Ignore the USB to serial piece of the puzzle. As Brian said, it's just a serial port. Test the 9 to 25 adapter. One end will be female so it's easier to put something like the end of a paper clip into one hole at a time then put the probe on that.
Kurt On Tue, Apr 9, 2019, at 5:22 PM, Thomas Morehouse wrote: > OK - looks like I wasn't clear. In Kurt's post, he writes: > > "Take one probe of the meter and put it on pin 4 of the DB9 and the other on > pin 6 of the DB25. It should beep or light up (however you meter functions to > indicate a connection). Then do the same for the DSR line on pin 6 to pin 20. > And finally the RTS and CTS pins 7->5 and 8-> 4. If they are crossed in some > manner, then you will not get a beep or a light." > > If the usb/serial cable is a single unit (usb at one end, DB9 at the other), > how do I put one probe of the meter on the DB9 and the other probe of the > meter on the DB25? There's no DB25 on the cable, unless I plug the 9-25 > adapter into the DB9 - but then I can't put a probe on the DB9. Jeez I feel > dense. > > I'm really sorry I can't follow this, but maybe I'm just overlooking > something really simple? > > Thanks. > Tom M. > > > On Tue, Apr 9, 2019 at 7:56 PM Brian K. White <[email protected]> wrote: >> You don't check continuity on the usb-serial adapter. That isn't just a >> cable, it's really a peripheral like a disk drive or a printer, it just >> happens to be a peripheral that all fits entirely inside the plug >> housing on one end of it. There is no simple direct wire mapping between >> the usb pins and the serial pins. Between the usb pins and the serial >> pins, there is circuit board with a chip and a few other components >> which is converting and translatine between two entirely different kinds >> of signals and protocols. >> >> You treat the usb-serial adapter as just a serial *port*, and ignore >> that it looks like a wire. Just pretend it's like a serial port built in >> to the back of an old desktop. >> >> You check the continuity of the serial cable, which IS "just a cable". >> Or, really, you check the continuity of the combined serial cable with >> any null-modem and gender-changer adapters, and treat that all together >> as one "cable". >> >> -- >> bkw >> >> On 4/9/19 6:56 PM, Thomas Morehouse wrote: >> > Thanks Kurt. I'm even denser than usual tonight I guess. >> > >> > From earlier posts, seems the problem (102 screen dimming) is likely >> > caused by the usb/serial cable. One end of the cable is a usb plug; >> > other end is the DB9. >> > >> > So I'm afraid I don't know how to test continuity on the cable. I can >> > find pin 4 of the DB9 - but where does the DB25 fit in the picture? >> > >> > Or, are you saying to test the cable with the DB9/DB25 adapter plugged >> > into the cable? >> > >> > Sorry to be the dolt again. >> > Tom M. >> > >> > >> > On Tue, Apr 9, 2019 at 10:57 AM Kurt McCullum <[email protected] >> > <mailto:[email protected]>> wrote: >> > >> > There are store bought cables that work well. Brian has done a >> > great job putting together a list of those cables. For my machines >> > I have a mixture of custom made cables or slim adapters. Both >> > methods work and give me the pinout below. When you get the cable >> > right, your M102 will be happy. >> > >> > But to the question at hand, don't tear apart your cable. Check >> > it. Right now you know that pins 2,3 and 5 are all going to the >> > right locations. You will need to check pins 4,6,7 and 8. Since >> > those are paired lines (4/6, 7/8) one or both pairs will be flipped. >> > >> > If you have a multi-meter which has a continuity check on it then >> > you test both ends of the wire. >> > >> > Here is what I have found to work on all my machines and I include >> > this in the mComm manual. >> > >> > 7 Wire Cable >> > PC >> > >> > Model-T >> > DCD >> > 1 >> > NC >> > >> > >> > RX >> > 2 >> > → >> > 2 >> > TX >> > TX >> > 3 >> > ← >> > 3 >> > RX >> > DTR >> > 4 >> > ← >> > 6 >> > DSR >> > GND >> > 5 >> > ↔ >> > 7 >> > GND >> > DSR >> > 6 >> > ← >> > 20 >> > DTR >> > RTS >> > 7 >> > → >> > 5 >> > CTS >> > CTS >> > 8 >> > ← >> > 4 >> > RTS >> > RI >> > 9 >> > NC >> > >> > >> > >> > >> > Take one probe of the meter and put it on pin 4 of the DB9 and the >> > other on pin 6 of the DB25. It should beep or light up (however >> > you meter functions to indicate a connection). Then do the same >> > for the DSR line on pin 6 to pin 20. And finally the RTS and CTS >> > pins 7->5 and 8-> 4. If they are crossed in some manner, then you >> > will not get a beep or a light. >> > >> > Hope that makes sense. >> > >> > Kurt >> > >> > >> > On Tue, Apr 9, 2019, at 7:38 AM, Thomas Morehouse wrote: >> >> Thanks for the comments gents. Learn something every day. >> >> >> >> Kurt, on the "crossed wires" issue, what is the procedure for >> >> fixing the problem? I sure don't want to pull something apart, >> >> or buy even *more* adapters! >> >> >> >> Thanks. >> >> Tom M. >> >> >> >> >> >> On Tue, Apr 9, 2019 at 10:03 AM Kurt McCullum <[email protected] >> >> <mailto:[email protected]>> wrote: >> >> >> >> >> >> What you are describing happens to me when the either the >> >> CTS/RTS or DTR/DSR wires in your cable are crossed. >> >> >> >> Example. The CTS pin listens (checks for voltage) to the RTS >> >> pin on the other end. If you have a cable where RTS goes >> >> straight to RTS and CTS going straight to CTS, then you have >> >> two ends of the cable both feeding voltage to the same wire. >> >> This causes the screen to go dim. the DTR/DSR pins can >> >> produce the same issue. >> >> >> >> Kurt >> >> >> >> On Tue, Apr 9, 2019, at 5:33 AM, Thomas Morehouse wrote: >> >>> Now that I've got my usb/serial link working (M102 to Dell >> >>> laptop), I notice the 102's screen get quite dim when the >> >>> cable is in the 102's 25 pin serial port. >> >>> >> >>> Doesn't need to be connected to the Dell. Just when you plug >> >>> the usb/serial cable into the 102. Unplug the cable, 102 >> >>> screen returns to normal visibility. >> >>> >> >>> Something to worry about? or just live with it? I wouldn't >> >>> have thought the usb/serial cable chip would put such a >> >>> drain on the system. Happens with battery power, or even >> >>> with external 6 volt poweer. >> >>> >> >>> Thanks. >> >>> Tom M. >> >>> >> >> >> > >>
