My goal is to be able to get data from the dmm using my laptop, which has only USB. I have an RS-232--USB adapter. Eventually I want to make the choices more friendly.
Later today I will study the details of your observations. The protocol I have seen described elsewhere says the host needs to send a single byte (H?) to get the dmm to send one reading. I had to change two time values and remove the setTimeout line to get it to work. At present it locks the meter for some time. I expect that is because the host is sending bytes too fast, causing the meter to try to respond before it is ready, a difficulty I saw referenced in another description of how to deal with this meter. Thanks for looking at the code. -Denis On Sun, Jan 7, 2018 at 12:35 PM, Galen Seitz <gal...@seitzassoc.com> wrote: > On 01/07/18 10:04, Denis Heidtmann wrote: > >> > >> On Mon, Jan 1, 2018 at 11:46 AM, Denis Heidtmann < > >> denis.heidtm...@gmail.com> > >> wrote: > >> > >>> I am looking into ways to examine the serial traffic to/from my dmm. > >> > > <snip> > > > > I found a python script intended to interface with the mas-345: > > https://github.com/markrages/py_test_interface > > https://github.com/markrages/py_test_interface/blob/master/mas345.py > > > > I gave it a try on my desktop (which has a serial port). To get it to > run > > I changed a couple of parameters and commented out one that was > generating > > a no-such-parameter error. Then I put it into debug mode so I could see > > the traffic from the meter. The good news is it appears that the meter > > does report values as the documented protocol indicates. How the > > communication is done is buried in the "serial" Python module. Someone > who > > understands Python could learn from this; I cannot. > > I've used the python serial module a few times. Looking at that code, I > see a few things that strike me as unusual. First is RTS is > cleared(line 125). Normally both DTR and RTS would be set during serial > communication. The second thing is that the meter apparently requires > the host to send 14 null characters(line 138) in order to cause it to > send its measurement data. Finally, requiring two stop bits(line 117) > is unusual. (Note that two stop bits and seven bit data is equivalent > to one stop bit and including a mark parity bit in eight bit data.) > > Since its working with the python script, I suggest you continue using > python. It's not as hard as it might at first appear. I don't recall > your goal for this, but if you look at lines 169-197, I think you'll > begin to see how it might be modified to suit you. > > galen > -- > Galen Seitz > gal...@seitzassoc.com > _______________________________________________ > PLUG mailing list > PLUG@pdxlinux.org > http://lists.pdxlinux.org/mailman/listinfo/plug > _______________________________________________ PLUG mailing list PLUG@pdxlinux.org http://lists.pdxlinux.org/mailman/listinfo/plug
