SYSCLK clock source three sources: HSI RC, HSE OSC, PLL

1. SYSCLK clock source has three sources: HSI RC, HSE OSC, PLL

2. MCO[2:0] can provide 4 sources of different clock synchronization signals, PA8

3. The GPIO port seems to have two reverse-connected series diodes used as clamping diodes.

4. ICode bus, DCode bus, system bus, DMA bus, bus matrix, AHB/APB bridge

5. Before using a peripheral, you must set the register RCC_AHBENR to turn on the clock of the peripheral.

6. There are three types of STM32 reset: system reset, power-on reset, and backup area reset. In system reset, except for the reset flag in RCC_CSR and the value in BKP, all other registers are reset.

Trigger modes include external reset, watchdog reset, software reset, etc.; power reset is due to external power-on/power-off reset or return from standby mode.

During a reset, all register values ​​in BKP remain unchanged, while all others are reset. The trigger source for resetting the backup area is a software reset or when both VDD and VBAT are powered off.

7. (Nested Vectored Interrupt Controller) NVIC nested vector interrupt controller, divided into two types: preemptive priority (nestable) and interrupt priority (secondary priority, cannot be nested).

The two priorities are determined by 4 binary bits. There are 16 cases:

8. Automatically load registers and shadow registers: The former is equivalent to the overflow setting value in 51. The shadow register, as the name implies, is a shadow, which is another copy of the register.

The shadow register actually works, and the programmer manipulates the auto-load register. If the APPE bit is enabled, it indicates that the value of the auto-load register will be written to the new value after the next update event occurs.

Otherwise, the value written to the auto-load register is immediately updated to the shadow register.

9,

11. Principle of capacitive touch screen: detect whether it is pressed by the difference in charge and discharge curves. In the actual experiment, TPAD can be replaced by a copper-clad area, and the charge and discharge constant of the capacitor is used to determine whether it is pressed.

12. OLED, or organic light-emitting diode, is also known as organic laser display. The following figure shows the correspondence between OLED's GRAM and screen

PAGE2 is listed separately:

13. USART can operate SPI devices. However, the maximum frequency is only 4.5MHz

14. Issues that should be noted when using I/O ports

15. The ADC 's Vref +, Vdda, VSS, and Vref- must be connected with high-quality filter capacitors and cut close to the microcontroller .