Custom web page for IO Monitoring etc

[SpiderKenny]

Hi I'm using Omega 2S+ at the centre of a new controller.
I'd like to create some custom web pages on the Omega such that I can see and control some GPIO pins, but I have no idea where to begin with the specifics.
(I mean I know how to write HTML, upload files to the Omeag etc, and I understand that the Omega is running uhttpd on /www. But I don't knwo how to access GPIO from within the html)
Is there a guide on how to access stuff like GPIO from within the webserver?

[crispyoz]

@SpiderKenny A simple method would be to write your pages in PHP and use the exec function to call fastgpio command to interact with the GPIO.

[crispyoz]

@SpiderKenny Another method is to access the GPIO as a file, which you can also do using PHP or other method, here is how I do it in C. Not all my code, but can't recall the original author to credit.

#define GPIO_MAIN_DIRECTORY "/sys/class/gpio/"
#define GPIO_ENABLE_FILE "/sys/class/gpio/export"
#define GPIO_DISABLE_FILE "/sys/class/gpio/unexport"
#define GPIO_MAX_NUMBER 30

static int gpio_list[GPIO_MAX_NUMBER] = {0};

int gpio_get(int gpio_number)
{
    FILE *fp;
    char filename[50];
    char str[3];
    int value;

    if (gpio_list[gpio_number] != 1) {
        return EXIT_FAILURE;
    }

    snprintf("%sgpio%d/value", 50, GPIO_MAIN_DIRECTORY, gpio_number);
 
    fp = fopen(filename, "r");
    if (fp == NULL) {
        return EXIT_FAILURE;
    }

    value = getc(fp);

    fclose(fp);

    return value - 48; /* 48 is the ascii-value for '0' */
}

int gpio_set_direction(int gpio_number, char in_or_out[])
{
    FILE *fp;
    char filename[50] = GPIO_MAIN_DIRECTORY;
    char str[3];

    if (gpio_list[gpio_number] != 1) {
        return EXIT_FAILURE;
    }
    
    snprintf("%sgpio%d/direction", 50, GPIO_MAIN_DIRECTORY, gpio_number);

    fp = fopen(filename, "w");
    if (fp == NULL) {
        return EXIT_FAILURE;
    }

    fprintf(fp, in_or_out);
    fclose(fp);
    return EXIT_SUCCESS;
}

int gpio_set(int gpio_number, int value)
{
    FILE *fp;
    char filename[50] = GPIO_MAIN_DIRECTORY;
    char str[3];

    if (gpio_list[gpio_number] != 1) {
        return EXIT_FAILURE;
    }

    if (value > 0) {
        value = 1;
    }

    snprintf("%sgpio%d/value", 50, GPIO_MAIN_DIRECTORY, gpio_number);    

    fp = fopen(filename, "w");
    if (fp == NULL) {
        return EXIT_FAILURE;
    }

    sprintf(str, "%d", value);
    fprintf(fp, str);
    fclose(fp);

    return EXIT_SUCCESS;
}

int gpio_open(int gpio_number)
{
    FILE *fp;
    const char filename[] = GPIO_ENABLE_FILE;
    char str[3];

    gpio_list[gpio_number] = 1;

    fp = fopen(filename, "w");
    if (fp == NULL) {
        return EXIT_FAILURE;
    }

    fprintf(fp, "%d", gpio_number);
    fclose(fp);

    return EXIT_SUCCESS;
}

int gpio_close(int gpio_number)
{
    FILE *fp;
    const char filename[] = GPIO_DISABLE_FILE;
    char str[3];

    fp = fopen(filename, "w");
    if (fp == NULL) {
        printf("Could not open %s\n", filename);
        return EXIT_FAILURE;
    }

    fprintf(fp, "%d", gpio_number);
    fclose(fp);
    return EXIT_SUCCESS;
}

int gpio_close_all()
{
    int i;
    for (i = 0; i < GPIO_MAX_NUMBER; i++) {
        if (gpio_list[i] == 1) {
            gpio_close(i);
            gpio_list[i] = 0;
        }
    }
    return EXIT_SUCCESS;
}

[SpiderKenny]

@crispyoz Thank you!
I've done a bit of PHP in the past too. I'll give it a try.

[SpiderKenny]

@crispyoz BTW, in my C/C++ programming I usef the fastgpio library which uses direct register access. It's very quick and lightweight for accessing GPIO.

[crispyoz]

@SpiderKenny Yes fastgpio is better but I showed code that uses the file system instead as I'm not sure of your level of experience and this method is easy to implement.