STM32 SPI mode

1. SPI protocol (Serial Peripheral Interface), also known as serial peripheral interface, is a high-speed full-duplex

Communication bus, it was proposed by Motorola, and the latest version is V04.01-2004.

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2. There are four SPI modes according to the different configurations of SPI clock polarity (CPOL) and clock phase (CPHA). 

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4. The clock polarity refers to when the SPI communication device is in idle state (it can also be considered that this is when the SPI communication starts, that is, the SS line

When CPOL=0, SCK is at a low level in idle state, and vice versa when CPOL=1. 

The clock phase refers to the moment of data sampling. When CPHA=0, the signal on the MOSI or MISO data line will be sampled on the odd edge of the SCK clock line. When CPHA=1, the data line is sampled on the even edge of SCK. 

Mode0: CPOL= 0, CPHA=0; 

Mode1: CPOL= 0, CPHA=1; 
Mode2: CPOL= 1, CPHA=0; 
Mode3: CPOL=1, CPHA= 1;

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2. SPI features of STM32: 
   

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4. The small capacity STM32 products have one SPI interface, the medium capacity ones have two, and the large capacity ones have three.

as follows: 

①Single transmission can be selected as 8 or 16 bits; 

② Baud rate pre-scaling factor (maximum is fpclk/2); 

③Clock polarity (CPOL) and phase (CPHA) can be programmed; 

④The transmission order of data sequence can be programmed, MSB first or LSB first; 

⑤ Dedicated send and receive flags that can trigger interrupts; 

⑥DMA can be used for data transfer operations.