/**

 * LPT signal generator

 * Copyright © 2017 František Kučera (frantovo.cz)

 *

 * This program is free software: you can redistribute it and/or modify

 * it under the terms of the GNU General Public License as published by

 * the Free Software Foundation, either version 3 of the License, or

 * (at your option) any later version.

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the

 * GNU General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program. If not, see <http://www.gnu.org/licenses/>.

 */

#include <stdlib.h>

#include <iostream>

#include <stdio.h>

#include <math.h>

#include <sys/io.h>

#include <unistd.h>

#include <chrono> // requires -std=c++11

/**

 * can not mix printf and wprintf

 * see https://stackoverflow.com/questions/8681623/printf-and-wprintf-in-single-c-code

 * > This is to be expected; your code is invoking undefined behavior.

 * > Per the C standard, each FILE stream has associated with it an "orientation" (either "byte" or "wide)

 * > which is set by the first operation performed on it, and which can be inspected with the fwide function.

 * > Calling any function whose orientation conflicts with the orientation of the stream results in undefined behavior.

 */

#include <wchar.h>

#include <locale.h>

using namespace std;

// run this program: make run

// depending on frequency and machine performance the total time will be more than given duration

// despite the real-time priority, because some additional time is spent in outb() functions

// so "duration" means total sleep time

// TODO: data types revision

// TODO: time units s, μs, ns – naming convention / unification

/**

 * generates square wave signal on a parallel port pin with given frequency and duty cycle

 * mode info: https://blog.frantovo.cz/c/358/Paraleln%C3%AD%20port%20jako%20gener%C3%A1tor%20sign%C3%A1lu

 */

int main() {

  //cout << "LPT!" << endl; // same as using printf → breaks all folllowing wprintf() calls, see note above

  /*

   * if setlocale() is missing, unicode characters are replaced with ? or „→“ with „->“ because C/POSIX locale is used, 

   * see man setlocale:

   * > On startup of the main program, the portable "C" locale is selected as default.

   * > If locale is an empty string, "", each part of the locale that should be modified is set according to the environment variables.

   */

  setlocale(LC_ALL,"");

  // configuration ----

  int addr = 0xe400; // parallel port address; first number of given port in: cat /proc/ioports | grep parport

  int baseFreq = 10000; // base frequency in Hz, should be between 5 000 between 10 000 Hz; lower frequency leads to dashed/dotted lines instead of greyscale

  int outputPower = 20; // duty cycle; 100 = 100 %

  int duration = 1; // in seconds; total sleep time, see note above

  // ------------------

  int valueWidth =  10; // just for padding of printed values

  int labelWidth = -15; // just for padding of printed labels

  // ' = thousand separator

  // * = padding

  wprintf(L"%*ls %*x\n", labelWidth, L"Parallel port:", valueWidth, addr); // or %#*x – adds 0x prefix

  wprintf(L"%*ls %'*d Hz\n", labelWidth, L"Base frequency:", valueWidth, baseFreq);

  wprintf(L"%*ls %*d %% duty cycle\n",  labelWidth, L"Output power:", valueWidth, outputPower);

  wprintf(L"%*ls %'*d s\n", labelWidth, L"Duration:", valueWidth, duration);

  // in microseconds:

  auto oneSecond = 1000 * 1000;

  auto timeOn =  oneSecond *        outputPower  / 100 / baseFreq;

  auto timeOff = oneSecond * (100 - outputPower) / 100 / baseFreq;

  auto cycleCount = duration * baseFreq;

  wprintf(L"%*ls %'*d ×\n", labelWidth, L"Cycle count:", valueWidth, cycleCount);

  wprintf(L"%*ls %'*d μs 1× in each cycle\n", labelWidth, L"Time on:",  valueWidth, timeOn);

  wprintf(L"%*ls %'*d μs 1× in each cycle\n", labelWidth, L"Time off:", valueWidth, timeOff);

  //wprintf(L"%*ls %*ls\n", labelWidth, L"unicode test:", valueWidth, L"čeština → …");

  wprintf(L"\n");

  // TODO: test whether this address is an parallel port

  if (ioperm(addr,1,1)) { fwprintf(stderr, L"Access denied to port %#x\n", addr), exit(1); }

  // calibration

  auto startTimestamp = chrono::high_resolution_clock::now();

  auto calibrationCycles = 10000;

  auto calibrationSleepTime = 10;

  for (auto i = calibrationCycles; i > 0; i--) {

    outb(0b00000000, addr);

    usleep(calibrationSleepTime);

    outb(0b00000000, addr);

    usleep(calibrationSleepTime);

  }

  auto finishTimestamp = chrono::high_resolution_clock::now();

  auto measuredDuration = chrono::duration_cast<chrono::nanoseconds>(finishTimestamp - startTimestamp).count();

  auto singleOutbCostNano = (measuredDuration - calibrationCycles*2*calibrationSleepTime*1000)/calibrationCycles/2;

  auto singleOutbCostMicro = singleOutbCostNano/1000;

  wprintf(L"%*ls %'*d μs 2× in each calibration cycle\n", labelWidth, L"Single outb():", valueWidth, singleOutbCostMicro);

  wprintf(L"%*ls %'*d ns 2× in each calibration cycle\n", labelWidth, L"Single outb():", valueWidth, singleOutbCostNano);

  auto minPower = 100*singleOutbCostNano/(1000*1000*1000/baseFreq);

  auto maxPower = 100-minPower;

  wprintf(L"%*ls %*d %% feasible duty cycle\n",  labelWidth, L"Minimum power:", valueWidth, minPower);

  wprintf(L"%*ls %*d %% feasible duty cycle\n",  labelWidth, L"Maximum power:", valueWidth, maxPower);

  if (singleOutbCostMicro < timeOn && singleOutbCostMicro < timeOff) {

    wprintf(L"%*ls %*ls both frequency and duty cycle should be correct\n",  labelWidth, L"Calibration:", valueWidth, L"OK");

    timeOn  -= singleOutbCostMicro;

    timeOff -= singleOutbCostMicro;

  } else if (2*singleOutbCostMicro < (timeOn + timeOff)) {

    wprintf(L"%*ls %*ls frequency should be OK, but duty cycle is not feasible\n",  labelWidth, L"Calibration:", valueWidth, L"WARNING");

    timeOn  -= singleOutbCostMicro;

    timeOff -= singleOutbCostMicro;

    if (timeOn < 0) {

      timeOff -= timeOn;

      timeOn = 0;

    } else {

      timeOn -= timeOff;

      timeOff = 0;

    }

  } else {

    wprintf(L"%*ls %*ls both frequency and duty cycle are not feasible\n",  labelWidth, L"Calibration:", valueWidth, L"ERROR");

    timeOn  = 0;

    timeOff = 0;

  }

  wprintf(L"%*ls %'*d μs 1× in each cycle\n", labelWidth, L"Sleep on:",  valueWidth, timeOn);

  wprintf(L"%*ls %'*d μs 1× in each cycle\n", labelWidth, L"Sleep off:", valueWidth, timeOff);

  wprintf(L"\n");

  // actual signal generation

  startTimestamp = chrono::high_resolution_clock::now();

  for (auto i = cycleCount; i > 0;  i--) {

    outb(0b00000001, addr); // first data out pin = data out 0 = pin 2 on DB-25 connector

    usleep(timeOn);

    outb(0b00000000, addr);

    usleep(timeOff);

  }

  finishTimestamp = chrono::high_resolution_clock::now();

  measuredDuration = chrono::duration_cast<chrono::nanoseconds>(finishTimestamp - startTimestamp).count();

  wprintf(L"%*ls %'*d μs in total\n", labelWidth, L"Deviation:", valueWidth, (measuredDuration-duration*oneSecond*1000)/1000);

  wprintf(L"%*ls %'*d ns in each cycle\n", labelWidth, L"Deviation:", valueWidth, (measuredDuration-duration*oneSecond*1000)/cycleCount);

}