#include <SPI.h>

// similar to variables used in TFT library
volatile uint8_t *csport, *rsport;
uint8_t cspinmask, rspinmask;

void setup() {
  SPI.begin();
  Serial.begin(9600);
  SPI.setClockDivider(SPI_CLOCK_DIV2);

  while (!Serial)
    ;
  delay(1000);
  
  Serial.println();
  Serial.print("                                       Plain SPI:     ");
  test_no_transaction();
  Serial.println();

#if defined(SPI_HAS_TRANSACTION)

  Serial.print("Transaction API (interrupts not used): (TFT estimate) ");
  test_transaction_TFT();
  Serial.println();

  // Uncomment to check interrupt-based API
  SPI.usingInterrupt(0);

  // Uncomment to check event-based API
  //SPI.onBeginEvent(beginEvent);
  //SPI.onEndEvent(endEvent);

  Serial.print("Transaction API    (using interrupts): (TFT estimate) ");
  test_transaction_TFT();
  Serial.println();
#endif

  csport = &PORTC;
  rsport = &PORTC;
  cspinmask = 1;
  rspinmask = 2;
}

boolean interruptSave;

void beginEvent() {
  interruptSave = interruptsStatus();
  noInterrupts();
}

void endEvent() {
  if (interruptSave) interrupts();
}

void loop() {
}



void writecommand(byte cmd) {
  *rsport &= ~rspinmask;
  *csport &= ~cspinmask;
  SPI.transfer(cmd);
  *csport |= cspinmask;
}
void writedata(byte cmd) {
  *rsport |=  rspinmask;
  *csport &= ~cspinmask;
  SPI.transfer(cmd);
  *csport |= cspinmask;
}


void test_transaction_TFT() {
  uint32_t start = millis();
  for (int i = 0; i < 30000; i++) {
    // emulate setAddrWindow() -- 11 SPI transfers
    SPI.beginTransaction(SPI_CLOCK_8000000, MSBFIRST, SPI_MODE0);
    writecommand(0xff);
    writedata(0xff);
    writedata(0xff);
    writedata(0xff);
    writedata(0xff);
    writecommand(0xff);
    writedata(0xff);
    writedata(0xff);
    writedata(0xff);
    writedata(0xff);
    writecommand(0xff);
    SPI.endTransaction();

    SPI.beginTransaction(SPI_CLOCK_8000000, MSBFIRST, SPI_MODE0);
    *rsport |=  rspinmask;
    *csport &= ~cspinmask;
    SPI.transfer(0xff);
    SPI.transfer(0xff);
    *csport |= cspinmask;
    SPI.endTransaction();
  }
  uint32_t delta = millis() - start;
  float loopsPerSec = 1000.0 / delta * 30000.0;
  float throughput = loopsPerSec * 13 * 8;
  Serial.print(throughput);
}

void test_no_transaction() {
  uint32_t start = millis();
  for (int i = 0; i < 30000; i++) {
    writecommand(0xff);
    writedata(0xff);
    writedata(0xff);
    writedata(0xff);
    writedata(0xff);
    writecommand(0xff);
    writedata(0xff);
    writedata(0xff);
    writedata(0xff);
    writedata(0xff);
    writecommand(0xff);
    *rsport |=  rspinmask;
    *csport &= ~cspinmask;
    SPI.transfer(0xff);
    SPI.transfer(0xff);
    *csport |= cspinmask;
  }
  uint32_t delta = millis() - start;
  float loopsPerSec = 1000.0 / delta * 30000.0;
  float throughput = loopsPerSec * 13 * 8;
  Serial.print(throughput);
}