SPI master & slave simultaneously

Projects Programming
4

Software SPI on A0 (sck),A1 (miso), A2 (mosi)

// sw_spi.h
#include "Arduino.h"

#ifndef sw_spi_h
#define sw_spi_h

void nokia_spiSetup(void);
uint8_t nokia_spiRec(void);
void nokia_spiSend(uint8_t data);

#endif // sw_spi_h

// sw_spi.cpp
#include "Sd2PinMap.h"
#include "sw_spi.h"

#define SPI_SCK_PIN	A0 //14	// A0 PC0
#define	SPI_MISO_PIN	A1 //15      // A1 PC1
#define	SPI_MOSI_PIN	A2 //16	// A2 PC2

/** nop to tune soft SPI timing */
#define nop asm volatile ("nop\n\t")

#define  SPI_WAIT  {nop;}

void nokia_spiSetup(void)
{
  setPinMode(SPI_SCK_PIN,  OUTPUT);
  setPinMode(SPI_MISO_PIN, INPUT);
  setPinMode(SPI_MOSI_PIN, OUTPUT);
}


uint8_t nokia_spiRec(void)
{
  uint8_t data = 0;
  // no interrupts during byte receive - about 8 us
  cli();
  // output pin high - like sending 0XFF
  fastDigitalWrite(SPI_MOSI_PIN, HIGH);

  for (uint8_t i = 0; i < 8; i++) {
    fastDigitalWrite(SPI_SCK_PIN, HIGH);

    // adjust so SCK is nice
    nop;
    nop;

    data <<= 1;

    if (fastDigitalRead(SPI_MISO_PIN)) data |= 1;

    fastDigitalWrite(SPI_SCK_PIN, LOW);
  }
  // enable interrupts
  sei();
  return data;
}


void nokia_spiSend(uint8_t data)
{
  // no interrupts during byte send - about 8 us
  cli();
  for (uint8_t i = 0; i < 8; i++) {
    fastDigitalWrite(SPI_SCK_PIN, LOW);
    SPI_WAIT;

    fastDigitalWrite(SPI_MOSI_PIN, data & 0X80);
    SPI_WAIT;

    data <<= 1;

    fastDigitalWrite(SPI_SCK_PIN, HIGH);
    SPI_WAIT;
  }
  // hold SCK high for a few ns
  nop;
  nop;
  nop;
  nop;

  fastDigitalWrite(SPI_SCK_PIN, LOW);
  // enable interrupts
  sei();
}

The examples Nick provides for SPI slave mode are much tidier than mine.

Cheers,

Jack