I2C slave: прием и передача

RCC->AHB1ENR |= RCC_AHB1ENR_GPIOBEN;
RCC->APB1ENR |= RCC_APB1ENR_I2C1EN;
 
// Настройка GPIO, PB6,PB7 на I2C1
GPIOB->MODER |= GPIO_MODER_MODER6_1 | GPIO_MODER_MODER7_1;   // AF
GPIOB->OTYPER |= GPIO_OTYPER_OT_6 | GPIO_OTYPER_OT_7;      // Open-Drain
GPIOB->PUPDR |= GPIO_PUPDR_PUPDR6_0 | GPIO_PUPDR_PUPDR7_0;   // Pull-Up
GPIOB->AFR[0] |= GPIO_AFRL_6_2 | GPIO_AFRL_7_2;            // AF4 -> I2C
 
// Настройка I2C1
I2C1->CR1 |= I2C_CR1_ACK;
I2C1->CR2 |= I2C_CR2_FREQ_1;
I2C1->OAR1 |= I2C_OAR1_ADD3 | I2C_OAR1_RESERVED_14;
I2C1->CCR &= ~I2C_CCR_CCR;
I2C1->CCR |= 0x0A;
I2C1->TRISE = 3;
I2C1->CR1 |= I2C_CR1_PE;
 
I2C1->CR1 |= I2C_CR1_START;  // Send START
while (!(I2C1->SR1 & I2C_SR1_SB));
 
(void) I2C1->SR1;
I2C1->DR = 0xA0;  // Send address
while (!(I2C1->SR1 & I2C_SR1_ADDR));
 
(void) I2C1->SR1;
(void) I2C1->SR2;
 
I2C1->DR = 0xCD;  // Transmit data
while (!(I2C1->SR1 & I2C_SR1_BTF));

#define BIT(x)   (1<<x)
 
#define GPIO_AFRL_6_0   BIT(24)
#define GPIO_AFRL_6_1   BIT(25)
#define GPIO_AFRL_6_2   BIT(26)
#define GPIO_AFRL_6_3   BIT(27)
 
#define GPIO_AFRL_7_0   BIT(28)
#define GPIO_AFRL_7_1   BIT(29)
#define GPIO_AFRL_7_2   BIT(30)
#define GPIO_AFRL_7_3   BIT(31)

I2C1->CR2 |= I2C_CR2_FREQ_1;
I2C1->OAR1 |= 0xD0;         // 7bit address: 0x68 (*2)
I2C1->CCR &= ~I2C_CCR_CCR;
I2C1->CCR |= 10;
I2C1->TRISE = 3;
I2C1->CR1 |= I2C_CR1_PE;      // Enable I2C btock
I2C1->CR1 |= I2C_CR1_ACK;