How to properly initialize I2C stm32?

StackOverflow https://stackoverflow.com/questions/8312998

Question

I want to get data from ADXL345 accelerometer,but seems that I incorrectly connect it.

SCL- PC6(with 10k resistor)

SDA- PC7(with 10k resistor)

SDO- GND

CS - VCC

GND - GND

3.3v - VCC

Here is my code to initalize:

void I2CG_Init(void)
{
    GPIO_InitTypeDef  GPIO_InitStructure;
    I2C_InitTypeDef  I2C_InitStructure;

    RCC_AHBPeriphClockCmd(RCC_APB2Periph_AFIO, ENABLE);
    RCC_AHBPeriphClockCmd(RCC_APB2Periph_GPIOC, ENABLE);
        // I2CG clock enable
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_I2CG, ENABLE);
    RCC_AHBPeriphClockCmd(RCC_APB1Periph_I2CG, ENABLE);
    // GPIOB clock enable
    // I2CG SCL and SDA configuration
    GPIO_InitStructure.GPIO_Pin = SCL|SDA;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_OD;
    GPIO_InitStructure.GPIO_Speed=GPIO_Speed_50MHz;
    GPIO_Init(GPIOC, &GPIO_InitStructure);
    // Enable I2CG reset state
    RCC_APB1PeriphResetCmd(RCC_APB1Periph_I2CG, ENABLE);
       // Release I2CG from reset state
       RCC_APB1PeriphResetCmd(RCC_APB1Periph_I2CG, DISABLE);
    I2C_DeInit(I2C1);
    I2C_InitStructure.I2C_Mode = I2C_Mode_I2C;
    I2C_InitStructure.I2C_DutyCycle = I2C_DutyCycle_16_9;
    I2C_InitStructure.I2C_OwnAddress1 =  1;
    I2C_InitStructure.I2C_Ack = I2C_Ack_Enable;
    I2C_InitStructure.I2C_AcknowledgedAddress = I2C_AcknowledgedAddress_7bit;
    I2C_InitStructure.I2C_ClockSpeed = ClockSpeed;


    I2C_Init(I2CG, &I2C_InitStructure);
    I2C_Cmd(I2CG, ENABLE);
    I2C_AcknowledgeConfig(I2CG, ENABLE);
}

In one example I saw 

GPIO_PinAFConfig(GPIOC,SCLSource,GPIO_AF_I2CG);

GPIO_PinAFConfig(GPIOC,SDASource,GPIO_AF_I2CG);

But I don't have this API available.

Please help me. I tried many solutions and also tried to connect through SPI, but no success :( Please help with I2C.

Was it helpful?

Solution

SCL- PC6(with 10k resistor)

SDA- PC7(with 10k resistor)

SCL and SDA should be connected directly. You should use pull-up resistors like on this scheme: http://en.wikipedia.org/wiki/File:I2C.svg

Your initialization code looks ok, so maybe hardware wiring is wrong?

OTHER TIPS

I realise this is an old post but it's worth pointing out. You shouldn't be using APB flags to configure the AHB bus. Check the programmers manual RM0008 (assuming you're using a stm32f10x device) for the appropriate settings.

I had the same problem as you. The start condition was generated but the I2Cx_SR1.SB bit doesn't get set. I thought that I had to enable the I2C alternate function, but I had to disable all the other functions in the pin too. In my case it was UART3 function conflicting with I2C.

There's sample code and app notes for the STM32 by someone who claims to have gotten I2C working here:

http://www.stm32challenge.com/node/143

Maybe try to get something known like a serial EEPROM working before you try the unknown accelerometer. Once you are sure the microcontroller end works you can connect the accelerometer and see what you get.

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