STM32F4_I2C_CR1_ACK
stm32f4_i2c_clr_bits(reg, STM32F4_I2C_CR1_ACK);
cr1 &= ~(STM32F4_I2C_CR1_ACK | STM32F4_I2C_CR1_POS);
cr1 &= ~STM32F4_I2C_CR1_ACK;
cr1 |= STM32F4_I2C_CR1_ACK;