Interfacing microcontroller to BBB


I have a board consisting of PIC micro, ADC, DACs etc running on 5V and need to interface the microcontroller with BBB via UART. For 5V-3.3V interfacing, I plan to use this circuit:
The board gets rectified supply from a transformer. Is it safe to connect the ground terminals of the two devices directly?

You can probably use a voltage divider to get from 5V to 3.3V. And a transistor to get from 3.3V to 5V.

If this is a very low cost device , You can do this , As I understand .
There are lots of jtag cables with parallel port connect to jtag only with 100ohm resister, seems no problem
depend on your max currents