is high level
            write(fd, "1", 2);
        else //'0' output is Low level
            write(fd, "0", 2);
    
        close(fd);
        return 0;
    }
    
    int StarF_gpio_get_value(unsigned int gpio, unsigned int *value) {
        int fd, len;
        char buf[MAX_BUF];
        char ch;
    
        // /sys/class/gpio/gpioN/value
        len = snprintf(buf, sizeof(buf), StarF_Gpio_Dir "/gpio%d/value", gpio);
    
        fd = open(buf, O_RDONLY);
        if (fd < 0) {
            perror("gpio/get-value");
            return fd;
        }
    
        read(fd, &ch, 1); // Read the external input level
    
        if (ch != '0') { //'1' Input is high level
            *value = 1;
        } else { //'0' Input is Low level
            *value = 0;
        }
    
        close(fd);
        return 0;
    }
    
    int main(int argc, char **argv) {
        unsigned int i;
        unsigned int value1, value2;
    
        printf("\t*************************************\n");
        printf("\t******** GPIO_LED_BLINK  ************\n");
        printf("\t*************************************\n");
        printf("Gpio begin to init\r\n");
        StarF_gpio_export(FISCV_GPIO); // export gpio Gpio
    
        StarF_gpio_set_dir(FISCV_GPIO, 1); // set as output
        printf("Gpio init ok\r\n");
    
        while (1) {
            StarF_gpio_set_value(FISCV_GPIO, 1); // output high
            printf("Gpio off\r\n");
            usleep(500000);                      // delay
            StarF_gpio_set_value(FISCV_GPIO, 0); // output low
            printf("Gpio on\r\n");
            usleep(500000); // delay
        }
    
        StarF_gpio_unexport(FISCV_GPIO); // unexport gpio Gpio
        return 0;
    }

  1. Compile and Run the Program

    $ gcc gpioLEDBlink.c -o gpioLEDBlink
    $ ./gpioLEDBlink

  2. Connect GPIO pin 40 to the positive terminal of the LED and link pin 6 (ground) to the LED’s negative terminal.

  3. This program initiates LED blinking at a 0.5-second interval.

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