I2C的两条线都是低电平，为何总线还是BUSY啊？

只看该作者 · 2011-5-17 09:45

本帖最后由 zddxmu 于 2011-5-18 09:19 编辑

官网例程如下
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void I2C_Init(void) {
  GPIOE->ODR |= 6;             //define SDA, SCL outputs, HiZ, Open drain, Fast
  GPIOE->DDR |= 6;
  GPIOE->CR2 |= 6;
#ifdef FAST_I2C_MODE
  I2C->FREQR = 16;             // input clock to I2C - 16MHz
  I2C->CCRL = 15;             // 900/62.5= 15, (SCLhi must be at least 600+300=900ns!)
  I2C->CCRH = 0x80;             // fast mode, duty 2/1 (bus speed 62.5*3*15~356kHz)
  I2C->TRISER = 5;             // 300/62.5 + 1= 5  (maximum 300ns)
#else
  I2C->FREQR = 8;             // input clock to I2C - 8MHz
  I2C->CCRL = 40;             // CCR= 40 - (SCLhi must be at least 4000+1000=5000ns!)
  I2C->CCRH = 0;                // standard mode, duty 1/1 bus speed 100kHz
  I2C->TRISER = 9;             // 1000ns/(125ns) + 1  (maximum 1000ns)
#endif
  I2C->OARL = 0xA0;             // own address A0;
  I2C->OARH |= 0x40;
  I2C->ITR = 1;                // enable error interrupts
  I2C->CR2 |= 0x04;             // ACK=1, Ack enable
  I2C->CR1 |= 0x01;             // PE=1
}

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官网例程有先设置GPIO，但为何是高电平输出呢？

我的程序因为SDA和SCL始终是高电平，总线一直busy。所以将GPIO设置成低电平输出，用万用表查出来是低电平，为什么总线还是处于BUSY呢？

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void I2C_init(void)
{
PB_ODR = 0x00;             //define SDA, SCL outputs, HiZ, Open drain, Fast
  PB_DDR |= 0x30;
  PB_CR2 |= 0x30;

  I2C_FREQR = 8;             // input clock to I2C - 8MHz
  I2C_CCRL = 40;             // CCR= 40 - (SCLhi must be at least 4000+1000=5000ns!)
  I2C_CCRH = 0;                // standard mode, duty 1/1 bus speed 100kHz
  I2C_TRISER = 9;             // 1000ns/(125ns) + 1  (maximum 1000ns)

  I2C_OARL = 0xA0;             // own address A0;
  I2C_OARH |= 0x40;
  I2C_ITR = 1;                // enable error interrupts
  I2C_CR2 |= 0x04;             // ACK=1, Ack enable
  I2C_CR1 |= 0x01;             // PE=1
I2C_CR2 &= 0x08;
}

只看该作者 · 2011-5-18 09:10

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