80
FPGA circuit to the line driver circuits using 15-pin and 25-pin IDSD cables, with
0.1” pin-to-pin separation, and TSW connectors. The SHF cable connectors and
FFSD cables for connection between the line driver circuits and the SLM board are
smaller in size, with only 0.05” pin-to-pin separation.
Caution: The FFSD cable headers break easily when disconnecting from the SHF
connectors, once they are soldered onto the PCB. Always use a small hat-head screw
driver and unplug the cables by piling the screw driver in the gap between the cable
header and the connector. FTSH or FTS connectors are preferred over SHF in future
designs.
Suggestion: FFSD cable length should be at least 40” for more flexible movement of
the SLM board during experiment.
B.7 Synchronization with Т-ray system
Every time the control system changes the pattern on the SLM, it needs to trigger
the Т-ray system to acquire a new waveform. This synchronization between the SLM
and the waveform acquisition requires the time sequencing option implemented in the
picometrix T-ray 4000 system. First, connect the trigger output of the FPGA circuit
to the SYNC IN connector at the back of the T-ray 4000 control box using a BNC
cable. The trigger signal needs to be a 5V TTL level pulse. Our system has a voltage
amplifier circuit similar to the one in Figure B.5, which converts the trigger output of
the FPGA circuit from 2.5V to 5V. Also, the system cannot detect any trigger signal
with pulse width smaller than 250 μs. Then, under the Tools Menu of the T-ray
4000 software, choose Time Sequencing. Always choose ,,extrn sync” in the pulldown