模拟IIC管脚电压低

ziyan0005 · 发表于 2018-4-4 15:47:02

本帖最后由 ziyan0005 于 2018-4-4 17:08 编辑

用STM32F103C8T6两个能容忍5V的管脚做IIC，10k上拉5V，做了一批板子，现在发现一个板子的SCL达不到4.5V，SDA能达到5V，请问什么问题？
SCL偶尔能到5V，大部分时间量都达不到4.5V，会是芯片管脚的问题吗？坏了？？

xyl210xyl · 发表于 2018-4-4 16:02:03

阻抗不对

ziyan0005 · 发表于 2018-4-4 16:38:07

xyl210xyl 发表于 2018-4-4 16:02
阻抗不对

SCL和SDA都是10k上拉

wxjhby · 发表于 2018-4-4 16:44:49

上拉电阻接小点 1.5K，2.2K，4.7K 选一种试试

ziyan0005 · 发表于 2018-4-4 16:51:51

wxjhby 发表于 2018-4-4 16:44
上拉电阻接小点 1.5K，2.2K，4.7K 选一种试试

那SDA能达到5V就不用换了呗？为什么同样的两个脚，同样的电阻值，电压就不一样了呢

正点原子 · 发表于 2018-4-5 01:26:23

ziyan0005 发表于 2018-4-4 16:51
那SDA能达到5V就不用换了呗？为什么同样的两个脚，同样的电阻值，电压就不一样了呢

看能不能通信，这是关键

xyl210xyl · 发表于 2018-4-8 09:06:39

ziyan0005 发表于 2018-4-4 16:38
SCL和SDA都是10k上拉

管脚配置看下

ziyan0005 · 发表于 2018-4-13 09:19:17

正点原子发表于 2018-4-5 01:26
看能不能通信，这是关键

能通信，可以正常用，就是电压低些

正点原子 · 发表于 2018-4-16 02:08:06

ziyan0005 发表于 2018-4-13 09:19
能通信，可以正常用，就是电压低些

设置开漏输出试试

ziyan0005 · 发表于 2018-5-3 15:36:49

正点原子发表于 2018-4-16 02:08
设置开漏输出试试

原子哥，IIC两个管脚是这样的
// I2C IO-Pins
// SDA on port B, bit 6
#define SDA1_LOW()  (GPIOB->BSRR = 0x00400000) // set SDA to low
#define SDA1_OPEN() (GPIOB->BSRR = 0x00000040) // set SDA to open-drain
#define SDA1_READ (GPIOB->IDR  & 0x0040)    // read SDA

// SCL on port B, bit 7
#define SCL1_LOW()  (GPIOB->BSRR = 0x00800000) // set SCL to low
#define SCL1_OPEN() (GPIOB->BSRR = 0x00000080) // set SCL to open-drain
#define SCL1_READ (GPIOB->IDR  & 0x0080)    // read SCL

etError I2c1_WriteByte(uint8 txByte)
{
  etError error = NO_ERROR;
  uint8    mask;
  for(mask = 0x80; mask > 0; mask >>= 1)// shift bit for masking (8 times)
  {
if((mask & txByte) == 0) SDA1_LOW(); // masking txByte, write bit to SDA-Line
else                   SDA1_OPEN();
DelayMicroSeconds(1);             // data set-up time (t_SU;DAT)
SCL1_OPEN();                      // generate clock pulse on SCL
DelayMicroSeconds(5);             // SCL high time (t_HIGH)
SCL1_LOW();
DelayMicroSeconds(1);             // data hold time(t_HD;DAT)
  }
SDA1_OPEN();                         // release SDA-line
  SCL1_OPEN();                         // clk #9 for ack

  DelayMicroSeconds(5);                // data set-up time (t_SU;DAT)
  if(SDA1_READ) error = ACK_ERROR;    // check ack from i2c slave
  SCL1_LOW();
  DelayMicroSeconds(20);             // wait to see byte package on scope
  return error;                      // return error code
}

//------------------------------------------------------------------------
uint8 I2c1_ReadByte(etI2cAck ack)
{
  uint8 mask;
  uint8 rxByte = NO_ERROR;
SDA1_OPEN();                         // release SDA-line
  for(mask = 0x80; mask > 0; mask >>= 1) // shift bit for masking (8 times)
  {
SCL1_OPEN();                         // start clock on SCL-line
DelayMicroSeconds(3);             // SCL high time (t_HIGH)
if(SDA1_READ) rxByte = rxByte | mask;       // read bit
SCL1_LOW();
DelayMicroSeconds(1);             // data hold time(t_HD;DAT)
  }
  if(ack == ACK) SDA1_LOW();             // send acknowledge if necessary
  else          SDA1_OPEN();

  DelayMicroSeconds(1);                // data set-up time (t_SU;DAT)
  SCL1_OPEN();                         // clk #9 for ack
  DelayMicroSeconds(5);                // SCL high time (t_HIGH)
  SCL1_LOW();
SDA1_OPEN();                         // release SDA-line
  DelayMicroSeconds(20);                // wait to see byte package on scope

  return rxByte;                         // return with no error
}

麻烦帮我看看，有错误吗？我今天遇到一个板子，这两个脚都是1V，我电路上上拉到5V

ziyan0005 · 发表于 2018-5-3 15:40:23

xyl210xyl 发表于 2018-4-8 09:06
管脚配置看下

IIC两个管脚是这样的
// I2C IO-Pins
// SDA on port B, bit 6
#define SDA1_LOW()  (GPIOB->BSRR = 0x00400000) // set SDA to low
#define SDA1_OPEN() (GPIOB->BSRR = 0x00000040) // set SDA to open-drain
#define SDA1_READ (GPIOB->IDR  & 0x0040)    // read SDA

// SCL on port B, bit 7
#define SCL1_LOW()  (GPIOB->BSRR = 0x00800000) // set SCL to low
#define SCL1_OPEN() (GPIOB->BSRR = 0x00000080) // set SCL to open-drain
#define SCL1_READ (GPIOB->IDR  & 0x0080)    // read SCL

etError I2c1_WriteByte(uint8 txByte)
{
  etError error = NO_ERROR;
  uint8    mask;
  for(mask = 0x80; mask > 0; mask >>= 1)// shift bit for masking (8 times)
  {
if((mask & txByte) == 0) SDA1_LOW(); // masking txByte, write bit to SDA-Line
else                   SDA1_OPEN();
DelayMicroSeconds(1);             // data set-up time (t_SU;DAT)
SCL1_OPEN();                      // generate clock pulse on SCL
DelayMicroSeconds(5);             // SCL high time (t_HIGH)
SCL1_LOW();
DelayMicroSeconds(1);             // data hold time(t_HD;DAT)
  }
      SDA1_OPEN();                         // release SDA-line
  SCL1_OPEN();                         // clk #9 for ack

  DelayMicroSeconds(5);                // data set-up time (t_SU;DAT)
  if(SDA1_READ) error = ACK_ERROR;    // check ack from i2c slave
  SCL1_LOW();
  DelayMicroSeconds(20);             // wait to see byte package on scope
  return error;                      // return error code
}

//------------------------------------------------------------------------
uint8 I2c1_ReadByte(etI2cAck ack)
{
  uint8 mask;
  uint8 rxByte = NO_ERROR;
      SDA1_OPEN();                         // release SDA-line
  for(mask = 0x80; mask > 0; mask >>= 1) // shift bit for masking (8 times)
  {
SCL1_OPEN();                         // start clock on SCL-line
DelayMicroSeconds(3);             // SCL high time (t_HIGH)
if(SDA1_READ) rxByte = rxByte | mask;       // read bit
SCL1_LOW();
DelayMicroSeconds(1);             // data hold time(t_HD;DAT)
  }
  if(ack == ACK) SDA1_LOW();             // send acknowledge if necessary
  else          SDA1_OPEN();

  DelayMicroSeconds(1);                // data set-up time (t_SU;DAT)
  SCL1_OPEN();                         // clk #9 for ack
  DelayMicroSeconds(5);                // SCL high time (t_HIGH)
  SCL1_LOW();
      SDA1_OPEN();                         // release SDA-line
  DelayMicroSeconds(20);                // wait to see byte package on scope

  return rxByte;                         // return with no error
}

麻烦帮我看看，有错误吗？我今天遇到一个板子，这两个脚都是1V，我电路上上拉到5V