Микроконтроллеры

static void
slow_fast(bool slow)
{
    I2C1->CCR = (slow ? I2C_CCR_FS | 16 : I2C_CCR_FS | 8);
}

void
i2c_init(void)
{
    // the resulting SCL rate when switched to 'fast' is 1.45 MHz (1/29 APB1 clock rate)
    I2C1->CR2   = I2C_CR2_ITEVTEN
                | I2C_CR2_ITERREN
                | (SYSTIME_TPS / 2000000 / 2); // APB1 clock in MHz divided by 4 (accelerate!)
    slow_fast(true);
    I2C1->TRISE = 4;
    I2C1->CR1 = I2C_CR1_ACK | I2C_CR1_PE;
    NVIC_SetPriority(I2C1_EV_IRQn, 1);
    NVIC_SetPriority(I2C1_ER_IRQn, 1);
}