HardSpiInterface.h

/*
MIT License
 
Copyright (c) 2021 Brian T. Park
 
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
 
The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.
 
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
*/
 
#ifndef ACE_SPI_HARD_SPI_INTERFACE_H
#define ACE_SPI_HARD_SPI_INTERFACE_H
 
#include <stdint.h>
#include <Arduino.h> // digitalWrite()
#include <SPI.h>
 
namespace ace_spi {
 
template <
    typename T_SPI,
    uint32_t T_CLOCK_SPEED = 8000000
>
class HardSpiInterface {
  private:
    // Some of the following constants are defined in <SPI.h> so unfortunately,
    // it is not possible to avoid pulling in the global SPI instance into
    // applications which don't use SPI.
 
  #if defined(ARDUINO_ARCH_STM32) || defined(ARDUINO_ARCH_SAMD)
    static const BitOrder kBitOrder = MSBFIRST;
  #else
    static const uint8_t kBitOrder = MSBFIRST;
  #endif
 
    static const uint8_t kSpiMode = SPI_MODE0;
 
  public:
    explicit HardSpiInterface(T_SPI& spi, uint8_t latchPin) :
        mSpi(spi),
        mLatchPin(latchPin)
    {}
 
    void begin() const {
      // To use Hardware SPI on ESP8266, we must set the SCK and MOSI pins to
      // 'SPECIAL' instead of 'OUTPUT'. This is performed by calling
      // SPI.begin(). Also, unlike other Arduino platforms, the SPIClass on
      // the ESP8266 defaults to controlling the SS/CS pin itself, instead of
      // letting the application code control it. The setHwCs(false) let's
      // HardSpiInterface control the CS/SS pin.
      // https://www.esp8266.com/wiki/doku.php?id=esp8266_gpio_pin_allocations
      #if defined(ESP8266)
        mSpi.setHwCs(false);
      #endif
 
      pinMode(mLatchPin, OUTPUT);
    }
 
    void end() const {
      pinMode(mLatchPin, INPUT);
    }
 
    void beginTransaction() const {
      mSpi.beginTransaction(SPISettings(T_CLOCK_SPEED, kBitOrder, kSpiMode));
      digitalWrite(mLatchPin, LOW);
    }
 
    void endTransaction() const {
      digitalWrite(mLatchPin, HIGH);
      mSpi.endTransaction();
    }
 
    void transfer(uint8_t value) const {
      mSpi.transfer(value);
    }
 
    void transfer16(uint16_t value) const {
      mSpi.transfer16(value);
    }
 
    void send8(uint8_t value) const {
      beginTransaction();
      transfer(value);
      endTransaction();
    }
 
    void send16(uint16_t value) const {
      beginTransaction();
      transfer16(value);
      endTransaction();
    }
 
    void send16(uint8_t msb, uint8_t lsb) const {
      beginTransaction();
      uint16_t value = ((uint16_t) msb) << 8 | (uint16_t) lsb;
      transfer16(value);
      endTransaction();
    }
 
    // Use default copy constructor and assignment operator.
    HardSpiInterface(const HardSpiInterface&) = default;
    HardSpiInterface& operator=(const HardSpiInterface&) = default;
 
  private:
    T_SPI& mSpi;
    uint8_t const mLatchPin;
};
 
} // ace_spi
 
#endif