diff --git a/include/MessageOutput.h b/include/MessageOutput.h
index 3a30bff..9c28de2 100644
--- a/include/MessageOutput.h
+++ b/include/MessageOutput.h
@@ -21,7 +21,7 @@ private:
 
     Task _loopTask;
 
-    AsyncWebSocket* _ws = NULL;
+    AsyncWebSocket* _ws = nullptr;
     char _buffer[BUFFER_SIZE];
     uint16_t _buff_pos = 0;
     uint32_t _lastSend = 0;
diff --git a/include/NetworkSettings.h b/include/NetworkSettings.h
index 6bd99ec..ef80566 100644
--- a/include/NetworkSettings.h
+++ b/include/NetworkSettings.h
@@ -30,7 +30,7 @@ typedef struct NetworkEventCbList {
     network_event event;
 
     NetworkEventCbList()
-        : cb(NULL)
+        : cb(nullptr)
         , event(network_event::NETWORK_UNKNOWN)
     {
     }
diff --git a/include/WebApi_prometheus.h b/include/WebApi_prometheus.h
index b03f817..e002798 100644
--- a/include/WebApi_prometheus.h
+++ b/include/WebApi_prometheus.h
@@ -13,7 +13,7 @@ public:
 private:
     void onPrometheusMetricsGet(AsyncWebServerRequest* request);
 
-    void addField(AsyncResponseStream* stream, String& serial, uint8_t idx, std::shared_ptr<InverterAbstract> inv, ChannelType_t type, ChannelNum_t channel, FieldId_t fieldId, const char* metricName, const char* channelName = NULL);
+    void addField(AsyncResponseStream* stream, String& serial, uint8_t idx, std::shared_ptr<InverterAbstract> inv, ChannelType_t type, ChannelNum_t channel, FieldId_t fieldId, const char* metricName, const char* channelName = nullptr);
 
     void addPanelInfo(AsyncResponseStream* stream, String& serial, uint8_t idx, std::shared_ptr<InverterAbstract> inv, ChannelType_t type, ChannelNum_t channel);
 
diff --git a/lib/Hoymiles/src/parser/StatisticsParser.cpp b/lib/Hoymiles/src/parser/StatisticsParser.cpp
index b436f43..da5078c 100644
--- a/lib/Hoymiles/src/parser/StatisticsParser.cpp
+++ b/lib/Hoymiles/src/parser/StatisticsParser.cpp
@@ -128,7 +128,7 @@ const byteAssign_t* StatisticsParser::getAssignmentByChannelField(ChannelType_t
             return &_byteAssignment[i];
         }
     }
-    return NULL;
+    return nullptr;
 }
 
 fieldSettings_t* StatisticsParser::getSettingByChannelField(ChannelType_t type, ChannelNum_t channel, FieldId_t fieldId)
@@ -138,13 +138,13 @@ fieldSettings_t* StatisticsParser::getSettingByChannelField(ChannelType_t type,
             return &i;
         }
     }
-    return NULL;
+    return nullptr;
 }
 
 float StatisticsParser::getChannelFieldValue(ChannelType_t type, ChannelNum_t channel, FieldId_t fieldId)
 {
     const byteAssign_t* pos = getAssignmentByChannelField(type, channel, fieldId);
-    if (pos == NULL) {
+    if (pos == nullptr) {
         return 0;
     }
 
@@ -174,7 +174,7 @@ float StatisticsParser::getChannelFieldValue(ChannelType_t type, ChannelNum_t ch
         result /= static_cast<float>(div);
 
         const fieldSettings_t* setting = getSettingByChannelField(type, channel, fieldId);
-        if (setting != NULL && _statisticLength > 0) {
+        if (setting != nullptr && _statisticLength > 0) {
             result += setting->offset;
         }
         return result;
@@ -189,7 +189,7 @@ float StatisticsParser::getChannelFieldValue(ChannelType_t type, ChannelNum_t ch
 bool StatisticsParser::setChannelFieldValue(ChannelType_t type, ChannelNum_t channel, FieldId_t fieldId, float value)
 {
     const byteAssign_t* pos = getAssignmentByChannelField(type, channel, fieldId);
-    if (pos == NULL) {
+    if (pos == nullptr) {
         return false;
     }
 
@@ -202,7 +202,7 @@ bool StatisticsParser::setChannelFieldValue(ChannelType_t type, ChannelNum_t cha
     }
 
     const fieldSettings_t* setting = getSettingByChannelField(type, channel, fieldId);
-    if (setting != NULL) {
+    if (setting != nullptr) {
         value -= setting->offset;
     }
     value *= static_cast<float>(div);
@@ -236,7 +236,7 @@ String StatisticsParser::getChannelFieldValueString(ChannelType_t type, ChannelN
 bool StatisticsParser::hasChannelFieldValue(ChannelType_t type, ChannelNum_t channel, FieldId_t fieldId)
 {
     const byteAssign_t* pos = getAssignmentByChannelField(type, channel, fieldId);
-    return pos != NULL;
+    return pos != nullptr;
 }
 
 const char* StatisticsParser::getChannelFieldUnit(ChannelType_t type, ChannelNum_t channel, FieldId_t fieldId)
@@ -260,7 +260,7 @@ uint8_t StatisticsParser::getChannelFieldDigits(ChannelType_t type, ChannelNum_t
 float StatisticsParser::getChannelFieldOffset(ChannelType_t type, ChannelNum_t channel, FieldId_t fieldId)
 {
     const fieldSettings_t* setting = getSettingByChannelField(type, channel, fieldId);
-    if (setting != NULL) {
+    if (setting != nullptr) {
         return setting->offset;
     }
     return 0;
@@ -269,7 +269,7 @@ float StatisticsParser::getChannelFieldOffset(ChannelType_t type, ChannelNum_t c
 void StatisticsParser::setChannelFieldOffset(ChannelType_t type, ChannelNum_t channel, FieldId_t fieldId, float offset)
 {
     fieldSettings_t* setting = getSettingByChannelField(type, channel, fieldId);
-    if (setting != NULL) {
+    if (setting != nullptr) {
         setting->offset = offset;
     } else {
         _fieldSettings.push_back({ type, channel, fieldId, offset });
@@ -444,7 +444,7 @@ static float calcEffiencyCh0(StatisticsParser* iv, uint8_t arg0)
 // arg0 = channel
 static float calcIrradiation(StatisticsParser* iv, uint8_t arg0)
 {
-    if (NULL != iv) {
+    if (nullptr != iv) {
         if (iv->getStringMaxPower(arg0) > 0)
             return iv->getChannelFieldValue(TYPE_DC, static_cast<ChannelNum_t>(arg0), FLD_PDC) / iv->getStringMaxPower(arg0) * 100.0f;
     }
diff --git a/src/Configuration.cpp b/src/Configuration.cpp
index a77868d..27ad0b6 100644
--- a/src/Configuration.cpp
+++ b/src/Configuration.cpp
@@ -357,7 +357,7 @@ INVERTER_CONFIG_T* ConfigurationClass::getFreeInverterSlot()
         }
     }
 
-    return NULL;
+    return nullptr;
 }
 
 INVERTER_CONFIG_T* ConfigurationClass::getInverterConfig(uint64_t serial)
@@ -368,7 +368,7 @@ INVERTER_CONFIG_T* ConfigurationClass::getInverterConfig(uint64_t serial)
         }
     }
 
-    return NULL;
+    return nullptr;
 }
 
 ConfigurationClass Configuration;
\ No newline at end of file
diff --git a/src/WebApi_prometheus.cpp b/src/WebApi_prometheus.cpp
index 6178f53..afa0eff 100644
--- a/src/WebApi_prometheus.cpp
+++ b/src/WebApi_prometheus.cpp
@@ -102,7 +102,7 @@ void WebApiPrometheusClass::onPrometheusMetricsGet(AsyncWebServerRequest* reques
 void WebApiPrometheusClass::addField(AsyncResponseStream* stream, String& serial, uint8_t idx, std::shared_ptr<InverterAbstract> inv, ChannelType_t type, ChannelNum_t channel, FieldId_t fieldId, const char* metricName, const char* channelName)
 {
     if (inv->Statistics()->hasChannelFieldValue(type, channel, fieldId)) {
-        const char* chanName = (channelName == NULL) ? inv->Statistics()->getChannelFieldName(type, channel, fieldId) : channelName;
+        const char* chanName = (channelName == nullptr) ? inv->Statistics()->getChannelFieldName(type, channel, fieldId) : channelName;
         if (idx == 0 && type == TYPE_AC && channel == 0) {
             stream->printf("# HELP opendtu_%s in %s\n", chanName, inv->Statistics()->getChannelFieldUnit(type, channel, fieldId));
             stream->printf("# TYPE opendtu_%s %s\n", chanName, metricName);