Recently I was studying the SPI protocol. I learned that SPI has 4 modes according to the difference between CPOL and CPHA, but I haven't figured out why these four modes should be developed. Everyone is unified into one of them, isn't it more versatile? Please master answer.
Nolan Posted on September 21, 2020
Because at that time there were many companies with their own standards.
Melanie Posted on September 21, 2020
For different hardware boards, the pull-up and pull-down of the SPI interface may be inconsistent. In this case, the SPI mode configuration is required. However, most of the current usage patterns are just one of them. The reason is that a hundred schools of thought were contending at that time, and their design standards were different.
Brody Posted on September 21, 2020
Patent issues, such as STM32's I2C, many people have reported that there are problems, and it is designed to avoid problems with patent results.
