c++/lpt-signal-generator/lpt.cpp
author František Kučera <franta-hg@frantovo.cz>
Fri, 09 Jun 2017 23:23:25 +0200
changeset 47 9e2addbb9674
parent 46 616e71c2d754
child 48 254d5d1bc659
permissions -rw-r--r--
lpt-signal-generator: Makefile
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/**
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 * LPT signal generator
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 * Copyright © 2017 František Kučera (frantovo.cz)
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 *
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 * This program is free software: you can redistribute it and/or modify
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 * it under the terms of the GNU General Public License as published by
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 * the Free Software Foundation, either version 3 of the License, or
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 * (at your option) any later version.
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 *
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 * This program is distributed in the hope that it will be useful,
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 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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 * GNU General Public License for more details.
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 *
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 * You should have received a copy of the GNU General Public License
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 * along with this program. If not, see <http://www.gnu.org/licenses/>.
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 */
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#include <stdlib.h>
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#include <iostream>
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#include <stdio.h>
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#include <math.h>
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#include <sys/io.h>
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#include <unistd.h>
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#include <chrono> // requires -std=c++11
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/**
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 * can not mix printf and wprintf
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 * see https://stackoverflow.com/questions/8681623/printf-and-wprintf-in-single-c-code
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 * > This is to be expected; your code is invoking undefined behavior.
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 * > Per the C standard, each FILE stream has associated with it an "orientation" (either "byte" or "wide)
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 * > which is set by the first operation performed on it, and which can be inspected with the fwide function.
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 * > Calling any function whose orientation conflicts with the orientation of the stream results in undefined behavior.
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 */
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#include <wchar.h>
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#include <locale.h>
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using namespace std;
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// run this program: make run
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// depending on frequency and machine performance the total time will be more than given duration
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// despite the real-time priority, because some additional time is spent in outb() functions
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// so "duration" means total sleep time
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int main() {
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  //cout << "LPT!" << endl; // same as using printf → breaks all folllowing wprintf() calls, see note above
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  /*
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   * if setlocale() is missing, unicode characters are replaced with ? or „→“ with „->“ because C/POSIX locale is used, 
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   * see man setlocale:
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   * > On startup of the main program, the portable "C" locale is selected as default.
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   * > If locale is an empty string, "", each part of the locale that should be modified is set according to the environment variables.
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   */
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  setlocale(LC_ALL,"");
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  int addr = 0xe400; // parallel port address; first number of given port in: cat /proc/ioports | grep parport
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  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
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  int outputPower = 10; // duty cycle; 100 = 100 %
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  int duration = 1; // in seconds; total sleep time, see note above
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  int valueWidth =  10; // just for padding of printed values
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  int labelWidth = -15; // just for padding of printed labels
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  // ' = thousand separator
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  // * = padding
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  wprintf(L"%*ls %*x\n", labelWidth, L"Parallel port:", valueWidth, addr); // or %#*x – adds 0x prefix
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  wprintf(L"%*ls %'*d Hz\n", labelWidth, L"Base frequency:", valueWidth, baseFreq);
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  wprintf(L"%*ls %*d %% duty cycle\n",  labelWidth, L"Output power:", valueWidth, outputPower);
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  wprintf(L"%*ls %'*d s\n", labelWidth, L"Duration:", valueWidth, duration);
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  // in microseconds:
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  int oneSecond = 1000 * 1000;
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  int timeOn =  oneSecond *        outputPower  / 100 / baseFreq;
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  int timeOff = oneSecond * (100 - outputPower) / 100 / baseFreq;
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  int cycleCount = duration * baseFreq;
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  wprintf(L"%*ls %'*d ×\n", labelWidth, L"Cycle count:", valueWidth, cycleCount);
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  wprintf(L"%*ls %'*d μs 1× in each cycle\n", labelWidth, L"Time on:",  valueWidth, timeOn);
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  wprintf(L"%*ls %'*d μs 1× in each cycle\n", labelWidth, L"Time off:", valueWidth, timeOff);
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  //wprintf(L"%*ls %*ls\n", labelWidth, L"unicode test:", valueWidth, L"čeština → …");
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  if (ioperm(addr,1,1)) { fwprintf(stderr, L"Access denied to port %#x\n", addr), exit(1); }
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  outb(0b00000000, addr);
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  auto startTimestamp = chrono::high_resolution_clock::now();
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  for (int i = 0; i < cycleCount; i++) {
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    outb(0b00000001, addr); // first data out pin = data out 0 = pin 2 on DB-25 connector
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    usleep(timeOn);
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    outb(0b00000000, addr);
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    usleep(timeOff);
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  }
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  auto finishTimestamp = chrono::high_resolution_clock::now();
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  auto measuredDuration = chrono::duration_cast<chrono::nanoseconds>(finishTimestamp - startTimestamp).count();
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  wprintf(L"%*ls %'*d μs 2× in each cycle\n", labelWidth, L"single outb():", valueWidth, (measuredDuration-duration*oneSecond*1000)/cycleCount/2/1000);
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  wprintf(L"%*ls %'*d ns 2× in each cycle\n", labelWidth, L"single outb():", valueWidth, (measuredDuration-duration*oneSecond*1000)/cycleCount/2);
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}