Slowly replacing Strings by C strings

ampel-firmware/co2_sensor.cpp

@@ -22,7 +22,7 @@ namespace sensor {
   uint16_t co2 = 0;
   float temperature = 0;
   float humidity = 0;
-  String timestamp = "";
+  char timestamp[23];
   int16_t stable_measurements = 0;
   uint32_t waiting_color = color::blue;
   bool should_calibrate = false;
@@ -168,7 +168,7 @@ namespace sensor {
 
     if (freshData) {
       // checkTimerDeviation();
-      timestamp = ntp::getLocalTime();
+      ntp::getLocalTime(timestamp);
       co2 = scd30.getCO2();
       temperature = scd30.getTemperature();
       humidity = scd30.getHumidity();

ampel-firmware/co2_sensor.h

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

ampel-firmware/config.public.h

@@ -144,7 +144,7 @@
  */
 
 #  define NTP_SERVER "pool.ntp.org"
-#  define UTC_OFFSET_IN_SECONDS 3600 // [s] 3600 for UTC+1
+#  define UTC_OFFSET_IN_SECONDS 7200 // [s] 3600 for UTC+1, 7200 for UTC+1 and daylight saving time
 
 /**
  * Others

ampel-firmware/csv_writer.cpp

@@ -6,7 +6,7 @@ namespace config {
 }
 namespace csv_writer {
   unsigned long last_written_at = 0;
-  String last_successful_write = "";
+  char last_successful_write[23];
 
 #if defined(ESP8266)
   /**
@@ -145,7 +145,7 @@ namespace csv_writer {
       } else {
         Serial.print(F("CSV - Wrote : "));
         Serial.print(csv_line);
-        last_successful_write = ntp::getLocalTime();
+        ntp::getLocalTime(last_successful_write);
       }
       updateFsInfo();
       delay(50);

ampel-firmware/csv_writer.h

@@ -20,7 +20,7 @@ namespace config {
   extern uint16_t csv_interval; // [s]
 }
 namespace csv_writer {
-  extern String last_successful_write;
+  extern char last_successful_write[23];
   void initialize();
   void logIfTimeHasCome(const String &timeStamp, const int16_t &co2, const float &temperature, const float &humidity);
   int getAvailableSpace();

ampel-firmware/lorawan.cpp

@@ -33,7 +33,7 @@ void os_getDevKey(u1_t *buf) {
 namespace lorawan {
   bool waiting_for_confirmation = false;
   bool connected = false;
-  String last_transmission = "";
+  char last_transmission[23] = "";
 
   void initialize() {
     Serial.println(F("Starting LoRaWAN. Frequency plan : " LMIC_FREQUENCY_PLAN " MHz."));
@@ -65,8 +65,10 @@ namespace lorawan {
   }
 
   void onEvent(ev_t ev) {
+    char current_time[23];
+    ntp::getLocalTime(current_time);
     Serial.print("LoRa - ");
-    Serial.print(ntp::getLocalTime());
+    Serial.print(current_time);
     Serial.print(" - ");
     switch (ev) {
     case EV_JOINING:
@@ -113,7 +115,7 @@ namespace lorawan {
       Serial.println(F("EV_REJOIN_FAILED"));
       break;
     case EV_TXCOMPLETE:
-      last_transmission = ntp::getLocalTime();
+      ntp::getLocalTime(last_transmission);
       Serial.println(F("EV_TXCOMPLETE"));
       break;
     case EV_TXSTART:

ampel-firmware/lorawan.h

@@ -39,7 +39,7 @@ namespace config {
 namespace lorawan {
   extern bool waiting_for_confirmation;
   extern bool connected;
-  extern String last_transmission;
+  extern char last_transmission[];
   void initialize();
   void process();
   void preparePayloadIfTimeHasCome(const int16_t &co2, const float &temp, const float &hum);

ampel-firmware/mqtt.cpp

@@ -25,7 +25,7 @@ namespace mqtt {
 
   String publish_topic;
   const char *json_sensor_format;
-  String last_successful_publish = "";
+  char last_successful_publish[23] = "";
 
   void initialize(String &topic) {
     json_sensor_format = PSTR("{\"time\":\"%s\", \"co2\":%d, \"temp\":%.1f, \"rh\":%.1f}");
@@ -51,7 +51,7 @@ namespace mqtt {
       // Topic is the same as clientID. e.g. 'CO2sensors/ESP3d03da'
       if (mqttClient.publish(publish_topic.c_str(), payload)) {
         Serial.println(F("OK"));
-        last_successful_publish = ntp::getLocalTime();
+        ntp::getLocalTime(last_successful_publish);
       } else {
         Serial.println(F("Failed."));
       }

ampel-firmware/mqtt.h

@@ -11,7 +11,7 @@ namespace config {
   extern uint16_t mqtt_sending_interval; // [s]
 }
 namespace mqtt {
-  extern String last_successful_publish;
+  extern char last_successful_publish[];
   extern bool connected;
   void initialize(String &topic);
   void keepConnection();

ampel-firmware/src/lib/NTPClient-master/NTPClient.cpp

@@ -164,7 +164,7 @@ String NTPClient::getFormattedTime(unsigned long secs) {
 }
 
 // Based on https://github.com/PaulStoffregen/Time/blob/master/Time.cpp
-String NTPClient::getFormattedDate(unsigned long secs) {
+void NTPClient::getFormattedDate(char * formatted_date, unsigned long secs) {
   unsigned long rawTime = (secs ? secs : this->getEpochTime()) / 86400L;  // in days
   unsigned long days = 0, year = 1970;
   uint8_t month;
@@ -187,11 +187,8 @@ String NTPClient::getFormattedDate(unsigned long secs) {
   month++; // jan is month 1
   rawTime++; // first day is day 1
 
-  char formatted_date[23];
-  snprintf(formatted_date, sizeof(formatted_date), "%4lu-%02d-%02lu %s%+03d",
+  snprintf(formatted_date, 23, "%4lu-%02d-%02lu %s%+03d",
       year, month, rawTime, this->getFormattedTime(secs).c_str(), this->_timeOffset / 3600);
-
-  return String(formatted_date);
 }
 
 void NTPClient::end() {

ampel-firmware/src/lib/NTPClient-master/NTPClient.h

@@ -91,7 +91,7 @@ class NTPClient {
     * @return secs argument (or 0 for current date) formatted to ISO 8601
     * like `2004-02-12T15:19:21+00:00`
     */
-    String getFormattedDate(unsigned long secs = 0);
+    void getFormattedDate(char *formatted_date, unsigned long secs = 0);
 
     /**
      * Stops the underlying UDP client

ampel-firmware/util.cpp

@@ -33,8 +33,8 @@ namespace ntp {
     timeClient.update();
   }
 
-  String getLocalTime() {
-    return timeClient.getFormattedDate();
+  void getLocalTime(char *timestamp) {
+    timeClient.getFormattedDate(timestamp);
   }
 }
 

ampel-firmware/util.h

@@ -21,7 +21,7 @@
 namespace ntp {
   void initialize();
   void update();
-  String getLocalTime();
+  void getLocalTime(char* timestamp);
 }
 
 namespace util {

ampel-firmware/web_server.cpp

@@ -226,15 +226,15 @@ namespace web_server {
 
     // Body
     snprintf_P(content, sizeof(content), body_template, SENSOR_ID.c_str(), sensor::co2, sensor::temperature,
-        sensor::humidity, sensor::timestamp.c_str(), config::measurement_timestep,
+        sensor::humidity, sensor::timestamp, config::measurement_timestep,
 #ifdef AMPEL_CSV
-        csv_writer::last_successful_write.c_str(), config::csv_interval, csv_writer::getAvailableSpace() / 1024,
+        csv_writer::last_successful_write, config::csv_interval, csv_writer::getAvailableSpace() / 1024,
 #endif
 #ifdef AMPEL_MQTT
-        mqtt::connected ? "Yes" : "No", mqtt::last_successful_publish.c_str(), config::mqtt_sending_interval,
+        mqtt::connected ? "Yes" : "No", mqtt::last_successful_publish, config::mqtt_sending_interval,
 #endif
 #if defined(AMPEL_LORAWAN) && defined(ESP32)
-        lorawan::connected ? "Yes" : "No", LMIC_FREQUENCY_PLAN, lorawan::last_transmission.c_str(),
+        lorawan::connected ? "Yes" : "No", LMIC_FREQUENCY_PLAN, lorawan::last_transmission,
         config::lorawan_sending_interval,
 #endif
         config::temperature_offset, config::auto_calibrate_sensor ? "Yes" : "No", SENSOR_ID.c_str(), SENSOR_ID.c_str(),