Tim wrote: > On Tue, 2007-11-27 at 08:48 -0700, Karl Larsen wrote: >> With a volt meter I find some pins have a constant -10.7 volts on >> them which is the standard RS-232 for a no-data signal. In this static >> measure the voltmeter sees no positive volts near +12 volts. > > NB: It's quite common for serial ports on computers, these days, to be > nothing like "standard RS-232". That can be a problem for some devices > that you want to connect to it. > > I'd be trying some tests by connecting two computers together, and > seeing what you get. Or plugging in an old modem, and doing the old ATI > command tests, etc. > I thought the standard for RS-232 was +/- 3-15 volts, with a requirement that the device be able to handle +/- 25 volts. Even though you may have 15 volts on one end, you have to allow for voltage drop on long runs. I am used to seeing +/-12v and sometimes +/-5v depending on the supply available. Depending on the state of a port, I would not be at all surprised to see all negative voltages to ground. Remember, a negative voltage is a logic 1, so the status and data line will all be negative when the port is ready. (TD, DTR, RTS) Mikkel -- Do not meddle in the affairs of dragons, for thou art crunchy and taste good with Ketchup!
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