I used the IO of stc89c51 to generate a square wave with a high level of 5v, a low level of 0V, and a duty cycle of 1kHZ and 80%, and then connected the IO to a transistor (as shown in the figure) to ...
The existing BSP only supports one SD card. (Question 1: Generally speaking, the CPU should be able to support multiple SD cards physically, and it should have relevant registers to indicate the numbe...