SPI Master (Serial Peripheral Interface)

The RP2040 has two hardware SPI interfaces, spi0 (SPI) and spi1 (SPI1). These interfaces are supported by the SPI library in master mode.

SPI pinouts can be set before SPI.begin() using the following calls:

bool setRX(pin_size_t pin);
bool setCS(pin_size_t pin);
bool setSCK(pin_size_t pin);
bool setTX(pin_size_t pin);

Note that the CS pin can be hardware or software controlled by the sketch. When software controlled, the setCS() call is ignored.

The Arduino SPI documentation gives a detailed overview of the library, except for the following RP2040-specific changes:

  • SPI.begin(bool hwCS) can take an options hwCS parameter.

By passing in true for hwCS the sketch does not need to worry about asserting and deasserting the CS pin between transactions. The default is false and requires the sketch to handle the CS pin itself, as is the standard way in Arduino.

  • The interrupt calls (attachInterrupt, and detachInterrpt) are not implemented.

SPI Slave (SPISlave)

Slave mode operation is also supported on either SPI interface. Two callbacks are needed in your app, set through SPISlave.onDataRecv and SPISlave.onDataSent, in order to consunme the received data and provide data to transmit.

  • The callbacks operate at IRQ time and may be called very frequently at high SPI frequencies. So, make then small, fast, and with no memory allocations or locking.


See the SPItoMyself example for a complete Master and Slave application.