stm32 study notes--serial port baud rate

What are the problems with the study these days? When I started to look at the first few routines, I seemed to find some feelings and learned some things, such as how to calculate the baud rate that the serial port needs to configure, how to implement the addressing operation of a single bit of the I/O port through the design of the bit band alias area, how to set the port mode, and the respective advantages and disadvantages of spi and iic. I read so much last week, and now I think that these are the only ones left. Then this week, the feeling of this week is even less solid. Many things are just a cursory glance and forgotten after reading, such as interrupt control. It was not until the second time that the framework was formed, the various experiments of watchdog DMA game controller infrared communication, well, I only know what these things are, and my understanding of them is not even as good as the modules of last week. At least there is a framework. At this point, there is only "Oh, this, I know..." and that's it, right! That's it. So the next step is to modify the program, no matter what program you modify, of course it is best to modify the program of the three-axis accelerometer directly, modify it casually, and you can see the effect on the board after the modification. Do this kind of thing. If there is nothing to modify in this module, modify something else. Anyway, you have to start modifying it. You can't just look at it like this. Okay, let's try it tomorrow.