I2C busy flag is always set. (without library)

[Min Seok Kim]

Posted on September 13, 2017 at 15:26

MCU : STM32F405

I wish to use I2C without library.

But, I got always busy flag on I2C_SR2 register

---------------------------------------------------------------------------

void set_gpio_af_i2c()

{

RCC_AHB1ENR |= GPIOBEN;

GPIOB_MODER |= (AF_MODE << MODER10 | AF_MODE << MODER11);

GPIOB_PUPDR |= (PULLUP << PUPDR10 | PULLUP << PUPDR11);

GPIOB_OSPEEDR |= (3 << 20 | 3 << 22);

GPIOB_OTYPER |= ( 1 << 10 | 1 << 11);

GPIOB_AFRH |= (AF4 << AFRH10 | AF4 << AFRH11);

}

---------------------------------------------------------------------------

I use the I2C2(SDA : PORTB10, SCL  : PORTB11). 

Initialize GPIOB10, 11 as af mode4, pull_up open drain, very high speed.

---------------------------------------------------------------------------

void i2c_setup()

{

RCC_APB1ENR |= (1 << I2C2EN);

I2C_CR1 |= 1 << SWRST;

I2C_CR1 &= ~(1 << SWRST);

I2C_CR2 |= 42;

I2C_CCR |= 210;

I2C_TRISE = 13;

}

---------------------------------------------------------------------------

And I initialize I2C like this, SWRESET, set PCLK, set CCR, set TRISE

---------------------------------------------------------------------------

I2C_CR1 |= 1 << PE;

I2C_CR1 |= 1 << ACK;

I2C_CR1 |= 1 << START;

// /* Wait until SB flag is set

while( !(I2C_SR1 & 1 << SB) );

---------------------------------------------------------------------------

Finally, I start like this, set PE, set ACK, set START

But, SB flag dosen't set.

SR2's busy flag always set.

How I can solve it?

[Amel NASRI]

Posted on September 13, 2017 at 17:45

Hi

buildorder

‌,

Please make sure that I2C clock is enabled after configuring GPIOs.

Another option is to use another pins combination, if available for the package you are using.

Please let me know if this is working.

-Amel

[Min Seok Kim]

Posted on September 14, 2017 at 04:35

Thanks for your reply

I have a hard time in 2 days. OMG.. It just a shift probelm..

I should like this.

RCC_AHB1ENR |= 1 << GPIOBEN;

but i did

RCC_AHB1ENR |= GPIOBEN;

-Min Seok