diff --git a/DCCRMT.h b/DCCRMT.h
index 33257a0..3a20027 100644
--- a/DCCRMT.h
+++ b/DCCRMT.h
@@ -44,6 +44,12 @@ class RMTChannel {
       return true;
     return dataReady;
   };
+  inline void waitForDataCopy() {
+    while(1) { // do nothing and wait for interrupt clearing dataReady to happen
+      if (dataReady == false)
+	break;
+    }
+  };
   inline uint32_t packetCount() { return packetCounter; };
   
  private:
diff --git a/DCCWaveform.cpp b/DCCWaveform.cpp
index 3d77e9e..eb25144 100644
--- a/DCCWaveform.cpp
+++ b/DCCWaveform.cpp
@@ -278,7 +278,11 @@ void DCCWaveform::begin() {
 
 void DCCWaveform::schedulePacket(const byte buffer[], byte byteCount, byte repeats) {
   if (byteCount > MAX_PACKET_SIZE) return; // allow for chksum
-  
+  RMTChannel *rmtchannel = (isMainTrack ? rmtMainChannel : rmtProgChannel);
+  if (rmtchannel == NULL)
+    return; // no idea to prepare packet if we can not send it anyway
+
+  rmtchannel->waitForDataCopy(); // blocking wait so we can write into buffer
   byte checksum = 0;
   for (byte b = 0; b < byteCount; b++) {
     checksum ^= buffer[b];
@@ -296,13 +300,7 @@ void DCCWaveform::schedulePacket(const byte buffer[], byte byteCount, byte repea
   {
     int ret = 0;
     do {
-      if(isMainTrack) {
-	if (rmtMainChannel != NULL)
-	  ret = rmtMainChannel->RMTfillData(pendingPacket, pendingLength, pendingRepeats);
-      } else {
-	if (rmtProgChannel != NULL)
-	  ret = rmtProgChannel->RMTfillData(pendingPacket, pendingLength, pendingRepeats);
-      }
+      ret = rmtchannel->RMTfillData(pendingPacket, pendingLength, pendingRepeats);
     } while(ret > 0);
   }
 }