I bought a GN801 GPS module from Stoton
( http://www.stotoncn.com/gnssmodule/showproduct.php?lang=en&id=42 )
Power supply range is +5V.
There is an onboard MAX3232CAE that is supposed to output RS232 signal.
I need to connect this module to a third party system that only accept RS232 with -12V / +12V signals levels.
When viewing MAX3232CAE TX pin trace with an oscilloscope, i can see it outputs -6V / +6V signal.
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Wasn't MAX3232 supposed to output -12/ +12V signal, did i miss something here ?
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This GPS module also exists in version with TTL output rather than RS232, if i go with TTL outputs (0-5V) how could i get a real -12V / +12V RS232 output since MAX3232 looks not to do so ?
Thank you very much for your lights on this and best regards,
Best Answer
You will need to supply details of that device, and a copy of the documentation which leads to the conclusion that it requires those signal levels. That requirement is not part of RS-232.
Good.
No, the MAX3232 datasheet shows that it outputs a minimum of +/-5 V (with 3k load) which meets the RS-232 specification (see TIA/EIA-232-F paragraph 2.1.6).
+/-12 V is not "real" RS-232. Even a very old RS-232 driver, like the MC1488, is not guaranteed to output +/- 12 V. Although it would be possible to achieve those signal levels, it might require a design using discrete components or boosted power rail voltages for an old RS-232 driver.
In the distant past, +/-12 V was a common maximum RS-232 voltage level seen in real life. Perhaps the documentation you have for that "module" has been mistranslated or otherwise misinterpreted that this voltage is a requirement...