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| Thread ID: 122977 | 2012-01-25 00:05:00 | Null Modem Connections, DB-25 to RJ6 | Billy T (70) | Press F1 |
| Post ID | Timestamp | Content | User | ||
| 1255810 | 2012-01-25 21:02:00 | If you can open up the equipment, you'll probably find that the GND conductor on the serial cable (pin 7 on DB25, pin 5 on DB9, ?? on your 6-way connector) will ultimately be connected to the negative or 0V for the DC logic part of the board - hopefully easy enough to find. Then you just have 2 other lines (Rx & Tx) to choose from, so a 50:50 chance of getting it right first time! | MushHead (10626) | ||
| 1255811 | 2012-01-26 00:15:00 | Hi Team Thanks for all the help. Overnight I found a website (www.lammertbies.nl) that gave me clear information on DB25 to DB9 adapters so that I could trace the connections properly and I have now confirmed the data send, data receive, and signal ground connections (I had the latter wrong, but can't find the original reference that sent me down that path) so I now can identify the conductors in the RJ11 plug, and it also showed the purpose of the links in the DB25 connector, which confirmed the standard null modem arrangement. My next issue is the correctness of my 6-pin RJ11 plug connections. I will now set up the instrument for a download and monitor the pins with a scope to see if the data is being sent. I am pretty sure it is, because although it may just be an internal message from the instrument, IIRC, I do get a download complete acknowledgement, not a download fail. I assume that is because the instrument is using the simplest form of data transfer and has no bells or whistles so it doesn't know that it was firing blanks, however I finished so late last night my brain is fuzzy on some details. It is clear that there is communication missing because the instrument display flashes during a normal download but doesn't flash if you forget to plug the lead in, and currently it is not flashing during download attempts with the lead plugged in! So, the next step will be to open up one of the instruments again as suggested and look to see where the socket pin connections go. On reflection, I'll also try another DB9 to DB25 adapter too, I'd feel a right idiot if that had failed! It is pretty unlikely but it could happen because the old one has been plugged in and out hundreds of times, which was probably not anticipated by the manufacturer who would probably see it as a 'fit and forget' item so its durability may not be that good. No reply from the US yet either. Watch this space. Cheers Billy 8-{) |
Billy T (70) | ||
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