Simply set your global variable v to the value of the tag speed when it is returned in GotValue …then call drawGauge.
Do not call drawGauge in your initialise block because the value in v will be the default (10), not the firebase value.
Global v is empty and math blocks “hates” empty strings. If tag not there set value to 1 for example instead of empty string. Make sure you are using correct tag and that you are getting value from firebase
i’ve tried to fill that with 0 and string " " (empty), but i still got an error
I’ll try it again, thank you so much! 