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
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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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// TODO: data types revision
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// TODO: time units s, μs, ns – naming convention / unification
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/**
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 * generates square wave signal on a parallel port pin with given frequency and duty cycle
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 * mode info: https://blog.frantovo.cz/c/358/Paraleln%C3%AD%20port%20jako%20gener%C3%A1tor%20sign%C3%A1lu
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 */
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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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	// configuration ----
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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 = 20; // duty cycle; 100 = 100 %
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	int duration = 1; // in seconds; total sleep time, see note above
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	// ------------------
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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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	auto oneSecond = 1000 * 1000;
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	auto timeOn =  oneSecond *        outputPower  / 100 / baseFreq;
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	auto timeOff = oneSecond * (100 - outputPower) / 100 / baseFreq;
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	auto 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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	wprintf(L"\n");
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	// TODO: test whether this address is an parallel port
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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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	// calibration
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	auto startTimestamp = chrono::high_resolution_clock::now();
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	auto calibrationCycles = 10000;
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	auto calibrationSleepTime = 10;
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	for (auto i = calibrationCycles; i > 0; i--) {
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		outb(0b00000000, addr);
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		usleep(calibrationSleepTime);
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		outb(0b00000000, addr);
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		usleep(calibrationSleepTime);
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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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	auto singleOutbCostNano = (measuredDuration - calibrationCycles*2*calibrationSleepTime*1000)/calibrationCycles/2;
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	auto singleOutbCostMicro = singleOutbCostNano/1000;
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	wprintf(L"%*ls %'*d μs 2× in each calibration cycle\n", labelWidth, L"Single outb():", valueWidth, singleOutbCostMicro);
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	wprintf(L"%*ls %'*d ns 2× in each calibration cycle\n", labelWidth, L"Single outb():", valueWidth, singleOutbCostNano);
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	auto minPower = 100*singleOutbCostNano/(1000*1000*1000/baseFreq);
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	auto maxPower = 100-minPower;
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	wprintf(L"%*ls %*d %% feasible duty cycle\n",  labelWidth, L"Minimum power:", valueWidth, minPower);
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	wprintf(L"%*ls %*d %% feasible duty cycle\n",  labelWidth, L"Maximum power:", valueWidth, maxPower);
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	if (singleOutbCostMicro < timeOn && singleOutbCostMicro < timeOff) {
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		wprintf(L"%*ls %*ls both frequency and duty cycle should be correct\n",  labelWidth, L"Calibration:", valueWidth, L"OK");
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		timeOn  -= singleOutbCostMicro;
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		timeOff -= singleOutbCostMicro;
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	} else if (2*singleOutbCostMicro < (timeOn + timeOff)) {
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		wprintf(L"%*ls %*ls frequency should be OK, but duty cycle is not feasible\n",  labelWidth, L"Calibration:", valueWidth, L"WARNING");
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		timeOn  -= singleOutbCostMicro;
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		timeOff -= singleOutbCostMicro;
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		if (timeOn < 0) {
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			timeOff -= timeOn;
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			timeOn = 0;
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		} else {
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			timeOn -= timeOff;
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			timeOff = 0;
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		}
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	} else {
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		wprintf(L"%*ls %*ls both frequency and duty cycle are not feasible\n",  labelWidth, L"Calibration:", valueWidth, L"ERROR");
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		timeOn  = 0;
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		timeOff = 0;
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	}
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	wprintf(L"%*ls %'*d μs 1× in each cycle\n", labelWidth, L"Sleep on:",  valueWidth, timeOn);
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	wprintf(L"%*ls %'*d μs 1× in each cycle\n", labelWidth, L"Sleep off:", valueWidth, timeOff);
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	wprintf(L"\n");
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	// actual signal generation
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	startTimestamp = chrono::high_resolution_clock::now();
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	for (auto i = cycleCount; i > 0;  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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	finishTimestamp = chrono::high_resolution_clock::now();
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	measuredDuration = chrono::duration_cast<chrono::nanoseconds>(finishTimestamp - startTimestamp).count();
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	wprintf(L"%*ls %'*d μs in total\n", labelWidth, L"Deviation:", valueWidth, (measuredDuration-duration*oneSecond*1000)/1000);
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	wprintf(L"%*ls %'*d ns in each cycle\n", labelWidth, L"Deviation:", valueWidth, (measuredDuration-duration*oneSecond*1000)/cycleCount);
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}