I have my heatpump mysensor working, and hooked up to Openhab.

Arduino code here:

#include <MySensor.h>
#include <SPI.h>
#include <Arduino.h>

#include <PanasonicCKPHeatpumpIR.h>
#include <PanasonicHeatpumpIR.h>

#define POWER_ID 0
#define MODE_ID 1
#define FAN_ID 2
#define TEMP_ID 3
#define VDIR_ID 4
#define HDIR_ID 5


MySensor gw;
MyMessage powerMsg(POWER_ID, V_STATUS); 
MyMessage modeMsg(MODE_ID, V_HVAC_FLOW_STATE);
MyMessage fanMsg(FAN_ID, V_PERCENTAGE);
MyMessage tempMsg(TEMP_ID, V_TEMP);
MyMessage vdirMsg(VDIR_ID, V_VAR1); 
MyMessage hdirMsg(HDIR_ID, V_VAR2); 

IRSenderPWM irSender(3);       // IR led on Arduino digital pin 3, using Arduino PWM

HeatpumpIR *heatpumpIR = new PanasonicNKEHeatpumpIR();

//Some global variables to hold the states
int POWER_STATE;
int TEMP_STATE;
int FAN_STATE;
int MODE_STATE;

void setup()  
{  
  gw.begin(incomingMessage, AUTO, false);

  // Send the sketch version information to the gateway and Controller
  gw.sendSketchInfo("Heatpump", "1.0");

  // Register all sensors to gw (they will be created as child devices)
  gw.present(POWER_ID, S_BINARY);
  gw.present(MODE_ID, S_HVAC);
  gw.present(FAN_ID, S_HVAC);
  gw.present(TEMP_ID, S_HVAC);
  gw.present(VDIR_ID, S_CUSTOM);
  gw.present(HDIR_ID, S_CUSTOM);
     
  // Load our values on start
  POWER_STATE = gw.loadState(POWER_ID);
  TEMP_STATE = gw.loadState(TEMP_ID);
  FAN_STATE = gw.loadState(FAN_ID);
  MODE_STATE = gw.loadState(MODE_ID);
  
  sendHeatpumpCommand();
}

void loop() {
  gw.process();
} 

void handlePowerMessage(bool newState) {
  if (newState) {
    POWER_STATE = POWER_ON;
  }
  else {
    POWER_STATE = POWER_OFF;
  }
  gw.saveState(POWER_ID, newState);
}

void handleModeMessge(int newMode) {
  switch(newMode) {    
    case 0:
      MODE_STATE = MODE_HEAT; break;
    case 1:
      MODE_STATE = MODE_COOL; break;
    case 2:
      MODE_STATE = MODE_AUTO; break;
    case 3:
      MODE_STATE = MODE_FAN; break;
     case 4:
      MODE_STATE = MODE_DRY; break;
  }
  MODE_STATE = newMode;
  gw.saveState(MODE_ID, newMode);
}

void handleFanMessage(int newFan) {
  if (newFan > 5) newFan=5;
  switch(newFan) {
    case 0:
      FAN_STATE = FAN_AUTO; break;
    case 1:
      FAN_STATE = FAN_1; break;
    case 2:
      FAN_STATE = FAN_2; break;
    case 3:
      FAN_STATE = FAN_3; break;
    case 4:
      FAN_STATE = FAN_4; break;
    case 5:
      FAN_STATE = FAN_5; break;
    default:
      FAN_STATE = FAN_AUTO; break;
  }
  FAN_STATE = newFan;
  gw.saveState(FAN_ID, newFan);
}

void handleTempMessage(int newTemp) {
  TEMP_STATE = newTemp;
  gw.saveState(TEMP_ID, newTemp);
}

void sendHeatpumpCommand() {
  Serial.println("Power = " + (String)POWER_STATE);
  Serial.println("Mode = " + (String)MODE_STATE);
  Serial.println("Fan = " + (String)FAN_STATE);
  Serial.println("Temp = " + (String)TEMP_STATE);
  heatpumpIR->send(irSender, POWER_STATE, MODE_STATE, FAN_STATE, TEMP_STATE, VDIR_AUTO, HDIR_AUTO);
}
void incomingMessage(const MyMessage &message) {
  // We only expect one type of message from controller. But we better check anyway.
  if (message.isAck()) {
     Serial.println("This is an ack from gateway");
  }
   Serial.print("Incoming change for sensor:");
   Serial.print(message.sensor);
   Serial.print(", New status: ");
   Serial.println(message.getBool());

   switch(message.sensor) {
    case POWER_ID: {
      bool newState = message.getBool();
      handlePowerMessage(newState);
      break;
    }
    case MODE_ID: {
      int newMode = message.getInt();
      handleModeMessge(newMode);
      break;
    }
    case FAN_ID: {
      int newFan = message.getInt();
      handleFanMessage(newFan);
      break;
    }
    case TEMP_ID: {
      int newTemp = message.getInt();
      handleTempMessage(newTemp);
      break;
    }
   }
  sendHeatpumpCommand();
}

Openhab items

Switch	Power_HeatPump	"Heatpump on/off" <aircon>
Number	Mode_HeatPump	"Heatpump mode"
Number	Fan_HeatPump	"Heatpump fan" <airing>
Number	Temp_HeatPump	"Heatpump temperature [%d C]"	<temperature>
String	VDir_HeatPump	"vertical"
String	HDir_HeatPump	"horizontal"

Openhab sitemap

sitemap heatpump label="Heatpump" {
  Frame {
    Switch item=Power_HeatPump
    Selection item=Mode_HeatPump mappings=[0="heat", 1="cool", 2="auto", 3="fan", 4="dry"]
    Selection item=Fan_HeatPump mappings=[0="auto", 1="Level 1", 2="Level 2", 3="Level 3", 4="Level 4", 5="Level 5"]
    Setpoint item=Temp_HeatPump minValue=10 maxValue=30 step=1
    Text item=VDir_HeatPump
    Text item=HDir_HeatPump
  }
}

Openhab rules

val org.eclipse.xtext.xbase.lib.Functions$Function4 numberOperation = [
    org.openhab.core.library.items.NumberItem numberItem, 
    org.openhab.core.library.items.StringItem arduinoItem, 
    String arduinoDevMap,
    Integer subType|
    logInfo("number", "Sending number message to mysensors node")
    var Integer state = numberItem.state
    logInfo("mysensors", "Function: numberOperation >> "+arduinoDevMap + "1;1;" + subType + ";" + state )
    arduinoItem.sendCommand(arduinoDevMap + "1;0;" + subType + ";" + state + "\n")
]

//switch function
val org.eclipse.xtext.xbase.lib.Functions$Function4 switchOperation = [
    org.openhab.core.library.items.SwitchItem relayItem, 
    org.openhab.core.library.items.StringItem arduinoItem, 
    String arduinoDevMap,
    Integer subType|
    logInfo("switch", "Sending switch message to mysensors node")
    
    var Integer state = 0
    if (relayItem.state == OFF) {
        state = 0 
    }
    else {
        state = 1
    }
    logInfo("mysensors", "Function: switchOperation >> "+arduinoDevMap + "1;1;" + subType + ";" + state )
    arduinoItem.sendCommand(arduinoDevMap + "1;0;" + subType + ";" + state + "\n")
]




rule "Heatpump on"
when
    Item Power_HeatPump received command
then
    switchOperation.apply(Power_HeatPump, MySensors_Gateway, sensorToItemsMap.get("Power_HeatPump"),  V_STATUS)         
end 

rule "Heatpump mode"
when
    Item Mode_HeatPump received update
then
    numberOperation.apply(Mode_HeatPump, MySensors_Gateway, sensorToItemsMap.get("Mode_HeatPump"),  V_VAR1)         
end 


rule "Heatpump temp"
when
    Item Temp_HeatPump received command
then
    numberOperation.apply(Temp_HeatPump, MySensors_Gateway, sensorToItemsMap.get("Temp_HeatPump"),  V_TEMP)         
end 

rule "heatpump fan"
when
    Item Fan_HeatPump received command
then
    numberOperation.apply(Fan_HeatPump, MySensors_Gateway, sensorToItemsMap.get("Fan_HeatPump"),  V_PERCENTAGE)         
end