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Pastimes : Dream Machine ( Build your own PC ) -- Ignore unavailable to you. Want to Upgrade?

To: John Koligman who wrote (13178)	3/10/2002 1:42:09 PM
From: Jon Tara	Read Replies (1) \| Respond to of 14778

John, I'll take a stab at what they mean by "power" issues. The RS-232 spec calls for transmitters to swing from, (I think, don't quote me on the exact numbers!) +18 volts to -18 volts (to represent 1 or zero). The spec also calls for receivers to ACCEPT a narrower range of swing, I believe 0 and +5 (or perhaps something less than +5). (However, distance is limited when using a restricted voltage range.) Transmitters are not SUPPOSED to use 0 and +5, they SHOULD use -18 and +18. But, some designs "cheat" particularly in portable devices. Doing this saves the need for two voltage inverters and regulators. My guess is that your 520 only generates 0 and +5, and your PC's serial port isn't very happy with this. Your USB-to-serial converter is probably more tolerant. An innovative solution to the problem, BTW. I don't see any reason to go through the hassle of replacing the mother board now that you have it solved. USB parallel converters are pretty handy too - great for interfacing older printers. One less cable to plug into the back of your PC and get twisted-up. (USB hubs tend to be closer to pheripherals).