fastspi_bitbang.h

#ifndef __INC_FASTSPI_BITBANG_H
#define __INC_FASTSPI_BITBANG_H

#include "FastLED.h"

#include "fastled_delay.h"

FASTLED_NAMESPACE_BEGIN

//
// Software SPI (aka bit-banging) support - with aggressive optimizations for when the clock and data pin are on the same port
//
// TODO: Replace the select pin definition with a set of pins, to allow using mux hardware for routing in the future
//

template <uint8_t DATA_PIN, uint8_t CLOCK_PIN, uint8_t SPI_SPEED>
class AVRSoftwareSPIOutput {
    // The data types for pointers to the pin port - typedef'd here from the Pin definition because on avr these
    // are pointers to 8 bit values, while on arm they are 32 bit
    typedef typename FastPin<DATA_PIN>::port_ptr_t data_ptr_t;
    typedef typename FastPin<CLOCK_PIN>::port_ptr_t clock_ptr_t;

    // The data type for what's at a pin's port - typedef'd here from the Pin definition because on avr the ports
    // are 8 bits wide while on arm they are 32.
    typedef typename FastPin<DATA_PIN>::port_t data_t;
    typedef typename FastPin<CLOCK_PIN>::port_t clock_t;
    Selectable  *m_pSelect;

public:
    AVRSoftwareSPIOutput() { m_pSelect = NULL; }
    AVRSoftwareSPIOutput(Selectable *pSelect) { m_pSelect = pSelect; }
    void setSelect(Selectable *pSelect) { m_pSelect = pSelect; }

    void init() {
        // set the pins to output and make sure the select is released (which apparently means hi?  This is a bit
        // confusing to me)
        FastPin<DATA_PIN>::setOutput();
        FastPin<CLOCK_PIN>::setOutput();
        release();
    }

    // stop the SPI output.  Pretty much a NOP with software, as there's no registers to kick
    static void stop() { }

    // wait until the SPI subsystem is ready for more data to write.  A NOP when bitbanging
    static void wait() __attribute__((always_inline)) { }
    static void waitFully() __attribute__((always_inline)) { wait(); }

    static void writeByteNoWait(uint8_t b) __attribute__((always_inline)) { writeByte(b); }
    static void writeBytePostWait(uint8_t b) __attribute__((always_inline)) { writeByte(b); wait(); }

    static void writeWord(uint16_t w) __attribute__((always_inline)) { writeByte(w>>8); writeByte(w&0xFF); }

    // naive writeByte implelentation, simply calls writeBit on the 8 bits in the byte.
    static void writeByte(uint8_t b) {
        writeBit<7>(b);
        writeBit<6>(b);
        writeBit<5>(b);
        writeBit<4>(b);
        writeBit<3>(b);
        writeBit<2>(b);
        writeBit<1>(b);
        writeBit<0>(b);
    }

private:
    // writeByte implementation with data/clock registers passed in.
    static void writeByte(uint8_t b, clock_ptr_t clockpin, data_ptr_t datapin)  {
        writeBit<7>(b, clockpin, datapin);
        writeBit<6>(b, clockpin, datapin);
        writeBit<5>(b, clockpin, datapin);
        writeBit<4>(b, clockpin, datapin);
        writeBit<3>(b, clockpin, datapin);
        writeBit<2>(b, clockpin, datapin);
        writeBit<1>(b, clockpin, datapin);
        writeBit<0>(b, clockpin, datapin);
    }

    // writeByte implementation with the data register passed in and prebaked values for data hi w/clock hi and
    // low and data lo w/clock hi and lo.  This is to be used when clock and data are on the same GPIO register,
    // can get close to getting a bit out the door in 2 clock cycles!
    static void writeByte(uint8_t b, data_ptr_t datapin,
                          data_t hival, data_t loval,
                          clock_t hiclock, clock_t loclock) {
        writeBit<7>(b, datapin, hival, loval, hiclock, loclock);
        writeBit<6>(b, datapin, hival, loval, hiclock, loclock);
        writeBit<5>(b, datapin, hival, loval, hiclock, loclock);
        writeBit<4>(b, datapin, hival, loval, hiclock, loclock);
        writeBit<3>(b, datapin, hival, loval, hiclock, loclock);
        writeBit<2>(b, datapin, hival, loval, hiclock, loclock);
        writeBit<1>(b, datapin, hival, loval, hiclock, loclock);
        writeBit<0>(b, datapin, hival, loval, hiclock, loclock);
    }

    // writeByte implementation with not just registers passed in, but pre-baked values for said registers for
    // data hi/lo and clock hi/lo values.  Note: weird things will happen if this method is called in cases where
    // the data and clock pins are on the same port!  Don't do that!
    static void writeByte(uint8_t b, clock_ptr_t clockpin, data_ptr_t datapin,
                          data_t hival, data_t loval,
                          clock_t hiclock, clock_t loclock) {
        writeBit<7>(b, clockpin, datapin, hival, loval, hiclock, loclock);
        writeBit<6>(b, clockpin, datapin, hival, loval, hiclock, loclock);
        writeBit<5>(b, clockpin, datapin, hival, loval, hiclock, loclock);
        writeBit<4>(b, clockpin, datapin, hival, loval, hiclock, loclock);
        writeBit<3>(b, clockpin, datapin, hival, loval, hiclock, loclock);
        writeBit<2>(b, clockpin, datapin, hival, loval, hiclock, loclock);
        writeBit<1>(b, clockpin, datapin, hival, loval, hiclock, loclock);
        writeBit<0>(b, clockpin, datapin, hival, loval, hiclock, loclock);
    }

public:

    // We want to make sure that the clock pulse is held high for a nininum of 35ns.
    #define MIN_DELAY (NS(35) - 3)

  #define CLOCK_HI_DELAY delaycycles<MIN_DELAY>(); delaycycles<(((SPI_SPEED-6) / 2) - MIN_DELAY)>();
    #define CLOCK_LO_DELAY delaycycles<(((SPI_SPEED-6) / 4))>();

    // write the BIT'th bit out via spi, setting the data pin then strobing the clcok
    template <uint8_t BIT> __attribute__((always_inline, hot)) inline static void writeBit(uint8_t b) {
        //cli();
        if(b & (1 << BIT)) {
            FastPin<DATA_PIN>::hi();
            FastPin<CLOCK_PIN>::hi(); CLOCK_HI_DELAY;
            FastPin<CLOCK_PIN>::lo(); CLOCK_LO_DELAY;
        } else {
            FastPin<DATA_PIN>::lo();
            FastPin<CLOCK_PIN>::hi(); CLOCK_HI_DELAY;
            FastPin<CLOCK_PIN>::lo(); CLOCK_LO_DELAY;
        }
        //sei();
    }

private:
    // write the BIT'th bit out via spi, setting the data pin then strobing the clock, using the passed in pin registers to accelerate access if needed
    template <uint8_t BIT> __attribute__((always_inline)) inline static void writeBit(uint8_t b, clock_ptr_t clockpin, data_ptr_t datapin) {
        if(b & (1 << BIT)) {
            FastPin<DATA_PIN>::hi(datapin);
            FastPin<CLOCK_PIN>::hi(clockpin); CLOCK_HI_DELAY;
            FastPin<CLOCK_PIN>::lo(clockpin); CLOCK_LO_DELAY;
        } else {
            FastPin<DATA_PIN>::lo(datapin);
            FastPin<CLOCK_PIN>::hi(clockpin); CLOCK_HI_DELAY;
            FastPin<CLOCK_PIN>::lo(clockpin); CLOCK_LO_DELAY;
        }

    }

    // the version of write to use when clock and data are on separate pins with precomputed values for setting
    // the clock and data pins
    template <uint8_t BIT> __attribute__((always_inline)) inline static void writeBit(uint8_t b, clock_ptr_t clockpin, data_ptr_t datapin,
                                                    data_t hival, data_t loval, clock_t hiclock, clock_t loclock) {
        // // only need to explicitly set clock hi if clock and data are on different ports
        if(b & (1 << BIT)) {
            FastPin<DATA_PIN>::fastset(datapin, hival);
            FastPin<CLOCK_PIN>::fastset(clockpin, hiclock); CLOCK_HI_DELAY;
            FastPin<CLOCK_PIN>::fastset(clockpin, loclock); CLOCK_LO_DELAY;
        } else {
            // NOP;
            FastPin<DATA_PIN>::fastset(datapin, loval);
            FastPin<CLOCK_PIN>::fastset(clockpin, hiclock); CLOCK_HI_DELAY;
            FastPin<CLOCK_PIN>::fastset(clockpin, loclock); CLOCK_LO_DELAY;
        }
    }

    // the version of write to use when clock and data are on the same port with precomputed values for the various
    // combinations
    template <uint8_t BIT> __attribute__((always_inline)) inline static void writeBit(uint8_t b, data_ptr_t clockdatapin,
                                                    data_t datahiclockhi, data_t dataloclockhi,
                                                    data_t datahiclocklo, data_t dataloclocklo) {
#if 0
        writeBit<BIT>(b);
#else
        if(b & (1 << BIT)) {
            FastPin<DATA_PIN>::fastset(clockdatapin, datahiclocklo);
            FastPin<DATA_PIN>::fastset(clockdatapin, datahiclockhi); CLOCK_HI_DELAY;
            FastPin<DATA_PIN>::fastset(clockdatapin, datahiclocklo); CLOCK_LO_DELAY;
        } else {
            // NOP;
            FastPin<DATA_PIN>::fastset(clockdatapin, dataloclocklo);
            FastPin<DATA_PIN>::fastset(clockdatapin, dataloclockhi); CLOCK_HI_DELAY;
            FastPin<DATA_PIN>::fastset(clockdatapin, dataloclocklo); CLOCK_LO_DELAY;
        }
#endif
    }
public:

    // select the SPI output (TODO: research whether this really means hi or lo.  Alt TODO: move select responsibility out of the SPI classes
    // entirely, make it up to the caller to remember to lock/select the line?)
    void select() { if(m_pSelect != NULL) { m_pSelect->select(); } } // FastPin<SELECT_PIN>::hi(); }

    // release the SPI line
    void release() { if(m_pSelect != NULL) { m_pSelect->release(); } } // FastPin<SELECT_PIN>::lo(); }

    // Write out len bytes of the given value out over SPI.  Useful for quickly flushing, say, a line of 0's down the line.
    void writeBytesValue(uint8_t value, int len) {
        select();
        writeBytesValueRaw(value, len);
        release();
    }

    static void writeBytesValueRaw(uint8_t value, int len) {
#ifdef FAST_SPI_INTERRUPTS_WRITE_PINS
        // TODO: Weird things may happen if software bitbanging SPI output and other pins on the output reigsters are being twiddled.  Need
        // to allow specifying whether or not exclusive i/o access is allowed during this process, and if i/o access is not allowed fall
        // back to the degenerative code below
        while(len--) {
            writeByte(value);
        }
#else
        register data_ptr_t datapin = FastPin<DATA_PIN>::port();

        if(FastPin<DATA_PIN>::port() != FastPin<CLOCK_PIN>::port()) {
            // If data and clock are on different ports, then writing a bit will consist of writing the value foor
            // the bit (hi or low) to the data pin port, and then two writes to the clock port to strobe the clock line
            register clock_ptr_t clockpin = FastPin<CLOCK_PIN>::port();
            register data_t datahi = FastPin<DATA_PIN>::hival();
            register data_t datalo = FastPin<DATA_PIN>::loval();
            register clock_t clockhi = FastPin<CLOCK_PIN>::hival();
            register clock_t clocklo = FastPin<CLOCK_PIN>::loval();
            while(len--) {
                writeByte(value, clockpin, datapin, datahi, datalo, clockhi, clocklo);
            }

        } else {
            // If data and clock are on the same port then we can combine setting the data and clock pins
            register data_t datahi_clockhi = FastPin<DATA_PIN>::hival() | FastPin<CLOCK_PIN>::mask();
            register data_t datalo_clockhi = FastPin<DATA_PIN>::loval() | FastPin<CLOCK_PIN>::mask();
            register data_t datahi_clocklo = FastPin<DATA_PIN>::hival() & ~FastPin<CLOCK_PIN>::mask();
            register data_t datalo_clocklo = FastPin<DATA_PIN>::loval() & ~FastPin<CLOCK_PIN>::mask();

            while(len--) {
                writeByte(value, datapin, datahi_clockhi, datalo_clockhi, datahi_clocklo, datalo_clocklo);
            }
        }
#endif
    }

    // write a block of len uint8_ts out.  Need to type this better so that explicit casts into the call aren't required.
    // note that this template version takes a class parameter for a per-byte modifier to the data.
    template <class D> void writeBytes(register uint8_t *data, int len) {
        select();
#ifdef FAST_SPI_INTERRUPTS_WRITE_PINS
        uint8_t *end = data + len;
        while(data != end) {
            writeByte(D::adjust(*data++));
        }
#else
        register clock_ptr_t clockpin = FastPin<CLOCK_PIN>::port();
        register data_ptr_t datapin = FastPin<DATA_PIN>::port();

        if(FastPin<DATA_PIN>::port() != FastPin<CLOCK_PIN>::port()) {
            // If data and clock are on different ports, then writing a bit will consist of writing the value foor
            // the bit (hi or low) to the data pin port, and then two writes to the clock port to strobe the clock line
            register data_t datahi = FastPin<DATA_PIN>::hival();
            register data_t datalo = FastPin<DATA_PIN>::loval();
            register clock_t clockhi = FastPin<CLOCK_PIN>::hival();
            register clock_t clocklo = FastPin<CLOCK_PIN>::loval();
            uint8_t *end = data + len;

            while(data != end) {
                writeByte(D::adjust(*data++), clockpin, datapin, datahi, datalo, clockhi, clocklo);
            }

        } else {
            // FastPin<CLOCK_PIN>::hi();
            // If data and clock are on the same port then we can combine setting the data and clock pins
            register data_t datahi_clockhi = FastPin<DATA_PIN>::hival() | FastPin<CLOCK_PIN>::mask();
            register data_t datalo_clockhi = FastPin<DATA_PIN>::loval() | FastPin<CLOCK_PIN>::mask();
            register data_t datahi_clocklo = FastPin<DATA_PIN>::hival() & ~FastPin<CLOCK_PIN>::mask();
            register data_t datalo_clocklo = FastPin<DATA_PIN>::loval() & ~FastPin<CLOCK_PIN>::mask();

            uint8_t *end = data + len;

            while(data != end) {
                writeByte(D::adjust(*data++), datapin, datahi_clockhi, datalo_clockhi, datahi_clocklo, datalo_clocklo);
            }
            // FastPin<CLOCK_PIN>::lo();
        }
#endif
        D::postBlock(len);
        release();
    }

    // default version of writing a block of data out to the SPI port, with no data modifications being made
    void writeBytes(register uint8_t *data, int len) { writeBytes<DATA_NOP>(data, len); }


    // write a block of uint8_ts out in groups of three.  len is the total number of uint8_ts to write out.  The template
    // parameters indicate how many uint8_ts to skip at the beginning of each grouping, as well as a class specifying a per
    // byte of data modification to be made.  (See DATA_NOP above)
    template <uint8_t FLAGS, class D, EOrder RGB_ORDER>  __attribute__((noinline)) void writePixels(PixelController<RGB_ORDER> pixels) {
        select();
        int len = pixels.mLen;

#ifdef FAST_SPI_INTERRUPTS_WRITE_PINS
        // If interrupts or other things may be generating output while we're working on things, then we need
        // to use this block
        while(pixels.has(1)) {
            if(FLAGS & FLAG_START_BIT) {
                writeBit<0>(1);
            }
            writeByte(D::adjust(pixels.loadAndScale0()));
            writeByte(D::adjust(pixels.loadAndScale1()));
            writeByte(D::adjust(pixels.loadAndScale2()));
            pixels.advanceData();
            pixels.stepDithering();
        }
#else
        // If we can guaruntee that no one else will be writing data while we are running (namely, changing the values of the PORT/PDOR pins)
        // then we can use a bunch of optimizations in here
        register data_ptr_t datapin = FastPin<DATA_PIN>::port();

        if(FastPin<DATA_PIN>::port() != FastPin<CLOCK_PIN>::port()) {
            register clock_ptr_t clockpin = FastPin<CLOCK_PIN>::port();
            // If data and clock are on different ports, then writing a bit will consist of writing the value foor
            // the bit (hi or low) to the data pin port, and then two writes to the clock port to strobe the clock line
            register data_t datahi = FastPin<DATA_PIN>::hival();
            register data_t datalo = FastPin<DATA_PIN>::loval();
            register clock_t clockhi = FastPin<CLOCK_PIN>::hival();
            register clock_t clocklo = FastPin<CLOCK_PIN>::loval();

            while(pixels.has(1)) {
                if(FLAGS & FLAG_START_BIT) {
                    writeBit<0>(1, clockpin, datapin, datahi, datalo, clockhi, clocklo);
                }
                writeByte(D::adjust(pixels.loadAndScale0()), clockpin, datapin, datahi, datalo, clockhi, clocklo);
                writeByte(D::adjust(pixels.loadAndScale1()), clockpin, datapin, datahi, datalo, clockhi, clocklo);
                writeByte(D::adjust(pixels.loadAndScale2()), clockpin, datapin, datahi, datalo, clockhi, clocklo);
                pixels.advanceData();
                pixels.stepDithering();
            }

        } else {
            // If data and clock are on the same port then we can combine setting the data and clock pins
            register data_t datahi_clockhi = FastPin<DATA_PIN>::hival() | FastPin<CLOCK_PIN>::mask();
            register data_t datalo_clockhi = FastPin<DATA_PIN>::loval() | FastPin<CLOCK_PIN>::mask();
            register data_t datahi_clocklo = FastPin<DATA_PIN>::hival() & ~FastPin<CLOCK_PIN>::mask();
            register data_t datalo_clocklo = FastPin<DATA_PIN>::loval() & ~FastPin<CLOCK_PIN>::mask();

            while(pixels.has(1)) {
                if(FLAGS & FLAG_START_BIT) {
                    writeBit<0>(1, datapin, datahi_clockhi, datalo_clockhi, datahi_clocklo, datalo_clocklo);
                }
                writeByte(D::adjust(pixels.loadAndScale0()), datapin, datahi_clockhi, datalo_clockhi, datahi_clocklo, datalo_clocklo);
                writeByte(D::adjust(pixels.loadAndScale1()), datapin, datahi_clockhi, datalo_clockhi, datahi_clocklo, datalo_clocklo);
                writeByte(D::adjust(pixels.loadAndScale2()), datapin, datahi_clockhi, datalo_clockhi, datahi_clocklo, datalo_clocklo);
                pixels.advanceData();
                pixels.stepDithering();
            }
        }
#endif
        D::postBlock(len);
        release();
    }
};

FASTLED_NAMESPACE_END

#endif