通过/ dev / mem驱动Beaglebone GPIO [英] Driving Beaglebone GPIO through /dev/mem

问题描述

我正在为Beaglebone上的一个LED闪烁写一个C程序。我知道我可以使用sysfs方式...但是我想看看是否可以得到与/ dev / mem映射物理地址空间相同的结果。

  #ifndef _BEAGLEBONE_GPIO_H_ 
 #define _BEAGLEBONE_GPIO_H_ 
 
 #define GPIO1_START_ADDR 0x4804C000 
 #define GPIO1_END_ADDR 0x4804DFFF 
 #define GPIO1_SIZE（GPIO1_END_ADDR  -  GPIO1_START_ADDR）
 #define GPIO_OE 0x134 
 #define GPIO_SETDATAOUT 0x194 
 #define GPIO_CLEARDATAOUT 0x190 
 
 #define USR0_LED（1 <21）
 #define USR1_LED（1 <22）
 #define USR2_LED（1< ; 23）
 #define USR3_LED（1<< 24）
 
 #endif 
  

然后我有我的C程序，gpiotest.c

  #include< stdio.h> 
 #include< stdlib.h> 
 #include< sys / mman.h> 
 #include< sys / stat.h> 
 #include< fcntl.h> 
 #includebeaglebone_gpio.h
 
 int main（int argc，char * argv []）{
 volatile void * gpio_addr = NULL; 
 volatile unsigned int * gpio_oe_addr = NULL; 
 volatile unsigned int * gpio_setdataout_addr = NULL; 
 volatile unsigned int * gpio_cleardataout_addr = NULL; 
 unsigned int reg; 
 int fd = open（/ dev / mem，O_RDWR）; 
 
 printf（映射％X  - ％X（大小：％X）\\\
，GPIO1_START_ADDR，GPIO1_END_ADDR，GPIO1_SIZE）; 
 
 gpio_addr = mmap（0，GPIO1_SIZE，PROT_READ | PROT_WRITE，MAP_SHARED，fd，GPIO1_START_ADDR）; 
 
 gpio_oe_addr = gpio_addr + GPIO_OE; 
 gpio_setdataout_addr = gpio_addr + GPIO_SETDATAOUT; 
 gpio_cleardataout_addr = gpio_addr + GPIO_CLEARDATAOUT; 
 
 if（gpio_addr == MAP_FAILED）{
 printf（无法映射GPIO \）; 
 exit（1）; 
} 
 printf（GPIO映射到％p\\\
，gpio_addr）; 
 printf（GPIO OE映射到％p\\\
，gpio_oe_addr）; 
 printf（GPIO SETDATAOUTADDR映射到％p\\\
，gpio_setdataout_addr）; 
 printf（GPIO CLEARDATAOUT映射到％p\\\
，gpio_cleardataout_addr）; 
 
 reg = * gpio_oe_addr; 
 printf（GPIO1 configuration：％X\\\
，reg）; 
 reg = reg& （0xFFFFFFFF  -  USR1_LED）; 
 * gpio_oe_addr = reg; 
 printf（GPIO1 configuration：％X\\\
，reg）; 
 
 printf（开始闪烁LED USR1\\\
）; 
 while（1）{
 printf（ON\\\
）; 
 * gpio_setdataout_addr = USR1_LED; 
 sleep（1）; 
 printf（OFF\\\
）; 
 * gpio_cleardataout_addr = USR1_LED; 
 sleep（1）; 
} 
 
 close（fd）; 
 return 0; 
} 
  

输出是：

映射到4804C000 - 4804DFFF（大小：1FFF）
GPIO映射到0x40225000
GPIO OE映射到40225134
GPIO SEDATAOUTADDR映射到0x40225194
GPIO CLEARDATAOUTADDR映射到0x40225190
GPIO1配置：FE1FFFFF
GPIO1配置：FE1FFFFF
开始闪烁LED USR1
ON
OFF
ON
OFF
...

但我看不到LED闪烁。

从程序的输出可以看出，配置正确，FE1FFFFF，
是一致的，因为GPIO1_21，GPIO1_22，GPIO1_23和GPIO1_24被配置为输出
每个人驾驶一个LED。

任何关于原因的想法？

解决方案

修复是：

  pio_addr = mmap（0，GPIO1_SIZE，PROT_READ | PROT_WRITE，MAP_SHARED，fd，GPIO1_START_ADDR） 
  

I'm trying to write a C program for blinking a LED on the Beaglebone. I know I can use the sysfs way...but I'd like to see if it is possible to get the same result mapping the physical address space with /dev/mem.

I have a header file, beaglebone_gpio.h wit the following contents:

#ifndef _BEAGLEBONE_GPIO_H_
#define _BEAGLEBONE_GPIO_H_

#define GPIO1_START_ADDR 0x4804C000
#define GPIO1_END_ADDR 0x4804DFFF
#define GPIO1_SIZE (GPIO1_END_ADDR - GPIO1_START_ADDR)
#define GPIO_OE 0x134
#define GPIO_SETDATAOUT 0x194
#define GPIO_CLEARDATAOUT 0x190

#define USR0_LED (1<<21)
#define USR1_LED (1<<22)
#define USR2_LED (1<<23)
#define USR3_LED (1<<24)

#endif

and then I have my C program, gpiotest.c

#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <fcntl.h> 
#include "beaglebone_gpio.h"

int main(int argc, char *argv[]) {
    volatile void *gpio_addr = NULL;
    volatile unsigned int *gpio_oe_addr = NULL;
    volatile unsigned int *gpio_setdataout_addr = NULL;
    volatile unsigned int *gpio_cleardataout_addr = NULL;
    unsigned int reg;
    int fd = open("/dev/mem", O_RDWR);

    printf("Mapping %X - %X (size: %X)\n", GPIO1_START_ADDR, GPIO1_END_ADDR, GPIO1_SIZE);

    gpio_addr = mmap(0, GPIO1_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, GPIO1_START_ADDR);

    gpio_oe_addr = gpio_addr + GPIO_OE;
    gpio_setdataout_addr = gpio_addr + GPIO_SETDATAOUT;
    gpio_cleardataout_addr = gpio_addr + GPIO_CLEARDATAOUT;

    if(gpio_addr == MAP_FAILED) {
        printf("Unable to map GPIO\n");
        exit(1);
    }
    printf("GPIO mapped to %p\n", gpio_addr);
    printf("GPIO OE mapped to %p\n", gpio_oe_addr);
    printf("GPIO SETDATAOUTADDR mapped to %p\n", gpio_setdataout_addr);
    printf("GPIO CLEARDATAOUT mapped to %p\n", gpio_cleardataout_addr);

    reg = *gpio_oe_addr;
    printf("GPIO1 configuration: %X\n", reg);
    reg = reg & (0xFFFFFFFF - USR1_LED);
    *gpio_oe_addr = reg;
    printf("GPIO1 configuration: %X\n", reg);

    printf("Start blinking LED USR1\n");
    while(1) {
        printf("ON\n");
        *gpio_setdataout_addr= USR1_LED;
        sleep(1);
        printf("OFF\n");
        *gpio_cleardataout_addr = USR1_LED;
        sleep(1);
    }

    close(fd);
    return 0;
}

The output is:

Mapping 4804C000 - 4804DFFF (size: 1FFF)
GPIO mapped to 0x40225000
GPIO OE mapped to 40225134
GPIO SEDATAOUTADDR mapped to 0x40225194
GPIO CLEARDATAOUTADDR mapped to 0x40225190
GPIO1 configuration: FE1FFFFF
GPIO1 configuratino: FE1FFFFF
Start blinking LED USR1
ON
OFF
ON
OFF
...

but I can't see the led blinking.

As you can see from the output of the program the configuration is correct, FE1FFFFF, is coherent since GPIO1_21, GPIO1_22, GPIO1_23 and GPIO1_24 are configured as outputs, each one driving a LED.

Any idea about the reason?

解决方案

The fix is:

pio_addr = mmap(0, GPIO1_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, GPIO1_START_ADDR);

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