The signaling on a PC RS232 line is +nV and -nV, where n is somewhere between 5 and 12, inclusive. So, I think -6V would be a zero and a +6V would be a one.
I think you can use GNU screen here, with the following options (serial parameters are from the manpage from stty(1): screen /dev/ttyUSB0 600,cs7,cstopb,-parenb Not sure this is doing the suggested thing for RTS and DTR. On Sun, Dec 10, 2017 at 8:41 PM, Denis Heidtmann <[email protected]> wrote: > I notice that 12 V is mentioned. I measure ~6 V from ground to every pin > except RxD, which is zero. (All DC; when not sending data.) Could this be > the issue? > > On Sun, Dec 10, 2017 at 6:28 PM, Denis Heidtmann <[email protected]> > wrote: > >> Here is the protocol description I recall finding: >> >> MAS345: >> >> data format: 7n2 at 600 baud (7 bits, no parity, 2 stop bits). >> Control lines: >> DTR and RTS lines are used to power the TX line: RTS is clear >> for -12 supply; DTR is set for +12 supply. Data transmission is >> solicited sending whatever character to the RX line. >> Data string format: >> MAS-345 sends a 14 bytes string with: >> <mode>< ><sign><value>< ><units><return> >> <mode>: two bytes with the oerating mode: DC, AC, OH, CA, TE ... >> <sign>: one byte with - or space >> <value>: five bytes with four digits and one decimal dot. >> <units>: four bytes with the units: mV, A, kOhm, nF ... >> <return>: '\r' >> One space is inserted between <mode> and <sign>, one between >> <value> and <units>. >> The data string (without the '\r') is sent to the output device. >> >> On Sun, Dec 10, 2017 at 6:11 PM, Denis Heidtmann < >> [email protected]> wrote: >> >>> The protocol I recall seeing documented was 7n2, 600 baud. I must >>> confess I do not know how to talk directly over serial. I tried Google, >>> but there were too many options and opinions. What do you recommend for >>> this simple task? >>> >>> On Sun, Dec 10, 2017 at 3:01 PM, Russell Senior < >>> [email protected]> wrote: >>> >>>> Try talking to the DMM directly over serial. The protocol description >>>> says: >>>> >>>> Various multimeters from Metex (and rebadged ones) use this common >>>> 14-byte packet based ASCII protocol. The actual multimeter ICs in the >>>> devices have different names (e.g. "MASTECH M343-01" or "Metex >>>> KS57C2016") but they all use the same common protocol format. >>>> >>>> The serial port settings can vary from device to device, e.g. >>>> 600/1200 baud, 7n2, RTS low, DTR high. >>>> >>>> If you get the serial parameters right, you ought to be able to talk >>>> directly at it (e.g. send a D and get a string of bytes). Maybe you >>>> can snoop the serial with an oscilloscope while running the vendor >>>> interface software and figure out the baud,et al. >>>> >>>> On Sun, Dec 10, 2017 at 2:08 PM, Denis Heidtmann >>>> <[email protected]> wrote: >>>> > Thanks for the -help. I got part of that -help when I entered an >>>> incorrect >>>> > option, but somehow missed the -- entries at the end. Here is what I >>>> get: >>>> > >>>> > denis@denis-ThinkPad-L420:~$ sigrok-cli --driver >>>> > mastech-mas345:conn=/dev/ttyUSB0 --scan >>>> > The following devices were found: >>>> > mastech-mas345 - MASTECH MAS345 with 1 channel: P1 >>>> > >>>> > denis@denis-ThinkPad-L420:~$ sigrok-cli --driver >>>> > mastech-mas345:conn=/dev/ttyUSB0 --show >>>> > mastech-mas345 - MASTECH MAS345 with 1 channel: P1 >>>> > Supported driver options: >>>> > conn >>>> > serialcomm >>>> > Supported configuration options: >>>> > denis@denis-ThinkPad-L420:~$ >>>> > >>>> > Additionally I tried: >>>> > denis@denis-ThinkPad-L420:~$ sigrok-cli --driver >>>> > mastech-mas345:conn=/dev/ttyUSB0 --loglevel 5 >>>> > sr: libsigrok loglevel set to 5. >>>> > sr: backend: Sanity-checking all drivers. >>>> > sr: backend: Sanity-checking all input modules. >>>> > sr: backend: Sanity-checking all output modules. >>>> > srd: libsigrokdecode loglevel set to 5. >>>> > Usage: >>>> > sigrok-cli [OPTION...] >>>> > snip... >>>> > >>>> > I also tried the --output-file but nothing. I found that I could not >>>> enter >>>> > more than one option at a time---I tried --scan and --show but only the >>>> > first one was responded to. >>>> > >>>> > BTW, recall that this instrument worked as expected using the vendor's >>>> > windows sw on the desktop, where I have a serial port. So I do not >>>> suspect >>>> > the hardware outside the laptop. >>>> > >>>> > These results are encouraging, but no cigar. >>>> > >>>> > -Denis >>>> > _______________________________________________ >>>> > 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 _______________________________________________ PLUG mailing list [email protected] http://lists.pdxlinux.org/mailman/listinfo/plug
