Thanks Kurt. Testing the DB9-DB25 adapter only - not the usb/serial cable - I have continuity NOT from pin 4 of the DB9 to pin 6 of the DB25. I have continuity from pin 4 of the DB9 to pin 20 of the DB25. That's using the numbers printed at the pins themselves.
Should I even bother testing the others you suggest? Sounds like the adapter already fails the test. Tom M. On Tue, Apr 9, 2019 at 8:48 PM Kurt McCullum <[email protected]> wrote: > 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. > >>> > >> > > > > >
