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144 lines
4.0 KiB
C++
144 lines
4.0 KiB
C++
// ArduinoJson - arduinojson.org
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// Copyright Benoit Blanchon 2014-2018
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// MIT License
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//
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// This example shows how to store your project configuration in a file.
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// It uses the SD library but can be easily modified for any other file-system.
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//
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// The file contains a JSON document with the following content:
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// {
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// "hostname": "examples.com",
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// "port": 2731
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// }
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#include <ArduinoJson.h>
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#include <SD.h>
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#include <SPI.h>
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// Configuration that we'll store on disk
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struct Config {
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char hostname[64];
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int port;
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};
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const char *filename = "/config.txt"; // <- SD library uses 8.3 filenames
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Config config; // <- global configuration object
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// Loads the configuration from a file
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void loadConfiguration(const char *filename, Config &config) {
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// Open file for reading
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File file = SD.open(filename);
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// Allocate the memory pool on the stack.
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// Don't forget to change the capacity to match your JSON document.
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// Use arduinojson.org/assistant to compute the capacity.
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StaticJsonBuffer<512> jsonBuffer;
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// Parse the root object
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JsonObject &root = jsonBuffer.parseObject(file);
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if (!root.success())
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Serial.println(F("Failed to read file, using default configuration"));
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// Copy values from the JsonObject to the Config
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config.port = root["port"] | 2731;
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strlcpy(config.hostname, // <- destination
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root["hostname"] | "example.com", // <- source
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sizeof(config.hostname)); // <- destination's capacity
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// Close the file (File's destructor doesn't close the file)
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file.close();
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}
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// Saves the configuration to a file
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void saveConfiguration(const char *filename, const Config &config) {
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// Delete existing file, otherwise the configuration is appended to the file
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SD.remove(filename);
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// Open file for writing
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File file = SD.open(filename, FILE_WRITE);
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if (!file) {
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Serial.println(F("Failed to create file"));
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return;
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}
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// Allocate the memory pool on the stack
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// Don't forget to change the capacity to match your JSON document.
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// Use https://arduinojson.org/assistant/ to compute the capacity.
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StaticJsonBuffer<256> jsonBuffer;
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// Parse the root object
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JsonObject &root = jsonBuffer.createObject();
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// Set the values
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root["hostname"] = config.hostname;
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root["port"] = config.port;
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// Serialize JSON to file
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if (root.printTo(file) == 0) {
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Serial.println(F("Failed to write to file"));
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}
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// Close the file (File's destructor doesn't close the file)
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file.close();
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}
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// Prints the content of a file to the Serial
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void printFile(const char *filename) {
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// Open file for reading
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File file = SD.open(filename);
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if (!file) {
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Serial.println(F("Failed to read file"));
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return;
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}
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// Extract each characters by one by one
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while (file.available()) {
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Serial.print((char)file.read());
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}
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Serial.println();
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// Close the file (File's destructor doesn't close the file)
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file.close();
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}
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void setup() {
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// Initialize serial port
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Serial.begin(9600);
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while (!Serial) continue;
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// Initialize SD library
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while (!SD.begin()) {
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Serial.println(F("Failed to initialize SD library"));
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delay(1000);
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}
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// Should load default config if run for the first time
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Serial.println(F("Loading configuration..."));
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loadConfiguration(filename, config);
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// Create configuration file
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Serial.println(F("Saving configuration..."));
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saveConfiguration(filename, config);
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// Dump config file
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Serial.println(F("Print config file..."));
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printFile(filename);
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}
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void loop() {
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// not used in this example
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}
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// See also
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// --------
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//
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// The website arduinojson.org contains the documentation for all the functions
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// used above. It also includes an FAQ that will help you solve any
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// serialization or deserialization problem.
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// Please check it out at: https://arduinojson.org/
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//
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// The book "Mastering ArduinoJson" contains a case study of a project that has
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// a complex configuration with nested members.
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// Contrary to this example, the project in the book uses the SPIFFS filesystem.
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// Please check it out at: https://arduinojson.org/book/
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