STM32F10x I2C Bus - No Clock and Data on Bus

[ngoclt]

Posted on September 21, 2012 at 20:25

Hi All,

I am seeking help on why I2C2 bus is not communicating. I can see a start condition and then CLK is held low while DATA is held high. Any guidance would be appreciated. Thanks. &sharpinclude ''oneWire.h''&sharpinclude ''stm32f10x_lib.h''&sharpinclude ''stm32f10x_i2c.h''&sharpinclude ''stm32f10x_rcc.h''void DS2482_Init(void){        GPIO_InitTypeDef    GPIO_InitStructure;        I2C_InitTypeDef     I2C_InitStructure;                I2C_DeInit(DS2482_I2C);                /* Enable peripheral clock */        RCC_APB1PeriphClockCmd(RCC_APB1Periph_I2C2, ENABLE);        /* Enable GPIOB clock */        RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB, ENABLE);        /* Enable AFIO clock */        RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO, ENABLE);             /* Configure I2C2_SCL and I2C2_SDA */        GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10 | GPIO_Pin_11;        GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_OD;        GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;        GPIO_Init(GPIOB, &GPIO_InitStructure);        /* DS2483 peripheral configuration */        I2C_InitStructure.I2C_Mode = I2C_Mode_I2C;         I2C_InitStructure.I2C_DutyCycle = I2C_DUTYCYCLE;        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));        I2C_GenerateSTART(DS2482_I2C, ENABLE);        while(!I2C_CheckEvent(DS2482_I2C, I2C_EVENT_MASTER_MODE_SELECT));        I2C_AcknowledgeConfig(DS2482_I2C, ENABLE);    //I2C_Send7bitAddress(DS2482_I2C, DS2482_I2C_ADDRESS, I2C_Direction_Transmitter);    I2C_Send7bitAddress(DS2482_I2C, 0x30, I2C_Direction_Transmitter);        while(!I2C_CheckEvent(DS2482_I2C, I2C_EVENT_MASTER_TRANSMITTER_MODE_SELECTED));              I2C_SendData(DS2482_I2C, DS2482_CHSL);    switch (channel) {    default: case 0: ch = 0xF0; ch_read = 0xB8; break;    case 1: ch = 0xE1; ch_read = 0xB1; break;    case 2: ch = 0xD2; ch_read = 0xAA; break;    case 3: ch = 0xC3; ch_read = 0xA3; break;    case 4: ch = 0xD4; ch_read = 0x9C; break;    case 5: ch = 0xE5; ch_read = 0x95; break;    case 6: ch = 0x96; ch_read = 0x8E; break;    case 7: ch = 0x87; ch_read = 0x87; break;    };    I2C_SendData(DS2482_I2C, ch);    // send START condition a second time    I2C_GenerateSTART(DS2482_I2C, ENABLE);    // send DS2482 address for read     I2C_Send7bitAddress(DS2482_I2C, DS2482_I2C_ADDRESS, I2C_Direction_Receiver);    check = I2C_ReceiveData(DS2482_I2C);       // send STOP condition    I2C_GenerateSTOP(DS2482_I2C, ENABLE);      return (check == ch_read);} #stm32f10x

[rob239955_stm1]

Posted on November 29, 2012 at 20:45

Hopefully you've resolved this by now, but this might help the next person to come along.  I ran into a similar problem on my STM32F100C8, and I narrowed it down to the AFIO being enabled.  What I had to do was enable the AFIO, do my remapping, then disable the AFIO periphery. Then I set up the I2C and it works fine, and it appears the remapping persists.  I don't have a lot of experience on this yet, but it looks to be a viable solution.

Question is, why does enabling the AFIO periphery mess with I2C?  I tried to disable the remap of the I2C, thinking it somehow remapped it automatically, but that didn't seem to be the case.  Nothing in the documentation jumped out at me.

[Tesla DeLorean]

Posted on November 29, 2012 at 21:10

You have to enable the AFIO clock to do the remapping because that's where the mapping register/latches are situated, are you saying the AFIO clock must then be disabled before the I2C will work?

The OP isn't remapping the pins.

[rob239955_stm1]

Posted on November 29, 2012 at 21:51

That is correct.  The actual remapping call did not affect I2C, but enabling the AFIO peripheral did.  (I wasn't remapping anything for the I2C, but disabling JTAG as we use 2-wire SWD only and needed to repurpose the JTAG lines.  This came up as a side-effect).

As a side note, the AFIO doesn't show up as a peripheral in the block diagram or clock tree in the RM, so it took me a little while to figure out it needed to be enabled before the remap command would be effective.

[rob239955_stm1]

Posted on December 03, 2012 at 17:45

Update:

That's apparently only during I2C initialization.  After the I2C is up, I added some more code and enable the AFIO again, and this time I leave it enabled and everything is working. Again, this is the STM32F100C8T6B.  I don't see an obvious date code on the chip.