CODEWITHSUNDEEP
clinuxtimerbeagleboard
Flavio Barisi
Flavio Barisi

Reputation: 470

Timer C programming on beagleboard-xm with armstrong

Good afternoon. My goal is writing a simple c program that run on my beagleboard-xm and open a led on gpio pin every 100 ms. I want to use timer interrupt to achive this. I'm trying to follow this tutorial

http://www.kunen.org/uC/beagle/omap_dmtimer.html

but i miss something. Do i need some kernel manipulation? I have installed native gcc compiler on beagleboard-xm and a cross compiler with Code Sourcery on windows 7 and i can build simple programs to manipulate leds, but both compiler don't recognize the headers used in the tutorial:

#include <linux/module.h>       
#include <linux/kernel.h>       
#include <linux/init.h>         
#include <linux/clk.h>      
#include <linux/irq.h>
#include <linux/interrupt.h>
#include <asm/io.h>         
#include <mach/dmtimer.h>   
#include <linux/types.h>

Any suggest will be much appreciated. Thanks in advance Here i post the code that I have used for GPIO manipulate

#include <stdio.h>
#include<signal.h>
#include<unistd.h>

void sig_handler(int signo) {
    if (signo == SIGINT) {
        FILE *fp;
        if ((fp = fopen("/sys/class/gpio/gpio157/direction", "w")) == NULL ) {
            exit(1);
        } else {
            fprintf(fp, "low");
            fclose(fp);
        }

        fp = fopen("/sys/class/gpio/unexport", "w");
        fprintf(fp, "157");
        fclose(fp);
        printf("Closing and cleaning \n");
    }

}

void main() {
    FILE *fp;

    printf("\n*************************************\n"
            "*  Welcome to PIN Blink program      *\n"
            "*  ....blinking pin 22 on port GPIO  *\n"
            "*  ....rate of 1 Hz............      *\n"
            "**************************************\n");

    if (signal(SIGINT, sig_handler) == SIG_ERR )
        printf("\ncan't catch SIGINT\n");

    fp = fopen("/sys/class/gpio/export", "w");
    fprintf(fp, "157");
    fclose(fp);

    printf("...export file accessed, new pin now accessible\n");

    while (1) {
        if ((fp = fopen("/sys/class/gpio/gpio157/direction", "w")) == NULL ) {
            printf("Error \n");
            exit(1);
        }
        fprintf(fp, "high");
        fclose(fp);
        sleep(1);

        if ((fp = fopen("/sys/class/gpio/gpio157/direction", "w")) == NULL ) {
            printf("Error \n");
            exit(1);
        }
        fprintf(fp, "low");
        fclose(fp);
        sleep(1);
    }

}

Upvotes: 4

Views: 3961

Answers (1)

Steve Lazaridis
Steve Lazaridis

Reputation: 2210

If you want to be able to manipulate the GPIO pins from userspace then you'll have to build a kernel driver/module to do that for you. And then you can send messages via ioctl,proc, or other kernel APIs to your driver to manipulate the GPIO pins.

The tutorial looks like a kernel driver example. You cannot build a regular user-space program with these headers. You'll need to either just build an example 'test driver' or do what I said above.

There are tons of resources online about kernel drivers. Here's one you should start with.

Linux Device Drivers, Third Edition

Upvotes: 1

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