Solution:

1) The main difference between the J1708D15 and the HDV100A3 isthat the J1708D15 is just an electrical conversion. The serial datastream on the RS-232 side is exactly the same as on the J1708 side. Bycontrast, the HDV100A3 receives the J1708 data (and J1939), adds messageframing, and then sends the framed messages out the RS-232 port at a differentbaud rate (115.2 kbps default.) 2) In order to see all data on the J1708 bus with the HDV100A3, youneed to send the start receive command. 0x01 0x02 0x01 0x11 0x00 0x15. There are also MID filters available if you only want to see data from aspecific MID.