SPI

STM32 SPI library has been modified with the possibility to manage hardware CS pin linked to the SPI peripheral. This section documents STM32-specific additions to the standard SPI API.

There are two ways to manage the CS pin:

the CS pin is managed directly by the user code before to transfer the data (like the Arduino SPI library)
the user uses a hardware CS pin linked to the SPI peripheral

New SPISetting parameter

noReceive: value can be SPI_TRANSMITRECEIVE or SPI_TRANSMITONLY. It allows to skip receive data after transmitting.

New API functions

SPIClass::SPIClass(uint8_t mosi, uint8_t miso, uint8_t sclk, uint8_t ssel): alternative class constructor Params SPI mosi pin Params SPI miso pin Params SPI sclk pin Params (optional) SPI ssel pin. This pin must be an hardware CS pin. If you configure this pin, the chip select will be managed by the SPI peripheral.

Example

This is an example of the use of the hardware CS pin linked to the SPI peripheral:

#include <SPI.h>
//            MOSI  MISO  SCLK   SSEL
SPIClass SPI_3(PC12, PC11, PC10, PC9);
SPISettings settings(1000000, MSBFIRST, SPI_MODE0);

void setup() {
  SPI_3.begin(); // Enable the SPI_3 instance with default SPISsettings
  SPI_3.beginTransaction(settings); // Configure the SPI_3 instance
  SPI_3.transfer(0x52); // Transfers data to the first device
  SPI_3.end(); // SPI_3 instance is disabled
}

Change default `SPI` instance pins

It is also possible to change the default pins used by the SPI instance using above API:

Warning

Have to be called before begin().

void setMISO(uint32_t miso)
void setMOSI(uint32_t mosi)
void setSCLK(uint32_t sclk)
void setSSEL(uint32_t ssel)
void setMISO(PinName miso)
void setMOSI(PinName mosi)
void setSCLK(PinName sclk)
void setSSEL(PinName ssel)

Note

Using setSSEL() allows to enable hardware CS pin management linked to the SPI peripheral.

Example:

    SPI.setMISO(PC_4); // using pin name PY_n
    SPI.setMOSI(PC2); // using pin number PYn
    SPI.begin(2);

SPI