Re: Special Cable - RS232 level converters Message #4 Posted by Bill Wiese on 11 Aug 2003, 12:56 p.m., in response to message #3 by Colin
Yep, the cable has some level RS232<==>5V logic level converters in it.
You can do this with a couple of transistors & resistors & caps or do it right w/a chip.
A typical & common chip used for this task is the Maxim MAX232. I believe there is a successor called the MAX2232. Other variations (...233, etc.) also exist.
These are 'low power' chips.
The cable's electronics is likely powered from the RS232 connector. Sounds like it's just using TxD, RxD and Gnd (pins 1,2,3,7, IIRC, on a DB25 - dunno about DB9) and picking up power from another signal line like CTS, DTR, etc.... The PC application software may have to switch one of these control lines from default state to power up the electronics in the cable head.
Bill Wiese
San Jose, CA
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