【参考学习用】基于全志芯片的GPIO及底层（C/Python）编程 与 linux下/dev/mem分析
知乎上有一篇带例子的 Linux读写GPIO的几种方法及一些有趣的应用
曾经全志 A20 实现过 Python 操作 GPIO 的接口
http://dl.linux-sunxi.org/users/tom/pySUNXI-0.1.12.tar.gz
操作方法简单粗暴，直接怼到 /dev/mem 设备上用 mmap 映射 SUNXI_PIO_BASE 地址的操作，基于此还实现了 GPIO 模拟 SPI 设备。
gpio.c
/*
* gpio_lib.c
*
* Copyright 2013 Stefan Mavrodiev <support@olimex.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
* MA 02110-1301, USA.
*/
#include <ctype.h>
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <math.h>
#include <time.h>
#include <signal.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <sys/select.h>
#include <pthread.h>
#include <unistd.h>
#include <sched.h>
#include "gpio_lib.h"
unsigned int SUNXI_PIO_BASE = 0;
static volatile long int *gpio_map = NULL;
int sunxi_gpio_init(void) {
int fd;
unsigned int addr_start, addr_offset;
unsigned int PageSize, PageMask;
fd = open("/dev/mem", O_RDWR);
if(fd < 0) {
return SETUP_DEVMEM_FAIL;
}
PageSize = sysconf(_SC_PAGESIZE);
PageMask = (~(PageSize-1));
addr_start = SW_PORTC_IO_BASE & PageMask;
addr_offset = SW_PORTC_IO_BASE & ~PageMask;
gpio_map = (void *)mmap(0, PageSize*2, PROT_READ|PROT_WRITE, MAP_SHARED, fd, addr_start);
if(gpio_map == MAP_FAILED) {
return SETUP_MMAP_FAIL;
}
SUNXI_PIO_BASE = (unsigned int)gpio_map;
SUNXI_PIO_BASE += addr_offset;
close(fd);
return SETUP_OK;
}
int sunxi_gpio_set_cfgpin(unsigned int pin, unsigned int val) {
unsigned int cfg;
unsigned int bank = GPIO_BANK(pin);
unsigned int index = GPIO_CFG_INDEX(pin);
unsigned int offset = GPIO_CFG_OFFSET(pin);
if(SUNXI_PIO_BASE == 0) {
return -1;
}
struct sunxi_gpio *pio =
&((struct sunxi_gpio_reg *)SUNXI_PIO_BASE)->gpio_bank[bank];
cfg = *(&pio->cfg[0] + index);
cfg &= ~(0xf << offset);
cfg |= val << offset;
*(&pio->cfg[0] + index) = cfg;
return 0;
}
int sunxi_gpio_get_cfgpin(unsigned int pin) {
unsigned int cfg;
unsigned int bank = GPIO_BANK(pin);
unsigned int index = GPIO_CFG_INDEX(pin);
unsigned int offset = GPIO_CFG_OFFSET(pin);
if(SUNXI_PIO_BASE == 0)
{
return -1;
}
struct sunxi_gpio *pio = &((struct sunxi_gpio_reg *)SUNXI_PIO_BASE)->gpio_bank[bank];
cfg = *(&pio->cfg[0] + index);
cfg >>= offset;
return (cfg & 0xf);
}
int sunxi_gpio_output(unsigned int pin, unsigned int val) {
unsigned int bank = GPIO_BANK(pin);
unsigned int num = GPIO_NUM(pin);
if(SUNXI_PIO_BASE == 0)
{
return -1;
}
struct sunxi_gpio *pio =&((struct sunxi_gpio_reg *)SUNXI_PIO_BASE)->gpio_bank[bank];
if(val)
*(&pio->dat) |= 1 << num;
else
*(&pio->dat) &= ~(1 << num);
return 0;
}
int sunxi_gpio_input(unsigned int pin) {
unsigned int dat;
unsigned int bank = GPIO_BANK(pin);
unsigned int num = GPIO_NUM(pin);
if(SUNXI_PIO_BASE == 0)
{
return -1;
}
struct sunxi_gpio *pio =&((struct sunxi_gpio_reg *)SUNXI_PIO_BASE)->gpio_bank[bank];
dat = *(&pio->dat);
dat >>= num;
return (dat & 0x1);
}
void sunxi_gpio_cleanup(void)
{
unsigned int PageSize;
if (gpio_map == NULL)
return;
PageSize = sysconf(_SC_PAGESIZE);
munmap((void*)gpio_map, PageSize*2);
}
代码很有参考和学习的价值，看下文加深理解。
