spi.cpp

//   Copyright 2016-2023 Jean-Francois Poilpret
//
//   Licensed under the Apache License, Version 2.0 (the "License");
//   you may not use this file except in compliance with the License.
//   You may obtain a copy of the License at
//
//       http://www.apache.org/licenses/LICENSE-2.0
//
//   Unless required by applicable law or agreed to in writing, software
//   distributed under the License is distributed on an "AS IS" BASIS,
//   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
//   See the License for the specific language governing permissions and
//   limitations under the License.
 
#include "boards/board_traits.h"
#include "spi.h"
 
#ifdef SPDR
// Handle SPI for ATmega
void spi::init()
{
    synchronized
    {
        using board_traits::SPI_trait;
        // Set MOSI and SCK as Output
        // Set MISO as Input (high impedance)
        // Also set SS as Output (mandatory for Master SPI as per Atmel datasheet)
        SPI_trait::DDR = (SPI_trait::DDR & bits::CBV8(SPI_trait::MISO))
                         | bits::BV8(SPI_trait::MOSI, SPI_trait::SCK, SPI_trait::SS);
        // Set MISO as pullup and force MOSI and SCK low
        SPI_trait::PORT = (SPI_trait::PORT | bits::BV8(SPI_trait::MISO))
                          & ~(bits::BV8(SPI_trait::MOSI, SPI_trait::SCK));
    }
}
#else
// Handle USI for ATtiny
void spi::init()
{
    synchronized
    {
        using board_traits::SPI_trait;
        // Set MOSI and SCK as Output
        // Set MISO as Input (high impedance)
        SPI_trait::DDR = (SPI_trait::DDR & bits::CBV8(SPI_trait::MISO))
                         | bits::BV8(SPI_trait::MOSI, SPI_trait::SCK);
        // Set MISO as pullup and force MOSI and SCK low
        //TODO not sure this is really needed
        // SPI_trait::PORT = (SPI_trait::PORT | bits::BV8(SPI_trait::MISO)) &
        //                   ~(bits::BV8(SPI_trait::MOSI, SPI_trait::SCK));
    }
}
#endif