I2C Bus not pulsing after the start condition

[ngoclt]

Posted on October 31, 2012 at 21:57

I am communicating with a slave device and after the generation of the start condition, I am not seeing SCL and SDA pulsing. Below is the code: 

void DS2482_Init(void)

{

        GPIO_InitTypeDef    GPIO_InitStructure;

        I2C_InitTypeDef     I2C_InitStructure;

        

        /* Enable peripheral clock */

        RCC_APB1PeriphClockCmd(RCC_APB1Periph_I2C2, ENABLE);

        /* Enable GPIOB clock */

        RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB, ENABLE);

     

        /* Configure I2C2_SCL and I2C2_SDA */

        GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10;

        GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_OD;

        GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;

        GPIO_Init(GPIOB, &GPIO_InitStructure);

        

        GPIO_InitStructure.GPIO_Pin = GPIO_Pin_11;

        GPIO_Init(GPIOB, &GPIO_InitStructure);

        

        /* Enable I2C2 reset state */

        //RCC_APB1PeriphResetCmd(RCC_APB1Periph_I2C2, ENABLE);

        /* Release I2C2 from reset state */

        //RCC_APB1PeriphResetCmd(RCC_APB1Periph_I2C2, DISABLE);

                

        I2C_DeInit(DS2482_I2C);

        

        /* DS2482 peripheral configuration */

        I2C_InitStructure.I2C_Mode = I2C_Mode_I2C; 

        I2C_InitStructure.I2C_DutyCycle = I2C_DutyCycle_2;

        I2C_InitStructure.I2C_OwnAddress1 = DS2482_I2C_ADDRESS;

        I2C_InitStructure.I2C_Ack = I2C_Ack_Enable;

        I2C_InitStructure.I2C_AcknowledgedAddress = I2C_AcknowledgedAddress_7bit;

        I2C_InitStructure.I2C_ClockSpeed = DS2482_I2C_SPEED;

        /* enable the I2C peripheral */

        I2C_Cmd(DS2482_I2C, ENABLE);

        I2C_Init(DS2482_I2C, &I2C_InitStructure);       

}

int DS2482_channel_select(int channel)

{

    // select the 1-wire channel on DS2482-800

    // Returns: TRUE if channel selected

    //          FALSE if device not detected

    unsigned char ch, ch_read, check;

    

    /* while the bus is busy */

    while(I2C_GetFlagStatus(DS2482_I2C, I2C_FLAG_BUSY));

    

    /* send START condition */

    I2C_GenerateSTART(DS2482_I2C, ENABLE);

    

    /* test on EV5 and clear it */

    while(!I2C_CheckEvent(DS2482_I2C, I2C_EVENT_MASTER_MODE_SELECT));

    

    //I2C_AcknowledgeConfig(DS2482_I2C, ENABLE);

    

    /* Send DS2482 address for write */

    I2C_Send7bitAddress(DS2482_I2C, DS2482_I2C_ADDRESS, I2C_Direction_Transmitter);

#i2c-example-stm32

[neoirto]

Posted on November 01, 2012 at 11:41

I had the same problem yesterday : found a fix like this :

I2C_Send7bitAddress(DS2482_I2C, DS2482_I2C_ADDRESS, I2C_Direction_Transmitter);

becomes :

I2C_Send7bitAddress(DS2482_I2C, (DS2482_I2C_ADDRESS<<1), I2C_Direction_Transmitter);

It appears you need to shift manually... It's quite a bit strange with a complete library from ST. Is there any i2c config flag to set a different way ?

[ngoclt]

Posted on November 01, 2012 at 20:41

Thanks for pointing it out! I double checked and yes, the slave address needs to be shifted. It is working now :).

[Amel NASRI]

Posted on February 25, 2013 at 12:02

Hi Stephane,

This shouldn't be a bug as the address is a user defined parameter.

The correct format is specified in reference manuals (The 7 bit device address...is placed in the most significant bits of the byte. The eighth bit can be a zero or one.).

Best Regards,

ST.MCU