STM32F401RE: I2C code works only while single stepping in debug mode

[ORaji.1]

Good day, I'm trying to interface the STM32F401RE with a DS3231 RTC module. The idea is to read from the time-keeping registers of the RTC module. Based on the code, I decided to set the 'hour' register to 6 and when the register is read, 6 is expected to be read. This code only works while single stepping in debug mode and not at runtime. I don't know why this is happening but if there's something I'm missing or getting wrong, I'd be glad to know.

The source code is in the attached file below.

[KnarfB]

Don't want to dig deep into your register level code, just one remark:

if ((I2C1->SR1 & I2C_SR1_TXE)){

This should be a while loop where the code waits spinning in that loop until transmission is completed.