STM32F4_I2C_CR1_START
stm32f4_i2c_set_bits(reg, STM32F4_I2C_CR1_START);
stm32f4_i2c_set_bits(reg, STM32F4_I2C_CR1_START);
cr1 |= STM32F4_I2C_CR1_START;
stm32f4_i2c_set_bits(reg, STM32F4_I2C_CR1_START);