Using a cheap yellow display (CYD) to interface to an existing template like a phone

[PeteKnight]

Yes, it’s possible.
Each time one of your interfaces (Blynk or the touchscreen) is updated it needs to update the other interface.
So, if your Blynk app sets a target temperature of 24° then it will trigger the corresponding BLYNK_WRITE(vPin) routine, and you’ll need to update your touchscreen’s target temperature.
The same applies in reverse, with touchscreen input being reflected in the Blynk app via a Blynk.irtualWrite(vPin, value) command.

I do something similar using a Nextion display, but also use Amazon Alexa commands to control the heating/cooling too….

My home automation projects built with MQTT and Node Red

Part 4 – Climate Control In this installment, I’ll talk about my heating and cooling controller. It will be MUCH higher level that the last installment, as the system is quite complex and extremely specific to our situation. Hopefully it might inspire others to look at similar projects of their own. This is still work in progress to a certain extent. The basic climate control functionality works well and I’ve developed and tested some additional features, but in some cases I’ve yet to implemen…

Pete.