Différences

Ci-dessous, les différences entre deux révisions de la page.

--- diy:projets:tl_partieemetteur [2018/05/26 14:22] – [Interface avec le gpio] sdurand
+++ diy:projets:tl_partieemetteur [2018/07/02 09:34] (Version actuelle) – [Le programme principal et la fonction qui gère la led] sdurand
@@ Ligne 53: / Ligne 53: @@
 **effectuer toutes les opérations** dont je viens de vous parler, c'est comme ça que je vous recommande de procéder.
 J'ai personnellement choisi de **créer une classe** pour encapsuler ces opérations. Le code de cette classe est
-disponible sur [[https://github.com/SDurand7/LedTransmitter|mon github]] (fichiers ledcontroller.cpp/hpp) au cas où vous ne souhaiteriez pas
+disponible ci-dessous au cas où vous ne souhaiteriez pas
 tout réécrire vous même.
@@ Ligne 183: / Ligne 183: @@
 ===== Sources du projet =====
-La totalité des sources de cette partie du projet sont disponibles à [[https://github.com/SDurand7/LedTransmitter|cette addresse]].
+==== La classe pour contrôler le gpio ====
-Je vous invite à consulter le guide de la partie récepteur de Gauthier pour récupérer les sources
-correspondantes.
+<code C++>
+#include "ledcontroller.hpp"
+// Private method that export the choosen gpio
+void LedController::export_gpio() {
+	std::ofstream exportFile("/sys/class/gpio/export");
+	if(!exportFile.is_open()) {
+		std::cerr << "ERROR: Could not export gpio " << this->numero << "." << std::endl;
+		throw ERR_EXPORT;
+	}
+	exportFile << this->numero;
+	exportFile.close();
+}
+// Private method that unexport the previously opened gpio
+void LedController::unexport_gpio() {
+	std::ofstream unexportFile("/sys/class/gpio/unexport");
+	if(!unexportFile.is_open()) {
+		std::cerr << "ERROR: Could not unexport gpio " << this->numero << "." << std::endl;
+		throw ERR_UNEXPORT;
+	}
+	unexportFile << this->numero;
+	unexportFile.close();
+}
+// Constructor of our class:
+// numero: numero of the gpio's pin we want to open
+// dirOut: boolean indicating if the direction we want is out or not (as it is a LedController, it is set to true by default)
+// litUp: boolean indicating if the led should be initially on or off
+LedController::LedController(int numero, bool dirOut, bool litUp) {
+	this->numero = numero;
+	export_gpio();
+	// Adding a little delay to make sure that the files created when exporting exists before we start working on them
+	std::this_thread::sleep_for(std::chrono::milliseconds(EXPORT_DELAY));
+	std::ofstream directionFile(std::string("/sys/class/gpio/gpio" + std::to_string(numero) + "/direction").c_str());
+	if(!directionFile.is_open()) {
+		unexport_gpio();
+		std::cerr << "ERROR: Could not open \"direction\" for gpio " << numero << "." << std::endl;
+		throw ERR_EXPORT;
+	}
+	// Setting the direction according to the boolean dirOut
+	directionFile << (dirOut ? "out" : "in");
+	directionFile.close();
+	if(!litUp) {
+		turnOff();
+	}
+	else {
+		turnOn();
+	}
+}
+// Destructor that will unexport the gpio previously opened
+LedController::~LedController() {
+	unexport_gpio();
+}
+// Public method lighting up the led
+void LedController::turnOn() {
+	std::ofstream value;
+	value.open(std::string("/sys/class/gpio/gpio" + std::to_string(this->numero) + "/value").c_str());
+	if(!value.is_open()) {
+		unexport_gpio();
+		std::cerr << "ERROR: Could not open \"value\" for gpio " << this->numero << "." << std::endl;
+		throw ERR_VALUE;
+	}
+	value << "0";
+	value.close();
+}
+// Public method turning off the led
+void LedController::turnOff() {
+	std::ofstream value;
+	value.open(std::string("/sys/class/gpio/gpio" + std::to_string(this->numero) + "/value").c_str());
+	if(!value.is_open()) {
+		unexport_gpio();
+		std::cerr << "ERROR: Could not open \"value\" for gpio " << this->numero << "." << std::endl;
+		throw ERR_VALUE;
+	}
+	value << "1";
+	value.close();
+}
+</code>
+==== Son header ====
+<code C++>
+#ifndef LEDCONTROLLER_HPP
+#define LEDCONTROLLER_HPP
+#include <iostream>
+#include <string>
+#include <chrono>
+#include <thread>
+#include <fstream>
+// Refer to the constructor source code for more info on this define
+#define EXPORT_DELAY 400
+// A few define to make errors handling clearer
+#define ERR_EXPORT -2
+#define ERR_UNEXPORT -3
+#define ERR_VALUE -4
+#define ERR_DIRECTION -5
+class LedController {
+	public:
+		LedController(int numero, bool dirOut = true, bool litUp = false);
+		~LedController();
+		void turnOn();
+		void turnOff();
+	private:
+		void export_gpio();
+		void unexport_gpio();
+		int numero;
+};
+#endif
+</code>
+==== Le programme principal et la fonction qui gère la led ====
+<code C++>
+#include <iostream>
+#include <string>
+#include <chrono>
+#include <thread>
+#include "ledcontroller.hpp"
+#define GPIO_PIN 21
+#define BITRATE 20
+#define BITTIME static_cast<int>(1e6/BITRATE)
+#define ALL_GOOD 0
+const auto time_step = std::chrono::microseconds(BITTIME);
+// We are asuming here that a char is always an octet, and we will assume in every part of the code
+const unsigned char powers_of_two[8] = {128, 64, 32, 16, 8, 4, 2, 1};
+// Function that iterates over message and switch on and off the led of lc according to the bits
+void transmit(LedController& lc, const std::string& message) {
+	// Initializing timer as the reference time
+	auto timer = std::chrono::high_resolution_clock::now();
+	// Turning on the light to tell the receptor we're starting to emit
+	lc.turnOn();
+	// Iterating over the message
+	for(const char& c: message) {
+		// Iterating over the bits of c (again, we're assuming that a char is an octet long)
+		for(unsigned int i = 0; i < 8; i++) {
+			// Incrementing the timer, computing wether we should lightUp the led or not, and sleeping until it's time to change the state of the led
+			timer += time_step;
+			const bool lightUp = c & powers_of_two[i];
+			std::this_thread::sleep_until(timer);
+			lightUp ? lc.turnOn() : lc.turnOff();
+		}
+	}
+	std::this_thread::sleep_until(timer + time_step);
+	lc.turnOff();
+	// Sleeping long enough to make sure that the receptor received at least a full octet of zeros (it will mark the end of transmission for it)
+	std::this_thread::sleep_for(2 * time_step);
+}
+// This main simply get the input from stdin and act in consequence
+int main() {
+	LedController lc(GPIO_PIN);
+	std::string message;
+	// Getting the first string
+	std::cout << "Waiting for a string to send: (\"/test\" to launch a sequence of 0 and 1, \"/end\" to end the program)" << std::endl;
+	std::getline(std::cin, message);
+	// Sending message if it is different of "/end" and "/test"
+	// "/end" will end the loop and therefore, the execution
+	while(message != "/end") {
+		// I feel like it's ok to not use a switch because I don't plan to add more commands, but if you plan to, you should definitely use one
+		if(message == "/test") {
+			// The test sequence is a sequence of upper case "u" because in ASCII, an U is 01010101, and this makes a pretty good test sequence
+			transmit(lc, "UUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUU");
+		}
+		else {
+			transmit(lc, message);
+		}
+		std::cout << "Transfer complete.\n" << std::endl;
+		std::cout << "Waiting for a string to send: " << std::endl;
+		std::getline(std::cin, message);
+	}
+	return ALL_GOOD;
+}
+</code>
 ----
-//Auteur: Sylvain Durand//
+//Auteur: S. Durand//