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Thread ID: 36316	2003-08-06 02:05:00	USB to serial adapter troubles	moochi (4372)	Press F1

Post ID	Timestamp	Content	User
165751	2003-08-06 02:05:00	I have a device that needs to connect to my Compaq evo n115 notebook via a serial port yet the notebook does not have one. I have installed a USB to Serial adapter but it only works intermittently. I have tested it on another notebook also and it works fine on that notebook which is essentially the same, compaq evo n800v. Both are running WinXPP. Can anyone help with why this may not be working 100%. Can I update any USB drivers on the notebook etc.... what would be different between the 2 notebooks that allow one to work and the other not!?	moochi (4372)
165752	2003-08-06 03:35:00	That's a good question, Chris . :_| Welcome to the forum, anyway . :D The serial interface implements a standard, "RS-232" . The USB interface is made to a standard, too . Unfortunately diferent implementors have different interpretations of what the standards mean . (Or in some cases, they have ignored them . ) But as soon as you get adaptors between standards, you get problems . (Even "within" a standard you get problems . . . for example the RS-232 requires plus and minus voltages (a minimum of 5 volts up to about 15) but many people get away with swings between ground and 5 volts . Some modern PCs seem to use 3 . 3 volts . . . which also works if the (PicAxe, e . g) device has a 4 . 5 volt supply, but not if it has 6v . :D I know how you feel: I'm having problems with "clever" interfaces too . But your adaptor works on one Compaq Evo and not on another . I don't know whether these adaptors generate a dual supply for RS232 or just "get away with it", but if they do, and your Compaq has less supply current available to the USB bus than the other, that could be the problem . I'll have a browse to see if I can find any other possible explanation, but in the meantime, see if you can borrow a powered USB hub and try connecting through that . If that works, let us know . That will be a Klew .	Graham L (2)
165753	2003-08-06 06:05:00	PS: "usb serial adapter problem" to google gives some good links. "Keyspan USB PDA adapter -- problem solving" (about second in list) looks worth a read. It's part of a manual , so that might be instructive reading, too. One other link gave the hint that some adapters work only at a lower bit rate than a normal serial port. (Of course, that doesn't explain your difference between two computers). Does XP (Pro?) put restrictions on "user" use of I/O ports, like the NT based Windowses? Does it work when you have Administrator privilege, and not when you do not?	Graham L (2)
165754	2003-08-06 23:36:00	Thanks for the help. I'll try a port replicator that came with the notebook that has a serial port and a separate power supply to see if that works. I'll also see if they have been set up with administrator privileges, from memory they do. Any other suggestions welcomed. I'll also have a read over the links you suggested. Thanks Graham	moochi (4372)
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