Phatina at 10:48, 10 June 2012

2012-06-10T10:48:36Z

Turbo-Frambozenbier at 18:57, 18 February 2012

2012-02-18T18:57:18Z

Turbo-Frambozenbier: Rpi Datasheet 751 GPIO Registers

2012-02-18T18:43:25Z

Rpi Datasheet 751 GPIO Registers

Turbo-Frambozenbier: Created page with "Code Example

 //  How to access GPIO registers from C-code on the Raspberry-Pi //  Example program //  15-January-2012 //  Dom and Gert  // Access from ARM Running Linux  #d..."

2012-02-18T18:42:34Z

Created page with "Code Example <pre> // How to access GPIO registers from C-code on the Raspberry-Pi // Example program // 15-January-2012 // Dom and Gert // Access from ARM Running Linux #d..."

New page

Code Example
<pre>
// How to access GPIO registers from C-code on the Raspberry-Pi
// Example program
// 15-January-2012
// Dom and Gert

// Access from ARM Running Linux

#define BCM2708_PERI_BASE 0x20000000
#define GPIO_BASE (BCM2708_PERI_BASE + 0x200000) /* GPIO controller */

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <dirent.h>
#include <fcntl.h>
#include <assert.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <sys/stat.h>

#include <unistd.h>

#define PAGE_SIZE (4*1024)
#define BLOCK_SIZE (4*1024)

int mem_fd;
char *gpio_mem, *gpio_map;
char *spi0_mem, *spi0_map;

// I/O access
volatile unsigned *gpio;

// GPIO setup macros. Always use INP_GPIO(x) before using OUT_GPIO(x) or SET_GPIO_ALT(x,y)
#define INP_GPIO(g) *(gpio+((g)/10)) &= ~(7<<(((g)%10)*3))
#define OUT_GPIO(g) *(gpio+((g)/10)) |= (1<<(((g)%10)*3))
#define SET_GPIO_ALT(g,a) *(gpio+(((g)/10))) |= (((a)<=3?(a)+4:(a)==4?3:2)<<(((g)%10)*3))

#define GPIO_SET *(gpio+7) // sets bits which are 1 ignores bits which are 0
#define GPIO_CLR *(gpio+10) // clears bits which are 1 ignores bits which are 0

void setup_io();

int main(int argc, char **argv)
{ int g,rep;

// Set up gpi pointer for direct register access
setup_io();

// Switch GPIO 7..11 to output mode

* You are about to change the GPIO settings of your computer. *
* Mess this up and it will stop working! *
* It might be a good idea to 'sync' before running this program *
* so at least you still have your code changes written to the SD-card! *
// Set GPIO pins 7-11 to output
for (g=7; g<=11; g++)
{
INP_GPIO(g); // must use INP_GPIO before we can use OUT_GPIO
OUT_GPIO(g);
}

for (rep=0; rep<10; rep++)
{
for (g=7; g<=11; g++)
{
GPIO_SET = 1<<g;
sleep(1);
}
for (g=7; g<=11; g++)
{
GPIO_CLR = 1<<g;
sleep(1);
}
}

return 0;

} // main

//
// Set up a memory regions to access GPIO
//
void setup_io()
{

/* open /dev/mem */
if ((mem_fd = open("/dev/mem", O_RDWR|O_SYNC) ) < 0) {
printf("can't open /dev/mem \n");
exit (-1);
}

/* mmap GPIO */

// Allocate MAP block
if ((gpio_mem = malloc(BLOCK_SIZE + (PAGE_SIZE-1))) == NULL) {
printf("allocation error \n");
exit (-1);
}

// Make sure pointer is on 4K boundary
if ((unsigned long)gpio_mem % PAGE_SIZE)
gpio_mem += PAGE_SIZE - ((unsigned long)gpio_mem % PAGE_SIZE);

// Now map it
gpio_map = (unsigned char *)mmap(
(caddr_t)gpio_mem,
BLOCK_SIZE,
PROT_READ|PROT_WRITE,
MAP_SHARED|MAP_FIXED,
mem_fd,
GPIO_BASE
);

if ((long)gpio_map < 0) {
printf("mmap error %d\n", (int)gpio_map);
exit (-1);
}

// Always use volatile pointer!
gpio = (volatile unsigned *)gpio_map;

} // setup_io
</pre>

← Older revision		Revision as of 18:57, 18 February 2012
Line 132:		Line 132:
	} // setup_io		} // setup_io
	</pre>		</pre>
		+	<br><br>
		+	{{Template:Raspberry Pi}}

Rpi Datasheet 751 GPIO Registers - Revision history

Phatina at 10:48, 10 June 2012

Turbo-Frambozenbier at 18:57, 18 February 2012

Turbo-Frambozenbier: Rpi Datasheet 751 GPIO Registers

Turbo-Frambozenbier: Created page with "Code Example
// How to access GPIO registers from C-code on the Raspberry-Pi // Example program // 15-January-2012 // Dom and Gert // Access from ARM Running Linux #d..."

@@ Line 57: / Line 57: @@
-   * You are about to change the GPIO settings of your computer.          *
+   /* You are about to change the GPIO settings of your computer.          *
-  * Mess this up and it will stop working!                               *
+   * Mess this up and it will stop working!                               *
-  * It might be a good idea to 'sync' before running this program        *
+   * It might be a good idea to 'sync' before running this program        *
-  * so at least you still have your code changes written to the SD-card! *
+   * so at least you still have your code changes written to the SD-card! */
-   // Set GPIO pins 7-11 to output
    for (g=7; g<=11; g++)
+   {

@@ Line 1: / Line 1: @@
-Code Example
+'''Code Example<br>
 <pre>
 //  How to access GPIO registers from C-code on the Raspberry-Pi