From: Peter Bennett
Subject: Re: Level shifter design
Date: Fri, 27 Sep 2002 10:34:10 -0700
Organization: Home for the Hopelessly Helpful
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On Fri, 27 Sep 2002 10:54:57 +0000, Paul Burke
>> I would like to design and make a level shifter to plug a GPS to a
>> RS232 port.
>> The level on the serial port of the GPS is CMOS (3.3V). SO I was told
>> that a good level shifter would be a MAX 3223 or SP3223.
>> I would like to make the level shifter myself, but I don't know how to
>> do it ( what I need, schema, ....). I have not a lot of information
>> about it.
>The advice was good (except I think the part is MAX3232), they work
>beautifully. The schematic is on the Maxim data sheet for the part, just
>get a MAX3232, a bit of matrix board, a handful of 0.1uF ceramic caps,
>and you are away! With a bit of persistence, you can even get a PCB
>mount 9 way D type into the matrix. You have to splay the pins a bit,
>but they fit.
Although the NMEA-0183 data output from a GPS receiver is TTL-ish
levels, the signals are "the same way up" as RS-232, so will work
directly with most PC serial ports.
If you want to use a Max232 or similar to get "proper" RS232 levels,
you also have to add an inverter before the MAX232, since RS-232 level
converters invert the signal, as well as changing levels.
See my GPS site below for a couple of level converter circuits.
Peter Bennett VE7CEI
GPS and NMEA info and programs: http://vancouver-webpages.com/peter/index.html
Newsgroup new user info: http://vancouver-webpages.com/nnq