pw_spi_rp2040

Raspberry Pi RP2040 backend for pw_spi

Unstable C++

pw_spi_rp2040 implements the pw_spi interface using the Raspberry Pi Pico SDK.

The implementation is based on the SPI driver from the Pico SDK. SPI transfers use the blocking driver API which uses busy waiting under the hood.

The PicoSDK’s spi_init() must be called before using the initiator in order to enable the SPI peripheral and set its bus speed.

Note

There is currently no support for RP2040 hardware CSn pins. pw::spi::DigitalOutChipSelector is used instead.

Usage

#include "hardware/spi.h"
#include "pw_digital_io/polarity.h"
#include "pw_digital_io_rp2040/digital_io.h"
#include "pw_spi/chip_selector_digital_out.h"
#include "pw_spi/device.h"
#include "pw_sync/borrow.h"
#include "pw_sync/mutex.h"

constexpr pw::spi::Config kSpiConfig8Bit{
    .polarity = pw::spi::ClockPolarity::kActiveHigh,
    .phase = pw::spi::ClockPhase::kFallingEdge,
    .bits_per_word = pw::spi::BitsPerWord(8),
    .bit_order = pw::spi::BitOrder::kMsbFirst,
};

pw::digital_io::Rp2040DigitalInOut display_cs_pin({
   .pin = 12,
   .polarity = pw::digital_io::Polarity::kActiveLow,
});
DigitalOutChipSelector spi_chip_selector(display_cs_pin);

Rp2040Initiator spi_initiator(spi0);
VirtualMutex spi_initiator_mutex;
Borrowable<Initiator> borrowable_spi_initiator(spi_initiator,
                                               spi_initiator_mutex);
pw::spi::Device spi_8_bit(borrowable_spi_initiator,
                          kSpiConfig8Bit,
                          spi_chip_selector);