Need help for type of outdoor temperature variable for Sinope thermostat

I am new on this community and I am not a Smartthings user. Instead of I am using Jeedom. But I need you help because I want to use a Zigbee thermostat from Sinope and it’s supported by Smartthings.
This thermostat is already connected to my installation: I can control temperature and read temperature of the room.
But one of the features of this thermostat is to be able to display outdoor temperature.
I found the driver on this community and it’s available here:

There is this code to send the outdoor temperature to the thermostat:

if (weather) {
		double tempValue
        int outdoorTemp = weather.toInteger()
        if(state?.scale == 'F')
        {//the value sent to the thermostat must be in C
        //the thermostat make the conversion to F
        	outdoorTemp = fahrenheitToCelsius(outdoorTemp).toDouble().round()
		String outdoorTempString
		def isChange = isStateChange(device, name, outdoorTempString)
		def isDisplayed = isChange
		sendEvent( name: "outdoorTemp", value: outdoorTempString, unit: state?.scale, displayed: isDisplayed)
		int outdoorTempValue
		int outdoorTempToSend  
        	cmds += zigbee.writeAttribute(0xFF01, 0x0011, 0x21, 10800)//set the outdoor temperature timeout to 3 hours
            if (outdoorTemp < 0) {
                outdoorTempValue = -outdoorTemp*100 - 65536
                outdoorTempValue = -outdoorTempValue
                outdoorTempToSend = zigbee.convertHexToInt(swapEndianHex(hex(outdoorTempValue)))
                cmds += zigbee.writeAttribute(0xFF01, 0x0010, 0x29, outdoorTempToSend, [mfgCode: 0x119C])
            } else {
                outdoorTempValue = outdoorTemp*100
                int tempa = outdoorTempValue.intdiv(256)
                int tempb = (outdoorTempValue % 256) * 256
                outdoorTempToSend = tempa + tempb
                cmds += zigbee.writeAttribute(0xFF01, 0x0010, 0x29, outdoorTempToSend, [mfgCode: 0x119C])

I tried this line:
cmds += zigbee.writeAttribute(0xFF01, 0x0010, 0x29, outdoorTempToSend, [mfgCode: 0x119C])
with 0 value for “outdoorTempToSend” but it doesn’t work. When I read back the attribut I always see -32768
Probably outdoorTempToSend is not defined with the good type and thermostat doesn’t accept the new value.
Can you tell me what’s the type of this variable?
Thanks for your help

Welcome to the SmartThings Community, @mbdrlp!
So, as I understand, you installed the Zigbee thermostat device in SmartThings using the handler you shared above (this means you copied the DTH and pasted it in your IDE)?
Or directly from the ST app (this means you entered the device catalog and followed the steps displayed)? If so, this is the handler used by the device as this was published by Sinopé

“outdoorTemp” is a custom attribute, which means it is not saved in the ST API, that’s why it is not shown in the mobile app either. To see it on both sides it should be converted to a custom capability and follow other migration steps explained in this post.
I don’t know how Jeedom integrates with SmartThings but not all third-party integrations recognize custom capabilities (especially those that still use the Groovy environment) so, you should verify that first.