ラズパイ とある場所のとある elinux.orgに関するメモ
ラズパイ とある場所のとある elinux.orgに関するメモ
root@raspi-81:~/elinux.org# pwd /root/elinux.org
URLはこちらです
root@raspi-81:~/elinux.org# cat README.txt http://elinux.org/RPi_Low-level_peripherals#C
いろんなサンプルコードがあって、たとえば、Lチカのコードならば
>||
root@raspi-81:~/elinux.org# cat ledtest.c
//
// 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
#include
#include
#include
#include
#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+*1 &= ~(7<<(((g)%10)*3))
#define OUT_GPIO(g) *(gpio+*2 |= (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<
