Hi all, I should clarify that having the extra amplitude is actually beneficial to our application, rather than detrimental. I was concerned that the electronics might have been driving too hard, risking future failure, for example.
BW Michael From: dan.werthi...@gmail.com [mailto:dan.werthi...@gmail.com] On Behalf Of Dan Werthimer Sent: 18 May 2017 15:36 To: Zhu, Yan Cc: Michael D'Cruze; casper@lists.berkeley.edu Subject: Re: [casper] ROACH2 sync_out hi zhu yan and michael, to bring the roach2 sync output voltage down to 0 to 5 volts when driving 50 ohms, you could use a connectorized 50 ohm 3 dB attenuator. a 3 dB attenuator should lower the voltage from 0 to 7 volts, down to 0 to 5 volts. best wishes, dan On Thu, May 18, 2017 at 1:31 AM, Zhu, Yan <zhu...@nao.cas.cn<mailto:zhu...@nao.cas.cn>> wrote: 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<mailto:michael.dcr...@postgrad.manchester.ac.uk>> To: "casper@lists.berkeley.edu<mailto:casper@lists.berkeley.edu>" <casper@lists.berkeley.edu<mailto: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 -- You received this message because you are subscribed to the Google Groups "casper@lists.berkeley.edu<mailto:casper@lists.berkeley.edu>" group. To unsubscribe from this group and stop receiving emails from it, send an email to casper+unsubscr...@lists.berkeley.edu<mailto:casper+unsubscr...@lists.berkeley.edu>. To post to this group, send email to casper@lists.berkeley.edu<mailto:casper@lists.berkeley.edu>. -- You received this message because you are subscribed to the Google Groups "casper@lists.berkeley.edu<mailto:casper@lists.berkeley.edu>" group. To unsubscribe from this group and stop receiving emails from it, send an email to casper+unsubscr...@lists.berkeley.edu<mailto:casper+unsubscr...@lists.berkeley.edu>. To post to this group, send email to casper@lists.berkeley.edu<mailto:casper@lists.berkeley.edu>. -- You received this message because you are subscribed to the Google Groups "casper@lists.berkeley.edu<mailto:casper@lists.berkeley.edu>" group. To unsubscribe from this group and stop receiving emails from it, send an email to casper+unsubscr...@lists.berkeley.edu<mailto:casper+unsubscr...@lists.berkeley.edu>. To post to this group, send email to casper@lists.berkeley.edu<mailto:casper@lists.berkeley.edu>. -- You received this message because you are subscribed to the Google Groups "casper@lists.berkeley.edu" group. To unsubscribe from this group and stop receiving emails from it, send an email to casper+unsubscr...@lists.berkeley.edu. To post to this group, send email to casper@lists.berkeley.edu.
