Can I upgrade to Synchro shifting on a 10s Di2 bike? (Ultegra 6770) I bought a second hand bike with an existing Ultegra DI2 6770 groupset, which is a 10-speed group.  I would like to upgrade the components required in order to have syncro shift on it.

As far as I know syncro shift is not available for 6770 (10-speed Shimano Ultegra Di2). For 6870 (the first 11-speed Ultegra Di2 version), Synchro shift is available if we update the battery to the BT-DN110. (Note: the battery houses the computer system that enables Synchro shift.)

Thus I am wondering what components I need to upgrade from a 6770 groupset?
I just installed a Di2 6770 10spd front and rear derailleur with a BT-DN110 internal battery.

I can confirm that once I update firmware on all the components, eTube does NOT allow me to set up synchro shifting.  

Very disappointed considering the battery has all the hardware necessary to support it.