STM32 how to set a slave I2C port

Question

I have an issue with STM32F0 Discovery. I am using I2C1 (like master) to send start condition and address to I2C2 (slave) on the same board. I am able to generate propertly the signal but the IC2 (slave) is not able to generate an ACK on 9th clk

What's wrong? Here my code about the setup:

 void set_I2C(void){
    GPIO_InitTypeDef GPIO_InitStructure;
    I2C_InitTypeDef I2C_InitStructure;

    RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOB, ENABLE);
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_I2C1, ENABLE);
    /* Configure the I2C clock source. The clock is derived from the HSI */
    RCC_I2CCLKConfig(RCC_I2C1CLK_SYSCLK);


    GPIO_PinAFConfig(GPIOB, GPIO_PinSource6, GPIO_AF_1);
    GPIO_PinAFConfig(GPIOB, GPIO_PinSource7, GPIO_AF_1);


    //Configure pins: SCL and SDA ------------------
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6 | GPIO_Pin_7;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
    GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
    GPIO_InitStructure.GPIO_OType = GPIO_OType_OD;
    GPIO_Init(GPIOB, &GPIO_InitStructure);



    I2C_DeInit(I2C1);
    I2C_Cmd(I2C1, DISABLE);
    I2C_InitStructure.I2C_AnalogFilter = I2C_AnalogFilter_Enable;
    I2C_InitStructure.I2C_DigitalFilter = 0x00;
    I2C_InitStructure.I2C_OwnAddress1 = 0x40;
    I2C_InitStructure.I2C_Mode = I2C_Mode_I2C;
    I2C_InitStructure.I2C_Ack = I2C_Ack_Enable;
    I2C_InitStructure.I2C_Timing =0xB0420F13; //100KHz        

          I2C_InitStructure.I2C_AcknowledgedAddress = I2C_AcknowledgedAddress_7bit;

    I2C_Init(I2C1, &I2C_InitStructure);
    I2C_Cmd(I2C1, ENABLE);


    //Set up of I2C2
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_I2C2, ENABLE);
    RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOB, ENABLE);


    GPIO_PinAFConfig(GPIOB, GPIO_PinSource11, GPIO_AF_1);
    GPIO_PinAFConfig(GPIOB, GPIO_PinSource10, GPIO_AF_1);

    //Configure pins: SCL and SDA ------------------
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_11 | GPIO_Pin_10;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
    GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
    GPIO_InitStructure.GPIO_OType = GPIO_OType_OD;
    GPIO_Init(GPIOB, &GPIO_InitStructure);

    I2C_DeInit(I2C2);
    I2C_Cmd(I2C2, DISABLE);
    I2C_InitStructure.I2C_AnalogFilter = I2C_AnalogFilter_Disable;
    I2C_InitStructure.I2C_DigitalFilter = 0x00;
    I2C_InitStructure.I2C_OwnAddress1 = 0x30; 

    I2C_InitStructure.I2C_Mode = I2C_Mode_I2C;
    I2C_InitStructure.I2C_Ack = I2C_Ack_Enable;

    I2C_InitStructure.I2C_Timing =0xB0420F13;
    I2C_InitStructure.I2C_AcknowledgedAddress = I2C_AcknowledgedAddress_7bit;

    I2C_Init(I2C2, &I2C_InitStructure);
     I2C_Cmd(I2C2, ENABLE);



        I2C_ITConfig(I2C2, I2C_AcknowledgedAddress_7bit, ENABLE);

  NVIC_InitTypeDef NVIC_InitStructure;
 /* Configure the I2C2 interrupt priority */
 NVIC_InitStructure.NVIC_IRQChannel = I2C2_IRQn;
 NVIC_InitStructure.NVIC_IRQChannelPriority=1;
 NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
 NVIC_Init(&NVIC_InitStructure);

}

So, is there anybody able to help me? I am not able to generate the ack on 9th clk. — difedepe

Viacheslav Dobromyslov Viacheslav Dobromyslov · Accepted Answer · 2014-08-12T13:37:44

I had the same problem. It was caused by absence of the required for I2C external pull-up resistors. You can't just use an internal MCU's pull-ups. You MUST use external ones.

Detailed explanation is provided in these articles:

http://www.robot-electronics.co.uk/acatalog/I2C_Tutorial.html

https://electronics.stackexchange.com/questions/1849/is-there-a-correct-resistance-value-for-pull-up-resistors

STM32 how to set a slave I2C port

2 Answers