MariaDB MySQL querey


I am trying to get Grafrana to graph my SQL data which is very simple but I am struggling with the following error

This is the Query
UNIX_TIMESTAMP(time_stamp) as time_sec,
calls as value,
FROM active_calls
WHERE $__timeFilter(time_stamp)
ORDER BY <time_stamp> ASC

this is the error

Error 1064: You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near ‘FROM active_calls
WHERE time_stamp >= FROM_UNIXTIME(1500850800) AND time_stamp <’ at line 4

My MySQL data structure is very simple, see attached from active_calls table

Any ideas how to get this working?

You can < and > signs in your query replace them with the right column name