Why is there 4 modes in SPI?
SPI has four modes (0,1,2,3) that correspond to the four possible clocking configurations. Bits that are sampled on the rising edge of the clock cycle are shifted out on the falling edge of the clock cycle, and vice versa. Note that data must be available before the first rising edge of the clock.
What is SPI stm32?
SPI is a bus, which means you can use multiple peripheral devices for one controller. All of the lines are shared except for the CS line. You will need to dedicate one pin on your controller as a separate CS line for each peripheral you wish to communicate with.
What is SPI master mode?
In master mode, the SPI generates the synchronous communication clock at one of four master frequencies. The maximum master mode frequency is half the bus frequency. For most 68HC08 MCUs, the maximum bus frequency is 8 MHz, allowing up to 4 MHz master mode clock rates.
What is NSS signal SPI?
The active-low slave-select (NSS) signal allows support for multiple slave devices on a single bus. It is also used to detect the start and end of a SPI transfer for CP2400/2, and should be connected to the SPI master instead of connection to a static low level signal, e.g. GND.
How to use the SPI interface on STM32 devices?
We will configure the SPI in several different modes, show how they affect the generated signal and setup the double-buffered mode to demonstrate continuous uninterrupted mode. We will use an STM32F4Discovery board to demonstrate the SPI and a Nucleo-F411RE board with Analyzer2Go to capture and analyze the generated SPI signals.
When to use mode 0 in SPI slave communication?
If CPOL and CPHA are both ‘0’ (defined as Mode 0) data is sampled at the leading rising edge of the clock. Mode 0 is by far the most common mode for SPI bus slave communication. If CPOL is ‘1’ and CPHA is ‘0’ (Mode 2), data is sampled at the leading falling edge of the clock.
What is the protocol for the SPI interface?
The SPI interface defines no protocol for data exchange, limiting overhead and allowing for high speed data streaming. Clock polarity (CPOL) and clock phase (CPHA) can be specified as ‘0’ or ‘1’ to form four unique modes to provide flexibility in communication between master and slave as shown in Figure 2.
What are the alternate pin functions of stm32f100xx?
Note also that the function of PD0 (pin5) and PD1 (pin6) can be remapped by software. The image below shows the alternate pin functions of STM32F100xx devices. The alternate functions are the internal peripheral device connections to the external pins. Alternate functions shown in red can be remapped to other port pins.