[PLUG] com port in guest to usb in host (virtual box)

[Denis Heidtmann]

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 <denis.heidtmann at gmail.com>
wrote:

> Well, just in case...I wired a switched connector.  That found no
> communication:
> denis at 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 at 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 <russell at personaltelco.net
> > wrote:
>
>> On Sat, Dec 16, 2017 at 3:48 PM, Denis Heidtmann
>> <denis.heidtmann at gmail.com> 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.
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>
>