The precise levels are not supposed to make a difference. Below a negative threshold and above a positive threshold should be enough. >From memory, original RS232 was +/- 12V, but any remotely modern PC would use +/- 5V-ish.
https://en.wikipedia.org/wiki/RS-232#Voltage_levels What happens to DTR and RTS when using sigrok? -- Russell On Wed, Dec 13, 2017 at 7:54 PM, Denis Heidtmann <[email protected]> wrote: > To step back a bit I fabricated a little fixture to make it convenient to > test the lines going into the dmm. I found a description of those lines: > 5-pin inline connector. > > pin 1 Gnd > pin 2 TX > pin 3 RTS (must be off) > pin 4 DTR (must be on) > pin 5 RX > > The connections are through optical couplers in the meter, hence the "must > be" conditions. Pin 2 connects to the anode of the led of the input > coupler, pin 3 is connected to the emitter of the output npn through a > resistor, pin 4 connects to the collector of the output npn, and pin 5 > connects directly to the emitter of that npn. > > I ran (what I presume is the vendor's sw) in a VB windows 2000 guest on my > desktop (Lenovo ThinkCentre M92P), which has an RS232 port. The sw > communicates with the dmm fine. I checked the voltages wrt Gnd: > > Pin 2 -10 (the meter I used did not detect the signal - I need to use a > 'scope to see what the signal actually is) > pin 3 -9.5 to -10 > pin 4 +10 to +10.8 on line; -10V off line. > pin 5 data > > When I was examining this with the laptop and the usb-to-serial adapter I > saw voltages no higher than 6.4V. It is possible that explains the lack of > response from the meter, although the sigrok --scan and --show commands did > find the meter. I do not know how the meter could be identified without > valid communication. > > So this is the status. I will check the voltages when connected to the > laptop, and drag out the 'scope to see what I can learn. > > On Mon, Dec 11, 2017 at 12:28 PM, Russell Senior <[email protected]> > wrote: > >> On Mon, Dec 11, 2017 at 11:21 AM, Denis Heidtmann >> <[email protected]> wrote: >> > Is it possible that your command /dev/ttyUSB0 600,cs7,cstopb,-parenb has >> an >> > error? >> >> Not only possible, but likely. >> >> > I executed stty 600 then stty -a : >> > denis@denis-ThinkPad-L420:~$ stty -a >> > speed 600 baud; rows 24; columns 80; 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 cs8 -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 >> > >> > Then I tried stty cs7 and got: >> > denis@denis-ThinkPad-L420:~$ stty cs7 >> > stty: 'standard input': Invalid argument >> > >> > Yet the man page lists csN. >> > >> > Clearly I do not know what I am doing. >> >> You probably need to tell it which tty you want to talk to, otherwise >> it will try to set your current terminal, afaik. >> >> The device-busy thing may be due to a screen session still running. >> Try unplugging/replugging your cable from the USB port. >> _______________________________________________ >> PLUG mailing list >> [email protected] >> http://lists.pdxlinux.org/mailman/listinfo/plug >> > _______________________________________________ > PLUG mailing list > [email protected] > http://lists.pdxlinux.org/mailman/listinfo/plug _______________________________________________ PLUG mailing list [email protected] http://lists.pdxlinux.org/mailman/listinfo/plug
