c strings everywhere.

ampel-firmware/ampel-firmware.ino

@@ -87,6 +87,10 @@ void setup() {
   Serial.print(F("Board    : "));
   Serial.println(ampel.board);
 
+#ifdef AMPEL_CSV
+  csv_writer::initialize(ampel.sensorId);
+#endif
+
 #ifdef AMPEL_WIFI
   WiFiConnect(ampel.sensorId);
 
@@ -100,7 +104,7 @@ void setup() {
 
     ntp::initialize();
 
-    if (MDNS.begin(ampel.sensorId.c_str())) { // Start the mDNS responder for SENSOR_ID.local
+    if (MDNS.begin(ampel.sensorId)) { // Start the mDNS responder for SENSOR_ID.local
       MDNS.addService("http", "tcp", 80);
       Serial.println(F("mDNS responder started"));
     } else {
@@ -108,15 +112,11 @@ void setup() {
     }
 
 #  ifdef AMPEL_MQTT
-    mqtt::initialize("CO2sensors/" + ampel.sensorId);
+    mqtt::initialize(ampel.sensorId);
 #  endif
   }
 #endif
 
-#ifdef AMPEL_CSV
-  csv_writer::initialize();
-#endif
-
 #if defined(AMPEL_LORAWAN) && defined(ESP32)
   lorawan::initialize();
 #endif

ampel-firmware/co2_sensor.h

@@ -22,7 +22,7 @@ namespace sensor {
   extern uint16_t co2;
   extern float temperature;
   extern float humidity;
-  extern char timestamp[23];
+  extern char timestamp[];
 
   void initialize();
   bool processData();

ampel-firmware/csv_writer.cpp

@@ -78,13 +78,15 @@ namespace csv_writer {
   }
 #endif
 
-  const String filename = "/" + ampel.sensorId + ".csv";
+  char filename[15]; // "/ESPxxxxxx.csv\0"
 
   int getAvailableSpace() {
     return getTotalSpace() - getUsedSpace();
   }
 
-  void initialize() {
+  void initialize(const char *sensorId) {
+    snprintf(filename, sizeof(filename), "/%s.csv", sensorId);
+
     Serial.print(F("Initializing FS..."));
     if (mountFS()) {
       Serial.println(F("done."));
@@ -187,7 +189,7 @@ namespace csv_writer {
       }
       csv_file.close();
     }
-    Serial.println(F("################"));
+    Serial.println(F("######################"));
   }
 
   void formatFilesystem() {

ampel-firmware/csv_writer.h

@@ -20,11 +20,11 @@ namespace config {
   extern uint16_t csv_interval; // [s]
 }
 namespace csv_writer {
-  extern char last_successful_write[23];
-  void initialize();
-  void logIfTimeHasCome(const char* timestamp, const int16_t &co2, const float &temperature, const float &humidity);
+  extern char last_successful_write[];
+  void initialize(const char *sensorId);
+  void logIfTimeHasCome(const char *timestamp, const int16_t &co2, const float &temperature, const float &humidity);
   int getAvailableSpace();
-  extern const String filename;
+  extern char filename[];
 
   void setCSVinterval(int32_t csv_interval);
   void showCSVContent();

ampel-firmware/mqtt.cpp

@@ -23,13 +23,13 @@ namespace mqtt {
   unsigned long last_failed_at = 0;
   bool connected = false;
 
-  String publish_topic;
+  char publish_topic[21]; // e.g. "CO2sensors/ESPxxxxxx\0"
   const char *json_sensor_format;
   char last_successful_publish[23] = "";
 
-  void initialize(String &topic) {
+  void initialize(const char *sensorId) {
     json_sensor_format = PSTR("{\"time\":\"%s\", \"co2\":%d, \"temp\":%.1f, \"rh\":%.1f}");
-    publish_topic = topic;
+    snprintf(publish_topic, sizeof(publish_topic), "CO2sensors/%s", sensorId);
 #if defined(ESP8266)
     espClient.setInsecure(); // Sorry, we don't want to flash the sensors every 3 months.
 #endif
@@ -49,7 +49,7 @@ namespace mqtt {
       char payload[75]; // Should be enough for json...
       snprintf(payload, sizeof(payload), json_sensor_format, timestamp, co2, temperature, humidity);
       // Topic is the same as clientID. e.g. 'CO2sensors/ESP3d03da'
-      if (mqttClient.publish(publish_topic.c_str(), payload)) {
+      if (mqttClient.publish(publish_topic, payload)) {
         Serial.println(F("OK"));
         ntp::getLocalTime(last_successful_publish);
       } else {
@@ -96,7 +96,7 @@ namespace mqtt {
 
     led_effects::onBoardLEDOn();
     // Wait for connection, at most 15s (default)
-    mqttClient.connect(publish_topic.c_str(), config::mqtt_user, config::mqtt_password);
+    mqttClient.connect(publish_topic, config::mqtt_user, config::mqtt_password);
     led_effects::onBoardLEDOff();
 
     connected = mqttClient.connected();
@@ -104,7 +104,7 @@ namespace mqtt {
     if (connected) {
       if (config::allow_mqtt_commands) {
         char control_topic[60]; // Should be enough for "CO2sensors/ESPd03cc5/control"
-        snprintf(control_topic, sizeof(control_topic), "%s/control", publish_topic.c_str());
+        snprintf(control_topic, sizeof(control_topic), "%s/control", publish_topic);
         mqttClient.subscribe(control_topic);
         mqttClient.setCallback(controlSensorCallback);
       }
@@ -153,7 +153,7 @@ namespace mqtt {
   // The sensor will send the info to "CO2sensors/ESP123456/info".
   void sendInfoAboutLocalNetwork() {
     char info_topic[60]; // Should be enough for "CO2sensors/ESP123456/info"
-    snprintf(info_topic, sizeof(info_topic), "%s/info", publish_topic.c_str());
+    snprintf(info_topic, sizeof(info_topic), "%s/info", publish_topic);
 
     char payload[75]; // Should be enough for info json...
     const char *json_info_format = PSTR("{\"local_ip\":\"%s\", \"ssid\":\"%s\"}");

ampel-firmware/mqtt.h

@@ -13,7 +13,7 @@ namespace config {
 namespace mqtt {
   extern char last_successful_publish[];
   extern bool connected;
-  void initialize(String &topic);
+  void initialize(const char *sensorId);
   void keepConnection();
   void publishIfTimeHasCome(const char *timestamp, const int16_t &co2, const float &temp, const float &hum);
 

ampel-firmware/util.cpp

@@ -13,20 +13,6 @@ const char *current_board = "ESP32";
 const char *current_board = "UNKNOWN";
 #endif
 
-// Get last 3 bytes of ESP MAC (worldwide unique)
-String macToID() {
-  uint8_t mac[6];
-  WiFi.macAddress(mac);
-  String result;
-  for (int i = 3; i < 6; i++) {
-    if (mac[i] < 16)
-      result += '0';
-    result += String(mac[i], HEX);
-  }
-  result.toLowerCase();
-  return result;
-}
-
 //NOTE: ESP32 sometimes couldn't access the NTP server, and every loop would take +1000ms
 // ifdefs could be used to define functions specific to ESP32, e.g. with configTime
 namespace ntp {
@@ -70,8 +56,18 @@ void Ampel::showFreeSpace() {
   Serial.println(F(" bytes."));
 }
 
+char sensorId[10]; // e.g "ESPxxxxxx\0"
+
+char* getSensorId() {
+  uint8_t mac[6];
+  WiFi.macAddress(mac);
+  // Get last 3 bytes of ESP MAC (worldwide unique)
+  snprintf(sensorId, sizeof(sensorId), "ESP%02x%02x%02x", mac[3], mac[4], mac[5]);
+  return sensorId;
+}
+
 Ampel::Ampel() :
-    board(current_board), sensorId("ESP" + macToID()), max_loop_duration(0) {
+    board(current_board), sensorId(getSensorId()), max_loop_duration(0) {
   sensor_console::defineIntCommand("set_time", ntp::setLocalTime, F(" 1618829570 (Sets time to the given UNIX time)"));
   sensor_console::defineCommand("free", Ampel::showFreeSpace, F(" (Displays available heap space)"));
   sensor_console::defineCommand("reset", []() {

ampel-firmware/util.h

@@ -37,7 +37,7 @@ private:
   static void showFreeSpace();
 public:
   const char *board;
-  const String sensorId;
+  const char *sensorId;
   uint32_t max_loop_duration;
   Ampel();
 };

ampel-firmware/web_server.cpp

@@ -65,7 +65,7 @@ namespace web_server {
 #ifdef AMPEL_CSV
             "<li class='pure-menu-item'><a href='#graph' class='pure-menu-link'>Graph</a></li>\n"
             "<li class='pure-menu-item'><a href='#log' class='pure-menu-link'>Log</a></li>\n"
-            "<li class='pure-menu-item'><a href='./%s' class='pure-menu-link'>Download CSV</a></li>\n"
+            "<li class='pure-menu-item'><a href='%s' class='pure-menu-link'>Download CSV</a></li>\n"
 #endif
             "<li class='pure-menu-item' id='led'>&#11044;</li>\n" // LED
             "</ul></div></div>\n"
@@ -132,7 +132,7 @@ namespace web_server {
 #ifdef AMPEL_CSV
             "<script>\n"
             "document.body.style.cursor = 'default';\n"
-            "fetch('./%s',{credentials:'include'})\n"
+            "fetch('%s',{credentials:'include'})\n"
             ".then(response=>response.text())\n"
             ".then(csvText=>csvToTable(csvText))\n"
             ".then(htmlTable=>addLogTableToPage(htmlTable))\n"
@@ -177,7 +177,7 @@ namespace web_server {
     http.on("/", handleWebServerRoot);
     http.on("/command", handleWebServerCommand);
 #ifdef AMPEL_CSV
-    http.on("/" + csv_writer::filename, handleWebServerCSV);
+    http.on(csv_writer::filename, handleWebServerCSV); //NOTE: csv_writer should have been initialized first.
     http.on("/delete_csv", HTTP_POST, handleDeleteCSV);
 #endif
     http.onNotFound(handlePageNotFound);
@@ -212,10 +212,9 @@ namespace web_server {
     char content[2000]; // Update if needed
     // INFO - Header size : 1767 - Body size : 1812 - Script size : 1909
 
-    snprintf_P(content, sizeof(content), header_template, sensor::co2, ampel.sensorId.c_str(),
-        WiFi.localIP().toString().c_str()
+    snprintf_P(content, sizeof(content), header_template, sensor::co2, ampel.sensorId, WiFi.localIP().toString().c_str()
 #ifdef AMPEL_CSV
-        , csv_writer::filename.c_str()
+        , csv_writer::filename
 #endif
         );
 
@@ -225,7 +224,7 @@ namespace web_server {
     http.send_P(200, PSTR("text/html"), content);
 
     // Body
-    snprintf_P(content, sizeof(content), body_template, ampel.sensorId.c_str(), sensor::co2, sensor::temperature,
+    snprintf_P(content, sizeof(content), body_template, ampel.sensorId, sensor::co2, sensor::temperature,
         sensor::humidity, sensor::timestamp, config::measurement_timestep,
 #ifdef AMPEL_CSV
         csv_writer::last_successful_write, config::csv_interval, csv_writer::getAvailableSpace() / 1024,
@@ -237,9 +236,9 @@ namespace web_server {
         lorawan::connected ? "Yes" : "No", LMIC_FREQUENCY_PLAN, lorawan::last_transmission,
         config::lorawan_sending_interval,
 #endif
-        config::temperature_offset, config::auto_calibrate_sensor ? "Yes" : "No", ampel.sensorId.c_str(),
-        ampel.sensorId.c_str(), WiFi.localIP().toString().c_str(), WiFi.localIP().toString().c_str(),
-        get_free_heap_size(), ampel.max_loop_duration, ampel.board, dd, hh, mm, ss);
+        config::temperature_offset, config::auto_calibrate_sensor ? "Yes" : "No", ampel.sensorId, ampel.sensorId,
+        WiFi.localIP().toString().c_str(), WiFi.localIP().toString().c_str(), get_free_heap_size(),
+        ampel.max_loop_duration, ampel.board, dd, hh, mm, ss);
 
     Serial.print(F(" - Body size : "));
     http.sendContent(content);
@@ -248,7 +247,7 @@ namespace web_server {
     // Script
     snprintf_P(content, sizeof(content), script_template
 #ifdef AMPEL_CSV
-        , csv_writer::filename.c_str(), ampel.sensorId.c_str()
+        , csv_writer::filename, ampel.sensorId
 #endif
         );