求教模拟I2C发数据，最后一位为1时波形异常

Alvanbai · 发表于 2017-4-5 13:00:16

本帖最后由 Alvanbai 于 2017-4-5 13:02 编辑

各位前辈好，请教一下。我用的模拟I2C，发送一个字节8bit的数据，发现只要最后一位数据为1，SDA就异常。最后一位为0的话是正常的，请教一下可能的原因，谢谢。

图中分别发送的是0xFE和0xFF黄线是SDA，红线是SDL。经过测试，发现规律只要是最后一位数据为1，波形就拉不下去。

0xFE

0xFF

驱动代码参考了这位前辈，感谢。http://www.openedv.com/posts/list/61112.htm
I2C.C
[mw_shl_code=c,true]/**
  ******************************************************************************
  * @file    IIC.c
  * @brief    simulation function
  * @CPU    STM32F10x
  * @compiler  Keil uVision V4.74
  * @author Alex.fang(china shenzhen)
  * @copyright GPL
  * @version V1.0.0
  * @date    02-Sept-2015
  ******************************************************************************
  * @attention
  */



GPIO_InitTypeDef  GPIO_InitStructure;

void IIC_Init(void)
{
      RCC_APB2PeriphClockCmd(IIC_RCC_APB2Periph_GPIOx, ENABLE);
      GPIO_InitStructure.GPIO_Pin = IIC_SDA_GPIO_Pin | IIC_SCL_GPIO_Pin;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT;//普通输出模式
  GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;//推挽输出  //推挽输出
      GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
      GPIO_Init(IIC_GPIOx, &GPIO_InitStructure);
      GPIO_SetBits(IIC_GPIOx,IIC_SDA_GPIO_Pin | IIC_SCL_GPIO_Pin);  //PB10,PB11 输出高
}


void SDA_OUT(void)
{
      GPIO_StructInit(&GPIO_InitStructure);
      GPIO_InitStructure.GPIO_Pin = IIC_SDA_GPIO_Pin;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT;//普通输出模式
  GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;//推挽输出  //推挽输出 //推挽输出
      GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
      GPIO_Init(IIC_GPIOx, &GPIO_InitStructure);
}


void SDA_IN(void)
{
      GPIO_StructInit(&GPIO_InitStructure);
      GPIO_InitStructure.GPIO_Pin = IIC_SDA_GPIO_Pin;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN;
  GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_DOWN;
      GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
      GPIO_Init(IIC_GPIOx, &GPIO_InitStructure);
}


unsigned char SDA_READ(void)
{
      return GPIO_ReadInputDataBit(IIC_GPIOx, IIC_SDA_GPIO_Pin);
}


void IIC_SDA_1(void)
{
      GPIO_SetBits(IIC_GPIOx, IIC_SDA_GPIO_Pin);
}


void IIC_SDA_0(void)
{
      GPIO_ResetBits(IIC_GPIOx, IIC_SDA_GPIO_Pin);
}


void IIC_SCL_1(void)
{
      GPIO_SetBits(IIC_GPIOx, IIC_SCL_GPIO_Pin);
}


void IIC_SCL_0(void)
{
      GPIO_ResetBits(IIC_GPIOx, IIC_SCL_GPIO_Pin);
}



void IIC_Start(void)
{
SDA_OUT();    //sda output
IIC_SDA_1();
IIC_SCL_1();
delay_us(4);
IIC_SDA_0(); //START:when CLK is high,DATA change form high to low
delay_us(4);
IIC_SCL_0(); //hold scl line, prepare to transmit data
}


void IIC_Stop(void)
{
SDA_OUT(); //sda output mode
IIC_SCL_0();
IIC_SDA_0();  //STOP:when CLK is high DATA change form low to high
delay_us(4);
IIC_SCL_1();
IIC_SDA_1();  //indicate transmit over
delay_us(4);
}


unsigned char IIC_Wait_Ack(void)
{
unsigned char ucErrTime = 0;
SDA_IN();    //set as input mode
IIC_SDA_1();
delay_us(1);
IIC_SCL_1();
delay_us(1);
while(SDA_READ())
{
      ucErrTime++;
      if(ucErrTime > 250)
      {
         IIC_Stop();
         return 1;
      }
}
IIC_SCL_0(); //release scl line
return 0;
}


void IIC_Ack(void)
{
IIC_SCL_0();
SDA_OUT();
IIC_SDA_0();
delay_us(2);
IIC_SCL_1();
delay_us(2);
IIC_SCL_0();
}


void IIC_NAck(void)
{
IIC_SCL_0();
SDA_OUT();
IIC_SDA_1();
delay_us(2);
IIC_SCL_1();
delay_us(2);
IIC_SCL_0();
}



void IIC_Send_Byte(unsigned char txd)
{
      unsigned char i;
      SDA_OUT();
      IIC_SCL_0();//push down scl  to start transmit data
      for(i = 0; i < 8; ++i)
      {
      if(txd & 0x80)
      {
            IIC_SDA_1();
      }
      else
      {
            IIC_SDA_0();
      }
      txd <<= 1;
      delay_us(2);
      IIC_SCL_1();
      delay_us(2);
      IIC_SCL_0();
      delay_us(2);
      }
}


unsigned char IIC_Read_Byte(unsigned char ack)
{
      unsigned char i, res = 0;
      SDA_IN();             //SDA input mode
      for(i = 0; i < 8; ++i ){
            IIC_SCL_0();
            delay_us(2);
            IIC_SCL_1();
            res <<= 1;
            if(SDA_READ()){
                     res++;
            }
            delay_us(1);
      }
      if (!ack){
            IIC_NAck();//make NACK
      }
      else {
            IIC_Ack(); //make ACK
      }
      return res;
}  [/mw_shl_code]

I2C.H
[mw_shl_code=c,true]#define IIC_SDA_GPIO_Pin          GPIO_Pin_12
#define IIC_SCL_GPIO_Pin          GPIO_Pin_15
#define IIC_GPIOx                GPIOB
#define IIC_RCC_APB2Periph_GPIOx RCC_AHBPeriph_GPIOB

void IIC_Init(void);

void SDA_OUT(void);

void SDA_IN(void);

unsigned char SDA_READ(void);

void IIC_SDA_1(void);

void IIC_SDA_0(void);

void IIC_SCL_1(void);

void IIC_SCL_0(void);

void IIC_Start(void);

void IIC_Stop(void);

unsigned char IIC_Wait_Ack(void);

void IIC_Ack(void);

void IIC_NAck(void);

void IIC_Send_Byte(unsigned char txd);

unsigned char IIC_Read_Byte(unsigned char ack);

#endif[/mw_shl_code]