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| -rw-r--r-- | .gitignore | 1 | ||||
| -rw-r--r-- | Makefile | 2 | ||||
| -rw-r--r-- | test.c | 122 |
3 files changed, 125 insertions, 0 deletions
diff --git a/.gitignore b/.gitignore new file mode 100644 index 0000000..9daeafb --- /dev/null +++ b/.gitignore @@ -0,0 +1 @@ +test diff --git a/Makefile b/Makefile new file mode 100644 index 0000000..b85b5ab --- /dev/null +++ b/Makefile @@ -0,0 +1,2 @@ +test: test.c + gcc -o test test.c @@ -0,0 +1,122 @@ +// +// How to access GPIO registers from C-code on the Raspberry-Pi +// Example program +// 15-January-2012 +// Dom and Gert +// Revised: 15-Feb-2013 + + +// Access from ARM Running Linux + +#define BCM2708_PERI_BASE 0x20000000 +#define GPIO_BASE (BCM2708_PERI_BASE + 0x200000) /* GPIO controller */ + + +#include <stdio.h> +#include <stdlib.h> +#include <fcntl.h> +#include <sys/mman.h> +#include <unistd.h> + +#define PAGE_SIZE (4*1024) +#define BLOCK_SIZE (4*1024) + +int mem_fd; +void *gpio_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 + +#define GET_GPIO(g) (*(gpio+13)&(1<<g)) // 0 if LOW, (1<<g) if HIGH + +#define GPIO_PULL *(gpio+37) // Pull up/pull down +#define GPIO_PULLCLK0 *(gpio+38) // Pull up/pull down clock + +void setup_io(); + +void printButton(int g) +{ + if (GET_GPIO(g)) // !=0 <-> bit is 1 <- port is HIGH=3.3V + printf("Button pressed!\n"); + else // port is LOW=0V + printf("Button released!\n"); +} + +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); +// } + INP_GPIO(21); + OUT_GPIO(21); + + for (rep=0; rep>=0; rep++) + { + GPIO_SET = 1<<21; + GPIO_CLR = 1<<21; + } + + 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 */ + gpio_map = mmap( + NULL, //Any adddress in our space will do + BLOCK_SIZE, //Map length + PROT_READ|PROT_WRITE,// Enable reading & writting to mapped memory + MAP_SHARED, //Shared with other processes + mem_fd, //File to map + GPIO_BASE //Offset to GPIO peripheral + ); + + close(mem_fd); //No need to keep mem_fd open after mmap + + if (gpio_map == MAP_FAILED) { + printf("mmap error %d\n", (int)gpio_map);//errno also set! + exit(-1); + } + + // Always use volatile pointer! + gpio = (volatile unsigned *)gpio_map; + + +} // setup_io |