Hi Michael and all,
I'm also intended to use sync_out or other GPIO to output square wave to
control noise source,
I measured 6V for sync_out and GPIO pin 1.5V.
After digging into ROACH2 schematics(page 25 in
roach2_rev2_schematics.pdf),
I found the differential signal is first converted into single ended by
SN65LVDT2 than
buffered out by THS3091. The THS3091 is given a 12V supply.
After a quick look at THS3091 datasheet, it will output about 12V at
50Ohm load with 15V VS
and 3V with 5V VS, so 6~7V output is reasonable for 12V power supply(a
little lower than expect?).
Can anyone remember why pull the sync_out that high instead of normal
TTL or CMOS level?
If I want to use it to drive a load which expect TTL or CMOS level, how
should I connect them?
Thanks
Yan
------ Original Message ------
From: "Michael D'Cruze" <michael.dcr...@postgrad.manchester.ac.uk>
To: "casper@lists.berkeley.edu" <casper@lists.berkeley.edu>
Sent: 2017-05-12 02:10:26
Subject: [casper] ROACH2 sync_out
Dear all,
I’m planning to use a 0.5Hz square wave, generated from the FPGA and
output via sync_out, to eventually fire our cal diode (via much
cabling). A quick hardware test today shows the sync_out port driving
at circa 7V (!). This is a bit higher than I was expecting. Does this
venture as a whole seem like a particularly bad idea to anyone with
experience using sync_out? Is this output voltage roughly as expected?
Thanks a lot,
Michael
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