Next in this saga: I fashioned a breakout of the usb connector to see if the serial-to-usb adapter was generating signals on the usb lines when the dmm was generating signals on the rs232 lines. This may have been a fool's errand, as it looks like there are constant pulses on the usb with 250 ns rep. rate, and I do not have a differential probe, only two separate probes with a math function on the scope. I think that the usb signals change when the dmm is sending signals, but that is as precise as I can be. The net result is I do not know if the data is reasonably present at the usb end.
Next might be some sort of usb sniffer/logger. Is there such a thing that might provide some insight? On Sat, Dec 16, 2017 at 5:40 PM, Denis Heidtmann <[email protected]> wrote: > Well, just in case...I wired a switched connector. That found no > communication: > denis@denis-ThinkPad-L420:~$ sigrok-cli --driver > mastech-mas345:conn=/dev/ttyUSB0 > --samples 10 > sr: serial: Didn't find a valid packet (read 0 bytes). > No devices found. > > For completeness, here are the interface conditions (in case you can see > anything needing changing): > > denis@denis-ThinkPad-L420:~$ stty -F/dev/ttyUSB0 -a > speed 600 baud; rows 0; columns 0; line = 0; > intr = ^C; quit = ^\; erase = ^?; kill = ^U; eof = ^D; eol = <undef>; > eol2 = <undef>; swtch = <undef>; start = ^Q; stop = ^S; susp = ^Z; rprnt = > ^R; > werase = ^W; lnext = ^V; discard = ^O; min = 1; time = 0; > -parenb -parodd -cmspar cs7 hupcl cstopb cread clocal -crtscts > -ignbrk -brkint -ignpar -parmrk -inpck -istrip -inlcr -igncr icrnl ixon > -ixoff > -iuclc -ixany -imaxbel -iutf8 > opost -olcuc -ocrnl onlcr -onocr -onlret -ofill -ofdel nl0 cr0 tab0 bs0 > vt0 ff0 > isig icanon iexten echo echoe echok -echonl -noflsh -xcase -tostop -echoprt > echoctl echoke -flusho -extproc > > -Denis > > On Sat, Dec 16, 2017 at 4:10 PM, Russell Senior <[email protected] > > wrote: > >> On Sat, Dec 16, 2017 at 3:48 PM, Denis Heidtmann >> <[email protected]> wrote: >> > Yes, Russell, I thought of that. I first need to install the driver for >> > the usb-serial device, recall how I did that on the laptop, and try to >> do >> > it the same way. But I will pursue that when I get access to the >> desktop. >> > >> > Is there a line on the usb that should be bouncing up and down when >> RXD is >> > bouncing? BTW, I notice that the designations rx/tx seem to switch >> > depending on which instrument the terms are referred to. The schematic >> I >> > have clearly shows that the designation RXD applies to the data line >> out of >> > the dmm. TXD is the line sending stuff into the dmm. I am assuming >> that >> > this is OK since I clearly see 10 groups of pulses out of the dmm when I >> > send the command --samples 10. >> >> Yeah, no one ever seems to specify what they mean by TX and RX, or at >> least not in a way I comprehend. I have found the most reliable thing >> is to just try it one way (almost at random), and if that doesn't >> work, reverse and try again. Obviously TX on one side of a UART >> should connect to RX on the other side. Some labelling seems to be to >> "hey, connect TX here!" which suggests that it is RX. Or maybe the >> reverse. Anyway, I have yet to damage anything perceptibly with the >> try-swap-try dance. >> _______________________________________________ >> PLUG mailing list >> [email protected] >> http://lists.pdxlinux.org/mailman/listinfo/plug >> > > _______________________________________________ PLUG mailing list [email protected] http://lists.pdxlinux.org/mailman/listinfo/plug
