摘要：
Fr=阿拉丁你可以清楚地看到百度百科。因此，起始地址应该是0x1000的整数倍。显然，0x01C20800需要减去0x800才能成为整数倍！如果｛printf；close；return；｝printf；//这里，0x1c20000的地址已映射到内存，但我们需要的地址是0x01C20800，因此我们需要添加地址偏移量~PIO=；输出函数关闭；//映射后可以关闭文件吗？“）；｝return0；｝gpio.h#ifndef_gpio_h__#define_gpio_h__#include＜studio.h＞#include＜unistd.h＞#include＜sys/mamman.h＞#include˂sys/types.h＞#incinclude＜sys/stat.h偏移值。-1的否定值为01，-2的否定值是01…gpio_SetPin；//usleep；sleep；｝gpio_Free（） ;} MakefileTARGET=myGPIO#可执行文件名########################编译参数######################
1.预备知识
https://baike.baidu.com/item/mmap/1322217?fr=aladdin 大家直接看百度百科，比较清楚了。
2.代码
gpio.c
#include "gpio.h" unsigned int fd; PIO_Map *PIO = NULL; unsigned int *gpio_map; unsigned int addr_start, addr_offset; unsigned int PageSize, PageMask; void GPIO_Init(void) { if ((fd = open("/dev/mem", O_RDWR)) == -1) { printf("open error "); return; } PageSize = sysconf(_SC_PAGESIZE); //使用sysconf查询系统页面大小 PageMask = (~(PageSize - 1)); //页掩码 printf("PageSize:%d,PageMask:0x%.8X ", PageSize, PageMask); addr_start = PIO_BASE_ADDRESS & PageMask; //0x01C20800 & 0xfffff000 = 0x1C20000 addr_offset = PIO_BASE_ADDRESS & ~PageMask; //0x01C20800 & 0x00000100 = 0x800 printf("addr_start:%.8X,addr_offset:0x%.8X ", addr_start, addr_offset); //mmap(系统自动分配内存地址，映射区长度“内存页的整数倍”，选择可读可写，MAP_SHARED=与其他所有映射到这个对象的进程共享空间，文件句柄，被映射内容的起点) //offest 映射物理内存的话，必须页对其!!! 所以这个起始地址应该是0x1000的整数倍，那么明显0x01C20800需要减去0x800才是整数倍！ if ((gpio_map = mmap(NULL, PageSize * 2, PROT_READ | PROT_WRITE, MAP_SHARED, fd, addr_start)) == NULL) { printf("mmap error "); close(fd); return; } printf("gpio_map:%.8X ", gpio_map); //这里已经将0x1c20000的地址映射到了内存中，但是我们需要的地址是0x01C20800，所以要再加上地址偏移量～ PIO = (PIO_Map *)((unsigned int)gpio_map + addr_offset); printf("PIO:0x%.8X ", PIO); close(fd); //映射好之后就可以关闭文件？ } void GPIO_ConfigPin(PORT port, unsigned int pin, PIN_MODE mode) { if (gpio_map == NULL) return; PIO->Pn[port].CFG[pin / 8] &= ~((unsigned int)0x07 << pin % 8 * 4); PIO->Pn[port].CFG[pin / 8] |= ((unsigned int)mode << pin % 8 * 4); printf("struct PIO_Struct size : %d",sizeof(PIO->Pn[port])); } void GPIO_SetPin(PORT port, unsigned int pin, unsigned int level) { if (gpio_map == NULL) return; if (level) PIO->Pn[port].DAT |= (1 << pin); else PIO->Pn[port].DAT &= ~(1 << pin); } int GPIO_Free(void) { if ((munmap(gpio_map, PageSize * 2)) == 0)//取消映射 { printf("unmap success! "); } else { printf("unmap failed! "); } return 0; }
gpio.h
#ifndef __GPIO_H__ #define __GPIO_H__ #include <stdio.h> #include <unistd.h> #include <sys/mman.h> #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #define PIO_BASE_ADDRESS 0x01C20800 //unsigned int 4字节 一个PIO_Struct占36字节,对应十六进制就是0x24，正好是一个offset值。 typedef struct { unsigned int CFG[4]; unsigned int DAT; unsigned int DRV0; unsigned int DRV1; unsigned int PUL0; unsigned int PUL1; } PIO_Struct; typedef struct { PIO_Struct Pn[7]; } PIO_Map; typedef enum { PA = 0, PB = 1, PC = 2, PD = 3, PE = 4, PF = 5, PG = 6, } PORT; typedef enum { IN = 0x00, OUT = 0x01, AUX = 0x02, INT = 0x06, DISABLE = 0x07, } PIN_MODE; extern PIO_Map *PIO; void GPIO_Init(void); void GPIO_ConfigPin(PORT port, unsigned int pin, PIN_MODE mode); void GPIO_SetPin(PORT port, unsigned int pin, unsigned int level); unsigned int GPIO_GetPin(PORT port, unsigned int pin); int GPIO_Free(void); #endif
main.c
#include <stdio.h> #include <unistd.h> #include <sys/mman.h> #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #include "gpio.h" #include <stdbool.h> int main() { int a=0,b=-1,i; GPIO_Init(); GPIO_ConfigPin(PB,4,OUT); GPIO_ConfigPin(PB,5,OUT); for(i=0;i<20;i++) { GPIO_SetPin(PB,4,a=~a);//！！-1的取反是0 1的取反是-2.... GPIO_SetPin(PB,5,b=~b); //usleep(100000); sleep(1); } GPIO_Free(); }
makefile
TARGET = myGPIO #可执行文件名称 ########################编译参数############################ CC = arm-linux-gnueabihf-gcc CXX = arm-linux-gnueabihf-g++ DEFINES = CFLAGS = -pipe -g -Wall -W -fPIE $(DEFINES) CXXFLAGS = -pipe -g -Wall -W -fPIE $(DEFINES) INCPATH = -I. ########################编译文件############################ SOURCES = ./main.c ./gpio.c OBJECTS = main.o gpio.o $(TARGET) : $(OBJECTS) $(CC) -o $(TARGET) $(OBJECTS) main.o : main.c gpio.h $(CC) $(include) $(CFLAGS) -c main.c gpio.o : gpio.c gpio.h $(CC) $(include) $(CFLAGS) -c gpio.c clean : rm $(OBJECTS) $(TARGET)
3.运行
将程序编译出来放到v3s上运行，那么pb4 pb5 会交替高低电平。