Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uwm.edu!cs.utexas.edu!tut.cis.ohio-state.edu!pt.cs.cmu.edu!andrew.cmu.edu!kg19+ From: kg19+@andrew.cmu.edu (Kurt A. Geisel) Newsgroups: sci.electronics Subject: Using MC1488 for TTL->RS-232 Message-ID: Date: 30 Dec 89 06:00:34 GMT Organization: Class of '92, Carnegie Mellon, Pittsburgh, PA Lines: 31 Help a poor non-EE : I am trying to convert a TTL signal into an RS-232 signal. I was under the impression that this can be done simply with the MC1488 monolithic quad serial line driver. Here is my set-up: 2 |----------| 3 TTL ---------->| |---------> RS-232 1 | MC 1488 | 14 -5 V --------->| |<--------- +5 V 7 | | GND ---------->|----------| What I get: When the TTL input is at 0 V, the RS-232 output is at 3.25 V. When the TTL input is at +5 V, the RS-232 output is at 3.94 V. Needless to say, this is useless. All the power supply lines have been check and re-checked. Do I have a bad chip or am I missing some glue? Any help would be greatly appreciated, - Kurt Kurt Geisel SNAIL : Carnegie Mellon University 65 Lambeth Dr. ARPA : kg19+@andrew.cmu.edu Pittsburgh, PA 15241 UUCP : uunet!nfsun!kgeisel "We just need to short-circuit the continuum on a BIX : kgeisel 5 or 6 parsec level." - Forbidden Planet