diff --git a/src/LoraEncoder.cpp b/src/LoraEncoder.cpp
index f8f4909..0f945d8 100644
--- a/src/LoraEncoder.cpp
+++ b/src/LoraEncoder.cpp
@@ -24,24 +24,58 @@
   SOFTWARE.
 */
 
+#define O_TEMP 0x01 // Temperature is a one-byte code
+#define O_HUMI 0x02 // Humidity is a one-byte code
+#define O_AIRP 0x03 // Air pressure is a one-byte code
+#define O_GPS 0x04 // Short version: ONLY 3 bytes LAT and 3 bytes LONG
+#define O_GPSL 0x05 // Long GPS
+#define O_PIR 0x06 // Movement, 1 bit (=1 byte)
+#define O_AQ 0x07 // Airquality
+#define O_RTC 0x08 // Real Time Clock
+#define O_COMPASS 0x09 // Compass
+#define O_MB 0x0A // Multi Sensors 433
+#define O_MOIST 0x0B // Moisture is one-byte
+#define O_LUMI 0x0C // Luminescense u16
+#define O_DIST 0x0D // Distance is 2-byte
+#define O_GAS 0x0E // GAS
+
+/* 0x10 to 0x1F are free */
+
+#define O_BATT 0x20 // Internal Battery
+#define O_ADC0 0x21 // AD converter on pin 0
+#define O_ADC1 0x22
+
+// Reserved for LoRa messages (especially downstream)
+#define O_STAT 0x30 // Ask for status message from node
+#define O_SF 0x31 // Spreading factor change OFF=0, values 7-12
+#define O_TIM 0x32 // Timing of the wait cyclus (20 to 7200 seconds)
+#define O_1CH 0x33 // Single channel ON=1, OFF==0
+#define O_LOC 0x34 // Ask for the location. Responds with GPS location (if available)
+
 #if ARDUINO >= 100
     #include "Arduino.h"
 #endif
 #include "LoraEncoder.h"
 
-LoraEncoder::LoraEncoder(byte *buffer) {
+LoraEncoder::LoraEncoder(byte *buffer, bool opcodes) {
   _buffer = buffer;
+  _opcodes = opcodes;
+}
+
+void LoraEncoder::_addOpcode(byte *buf, uint8_t byteMode, uint8_t byteSize) {
+    buf[0] = byteMode << 2 | byteSize;
 }
 
 void LoraEncoder::_intToBytes(byte *buf, int32_t i, uint8_t byteSize) {
-    for(uint8_t x = 0; x < byteSize; x++) {
+    for(uint8_t x = _opcodes; x < (byteSize + _opcodes); x++) {
         buf[x] = (byte) (i >> (x*8));
     }
 }
 
 void LoraEncoder::writeUnixtime(uint32_t unixtime) {
+    if (_opcodes) { _addOpcode(_buffer, O_RTC, 4); }
     _intToBytes(_buffer, unixtime, 4);
-    _buffer += 4;
+    _buffer += 4 + _opcodes;
 }
 
 void LoraEncoder::writeLatLng(double latitude, double longitude) {
@@ -64,9 +98,10 @@ void LoraEncoder::writeUint8(uint8_t i) {
 }
 
 void LoraEncoder::writeHumidity(float humidity) {
+    if (_opcodes) { _addOpcode(_buffer, O_HUMI, 2); }
     int16_t h = (int16_t) (humidity * 100);
     _intToBytes(_buffer, h, 2);
-    _buffer += 2;
+    _buffer += 2 + _opcodes;
 }
 
 /**
diff --git a/src/LoraEncoder.h b/src/LoraEncoder.h
index 2e2d23a..b64cdb4 100644
--- a/src/LoraEncoder.h
+++ b/src/LoraEncoder.h
@@ -36,7 +36,7 @@
 
 class LoraEncoder {
     public:
-        LoraEncoder(byte *buffer);
+        LoraEncoder(byte *buffer, bool opcodes = 0);
         void writeUnixtime(uint32_t unixtime);
         void writeLatLng(double latitude, double longitude);
         void writeUint16(uint16_t i);
@@ -47,6 +47,8 @@ class LoraEncoder {
     private:
         byte* _buffer;
         void _intToBytes(byte *buf, int32_t i, uint8_t byteSize);
+        void _addOpcode(byte *buf, uint8_t byteMode, uint8_t byteSize);
+        bool _opcodes;
 };
 
 #endif
diff --git a/src/LoraMessage.cpp b/src/LoraMessage.cpp
index 31cd9ff..0456721 100644
--- a/src/LoraMessage.cpp
+++ b/src/LoraMessage.cpp
@@ -5,9 +5,10 @@
 #include "LoraMessage.h"
 #include "LoraEncoder.h"
 
-LoraMessage::LoraMessage() {
+LoraMessage::LoraMessage(bool opcodes) {
     _currentSize = 0;
     _buffer = (byte*) malloc(_currentSize);
+    _opcodes = opcodes;
 }
 
 LoraMessage::~LoraMessage() {
@@ -15,6 +16,7 @@ LoraMessage::~LoraMessage() {
 }
 
 LoraEncoder LoraMessage::_reallocBuffer(int delta) {
+    delta += _opcodes;
     void* temp = realloc(_buffer, (_currentSize + delta) * sizeof(byte));
     if (temp == NULL) {
         free(_buffer);
@@ -23,7 +25,7 @@ LoraEncoder LoraMessage::_reallocBuffer(int delta) {
     } else {
         _buffer = (byte*) temp;
     }
-    LoraEncoder encoder(_buffer + _currentSize);
+    LoraEncoder encoder(_buffer + _currentSize, _opcodes);
     _currentSize += delta;
     return encoder;
 }
diff --git a/src/LoraMessage.h b/src/LoraMessage.h
index b3deb42..30f409d 100644
--- a/src/LoraMessage.h
+++ b/src/LoraMessage.h
@@ -12,7 +12,7 @@
 
 class LoraMessage {
     public:
-        LoraMessage();
+        LoraMessage(bool opcodes = 0);
         ~LoraMessage();
         LoraMessage& addUnixtime(uint32_t unixtime);
         LoraMessage& addLatLng(double latitude, double longitude);
@@ -27,6 +27,7 @@ class LoraMessage {
         LoraEncoder _reallocBuffer(int delta);
         byte* _buffer;
         int _currentSize;
+        bool _opcodes;
 };
 
 #endif