c++/lpt-signal-generator/lpt.cpp
author František Kučera <franta-hg@frantovo.cz>
Fri, 15 May 2020 20:32:37 +0200
changeset 59 d6614ad97bed
parent 53 516358e07f9d
permissions -rw-r--r--
LV2: modul zesilovače, dle oficiálního příkladu, ale bez závislosti na Pythonu – stačí gcc a make
     1 /**
     2  * LPT signal generator
     3  * Copyright © 2017 František Kučera (frantovo.cz)
     4  *
     5  * This program is free software: you can redistribute it and/or modify
     6  * it under the terms of the GNU General Public License as published by
     7  * the Free Software Foundation, either version 3 of the License, or
     8  * (at your option) any later version.
     9  *
    10  * This program is distributed in the hope that it will be useful,
    11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
    12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    13  * GNU General Public License for more details.
    14  *
    15  * You should have received a copy of the GNU General Public License
    16  * along with this program. If not, see <http://www.gnu.org/licenses/>.
    17  */
    18 
    19 #include <stdlib.h>
    20 #include <iostream>
    21 #include <stdio.h>
    22 #include <math.h>
    23 #include <sys/io.h>
    24 #include <unistd.h>
    25 #include <chrono> // requires -std=c++11
    26 
    27 /**
    28  * can not mix printf and wprintf
    29  * see https://stackoverflow.com/questions/8681623/printf-and-wprintf-in-single-c-code
    30  * > This is to be expected; your code is invoking undefined behavior.
    31  * > Per the C standard, each FILE stream has associated with it an "orientation" (either "byte" or "wide)
    32  * > which is set by the first operation performed on it, and which can be inspected with the fwide function.
    33  * > Calling any function whose orientation conflicts with the orientation of the stream results in undefined behavior.
    34  */
    35 #include <wchar.h>
    36 #include <locale.h>
    37 
    38 
    39 using namespace std;
    40 
    41 // TODO: data types revision
    42 // TODO: time units s, μs, ns – naming convention / unification
    43 
    44 /**
    45  * generates square wave signal on a parallel port pin with given frequency and duty cycle
    46  * mode info: https://blog.frantovo.cz/c/358/Paraleln%C3%AD%20port%20jako%20gener%C3%A1tor%20sign%C3%A1lu
    47  */
    48 int main() {
    49 	//cout << "LPT!" << endl; // same as using printf → breaks all folllowing wprintf() calls, see note above
    50 
    51 	/*
    52 	 * if setlocale() is missing, unicode characters are replaced with ? or „→“ with „->“ because C/POSIX locale is used, 
    53 	 * see man setlocale:
    54 	 * > On startup of the main program, the portable "C" locale is selected as default.
    55 	 * > If locale is an empty string, "", each part of the locale that should be modified is set according to the environment variables.
    56 	 */
    57 	setlocale(LC_ALL,"");
    58 
    59 
    60 	// configuration ----
    61 	int addr = 0xe400; // parallel port address; first number of given port in: cat /proc/ioports | grep parport
    62 	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
    63 	int outputPower = 20; // duty cycle; 100 = 100 %
    64 	int duration = 1; // in seconds; total sleep time, see note above
    65 	// ------------------
    66 
    67 
    68 	int valueWidth =  10; // just for padding of printed values
    69 	int labelWidth = -15; // just for padding of printed labels
    70 
    71 	// ' = thousand separator
    72 	// * = padding
    73 	wprintf(L"%*ls %*x\n", labelWidth, L"Parallel port:", valueWidth, addr); // or %#*x – adds 0x prefix
    74 	wprintf(L"%*ls %'*d Hz\n", labelWidth, L"Base frequency:", valueWidth, baseFreq);
    75 	wprintf(L"%*ls %*d %% duty cycle\n",  labelWidth, L"Output power:", valueWidth, outputPower);
    76 	wprintf(L"%*ls %'*d s\n", labelWidth, L"Duration:", valueWidth, duration);
    77 
    78 	// in microseconds:
    79 	auto oneSecond = 1000 * 1000;
    80 	auto timeOn =  oneSecond *        outputPower  / 100 / baseFreq;
    81 	auto timeOff = oneSecond * (100 - outputPower) / 100 / baseFreq;
    82 
    83 	auto cycleCount = duration * baseFreq;
    84 	wprintf(L"%*ls %'*d ×\n", labelWidth, L"Cycle count:", valueWidth, cycleCount);
    85 	wprintf(L"%*ls %'*d μs 1× in each cycle\n", labelWidth, L"Time on:",  valueWidth, timeOn);
    86 	wprintf(L"%*ls %'*d μs 1× in each cycle\n", labelWidth, L"Time off:", valueWidth, timeOff);
    87 
    88 	//wprintf(L"%*ls %*ls\n", labelWidth, L"unicode test:", valueWidth, L"čeština → …");
    89 
    90 	wprintf(L"\n");
    91 
    92 	// TODO: test whether this address is an parallel port
    93 	if (ioperm(addr,1,1)) { fwprintf(stderr, L"Access denied to port %#x\n", addr), exit(1); }
    94 
    95 
    96 	// calibration
    97 	auto startTimestamp = chrono::high_resolution_clock::now();
    98 	auto calibrationCycles = 10000;
    99 	auto calibrationSleepTime = 10;
   100 
   101 	for (auto i = calibrationCycles; i > 0; i--) {
   102 		outb(0b00000000, addr);
   103 		usleep(calibrationSleepTime);
   104 		outb(0b00000000, addr);
   105 		usleep(calibrationSleepTime);
   106 	}
   107 
   108 	auto finishTimestamp = chrono::high_resolution_clock::now();
   109 	auto measuredDuration = chrono::duration_cast<chrono::nanoseconds>(finishTimestamp - startTimestamp).count();
   110 
   111 	auto singleOutbCostNano = (measuredDuration - calibrationCycles*2*calibrationSleepTime*1000)/calibrationCycles/2;
   112 	auto singleOutbCostMicro = singleOutbCostNano/1000;
   113 
   114 	wprintf(L"%*ls %'*d μs 2× in each calibration cycle\n", labelWidth, L"Single outb():", valueWidth, singleOutbCostMicro);
   115 	wprintf(L"%*ls %'*d ns 2× in each calibration cycle\n", labelWidth, L"Single outb():", valueWidth, singleOutbCostNano);
   116 
   117 	auto minPower = 100*singleOutbCostNano/(1000*1000*1000/baseFreq);
   118 	auto maxPower = 100-minPower;
   119 	wprintf(L"%*ls %*d %% feasible duty cycle\n",  labelWidth, L"Minimum power:", valueWidth, minPower);
   120 	wprintf(L"%*ls %*d %% feasible duty cycle\n",  labelWidth, L"Maximum power:", valueWidth, maxPower);
   121 
   122 	if (singleOutbCostMicro < timeOn && singleOutbCostMicro < timeOff) {
   123 		wprintf(L"%*ls %*ls both frequency and duty cycle should be correct\n",  labelWidth, L"Calibration:", valueWidth, L"OK");
   124 		timeOn  -= singleOutbCostMicro;
   125 		timeOff -= singleOutbCostMicro;
   126 	} else if (2*singleOutbCostMicro < (timeOn + timeOff)) {
   127 		wprintf(L"%*ls %*ls frequency should be OK, but duty cycle is not feasible\n",  labelWidth, L"Calibration:", valueWidth, L"WARNING");
   128 		timeOn  -= singleOutbCostMicro;
   129 		timeOff -= singleOutbCostMicro;
   130 
   131 		if (timeOn < 0) {
   132 			timeOff -= timeOn;
   133 			timeOn = 0;
   134 		} else {
   135 			timeOn -= timeOff;
   136 			timeOff = 0;
   137 		}
   138 	} else {
   139 		wprintf(L"%*ls %*ls both frequency and duty cycle are not feasible\n",  labelWidth, L"Calibration:", valueWidth, L"ERROR");
   140 		timeOn  = 0;
   141 		timeOff = 0;
   142 	}
   143 
   144 	wprintf(L"%*ls %'*d μs 1× in each cycle\n", labelWidth, L"Sleep on:",  valueWidth, timeOn);
   145 	wprintf(L"%*ls %'*d μs 1× in each cycle\n", labelWidth, L"Sleep off:", valueWidth, timeOff);
   146 
   147 	wprintf(L"\n");
   148 
   149 
   150 	// actual signal generation
   151 	startTimestamp = chrono::high_resolution_clock::now();
   152 
   153 	for (auto i = cycleCount; i > 0;  i--) {
   154 		outb(0b00000001, addr); // first data out pin = data out 0 = pin 2 on DB-25 connector
   155 		usleep(timeOn);
   156 		outb(0b00000000, addr);
   157 		usleep(timeOff);
   158 	}
   159 
   160 	finishTimestamp = chrono::high_resolution_clock::now();
   161 	measuredDuration = chrono::duration_cast<chrono::nanoseconds>(finishTimestamp - startTimestamp).count();
   162 
   163 	wprintf(L"%*ls %'*d μs in total\n", labelWidth, L"Deviation:", valueWidth, (measuredDuration-duration*oneSecond*1000)/1000);
   164 	wprintf(L"%*ls %'*d ns in each cycle\n", labelWidth, L"Deviation:", valueWidth, (measuredDuration-duration*oneSecond*1000)/cycleCount);
   165 
   166 }