Unfortunately TimesTen is only ODBC 2.0 compliant which means that you will not be able to connect to TimesTEn from your Tableau. Simply it won't work.
We have been working on this With Oracle and Company called Progress software to use their custom built drivers to connect to oracle TimesTen. We have had some success up to now. In general no custom SQL seems to work with TimesTen or Oracle itself through ODBC drivers (supplied by Oracle). In all our cases Tableau, drivers and DB we are talking 64-bit.
It seems that most of the limitations are coming from Tableau itself as well. Bear in mind that TimesTen will not have ODBC 3.0 drivers for a good while.
Bear in mind that Tableau requires an ODBC 3.0 compliant driver. Progress software Sequelink ODBC driver is 3.0 compliant. Howerver, the underlying driver is the limiting factor here as TimesTen ODBC driver is an ODBC 2.0 driver. Sequelink Socket server will map the ODBC 3.0 calls to ODBC 2.0. Unfortunately it cannot add ODBC 3.0 functionality.