gpio test

3 files changed, 125 insertions, 0 deletions

diff --git a/.gitignore b/.gitignore
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+test
diff --git a/Makefile b/Makefile
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+test: test.c
+	gcc -o test test.c
diff --git a/test.c b/test.c
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+//
+//  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