1. Main difference between hardware SPI and software SPI

1) Sequence：No difference

2) SPI speed： Hardware SPI is more efficient. When writing a program, you only need to write the data to be sent to the register, and the hardware will send it automatically. The software SPI requires additional steps such as SCLK to output high and low level, data serial output and so on.

3) Hardware requirement：Hardware SPI must be supported by the processor before it can be used. Software SPI does not need specific requirements. A general IO port is OK.

2. Comparison of corresponding signal lines：