版权声明:本文为博主原创文章,遵循 CC 4.0 BY-SA 版权协议,转载请附上原文出处链接和本声明。
最近搞项目使用了EFM32这款单片机,感觉硬件I2C还是不够灵活,这次改成了模拟I2C方式通讯。
需要创建两个文件:i2c.h和i2c.c
以下是i2c.h文件实例代码:
#ifndef __IIC_H
#define __IIC_H
#include <stdint.h>
void i2c_read(uint8_t addr, uint8_t reg, uint8_t* buf, uint32_t len);
void i2c_write(uint8_t addr, uint8_t reg, uint8_t* buf, uint32_t len);
以下是i2c.c文件实例代码:
#include "i2c.h"
#include <stdint.h>
#include "em_chip.h"
#include "em_cmu.h"
#include "em_gpio.h"
#define SCK_TIME 2
#define ACK_TIME 3
#define START_TIME 5
/* Using PA0 (SDA) and PA1 (SCL) */
#define gpio_direction_input(a) \
if(#a=="SDA") \
{ \
GPIO_PinModeSet(gpioPortA, 0, gpioModeInput, 1); \
}
#define gpio_direction_output(a,b) \
if(#a=="SDA") \
{ \
GPIO_PinModeSet(gpioPortA, 0, gpioModePushPull, b); \
} \
else if(#a=="SCL") \
{ \
GPIO_PinModeSet(gpioPortA, 1, gpioModePushPull, b); \
}
#define gpio_set_value(a,b) \
if(#a=="SDA") \
{ \
if(b==1) GPIO_PinOutSet(gpioPortA,0); \
else if(b==0) GPIO_PinOutClear(gpioPortA,0);\
} \
else if(#a=="SCL") \
{ \
if(b==1) GPIO_PinOutSet(gpioPortA,1); \
else if(b==0) GPIO_PinOutClear(gpioPortA,1);\
}\
#define SDA 0
#define SCL 1
static uint8_t gpio_get_value(uint8_t sd) { return GPIO_PinInGet(gpioPortA, 0); }
static void udelay(uint32_t t)
{
for(; t!=0; t--);
}
static void i2c_start(void)
{
gpio_direction_output(SDA, 1);
gpio_direction_output(SCL, 1);
udelay(SCK_TIME);
gpio_set_value(SDA, 0);
udelay(START_TIME);
gpio_set_value(SCL, 0);
}
static void i2c_stop(void)
{
udelay(SCK_TIME);
gpio_direction_output(SDA, 0);
gpio_set_value(SCL, 1);
udelay(SCK_TIME);
gpio_set_value(SDA, 1);
}
static uint8_t i2c_read_ack(void)
{
uint8_t r;
gpio_direction_input(SDA);
udelay(ACK_TIME);
gpio_set_value(SCL,1);
udelay(1);
r = gpio_get_value(SDA);
udelay(1);
gpio_set_value(SCL,0);
return r;
}
static void i2c_send_ack(void)
{
udelay(SCK_TIME);
gpio_direction_output(SDA, 1);
gpio_set_value(SCL,1);
udelay(SCK_TIME);
gpio_set_value(SCL,0);
}
static void i2c_write_byte(uint8_t b)
{
int i;
for (i=7; i>=0; i--) {
udelay(SCK_TIME);
gpio_direction_output(SDA, b & (1<<i));
udelay(SCK_TIME - 2);
gpio_set_value(SCL, 1);
udelay(SCK_TIME);
gpio_set_value(SCL, 0);
}
i2c_read_ack();
}
static uint8_t i2c_read_byte(void)
{
int i;
uint8_t r = 0;
gpio_direction_input(SDA);
for (i=7; i>=0; i--) {
udelay(SCK_TIME * 5);
gpio_set_value(SCL, 1);
r |= (gpio_get_value(SDA) << i);
udelay(SCK_TIME * 5);
gpio_set_value(SCL, 0);
}
i2c_send_ack();
return r;
}
void i2c_read(uint8_t addr, uint8_t reg,uint8_t* buf, uint32_t len)
{
uint8_t i,t;
i2c_start();
t = (addr << 1) | 0;
i2c_write_byte(t);
i2c_write_byte(reg);
i2c_start();
t = (addr << 1) | 1;
i2c_write_byte(t);
for (i=0; i<len; i++)
buf[i] = i2c_read_byte();
i2c_stop();
}
void i2c_write(uint8_t addr, uint8_t reg, uint8_t* buf, uint32_t len)
{
uint8_t i,t;
i2c_start();
t = (addr << 1) | 0;
i2c_write_byte(t);
i2c_write_byte(reg);
for (i=0; i<len; i++)
i2c_write_byte(buf[i]);
i2c_stop();
}
测试
测试案例:(注,我这里使用了MPU9250 9轴传感器)
void main(void)
{
uint8_t res = 0;
uint8_t buf[] = {0};
buf[0] = 0x22;
while(1)
{
i2c_write(MPU9250_ADDR,MPU_INTBP_CFG_REG, buf, 1);
delay_ms(1000);
i2c_read(MPU9250_ADDR,MPU_INTBP_CFG_REG,&res,1);
printf(" res : %d \r\n", res);
}
}