[aprssig] GPS GT-320FW(AS)

Dave B dave at g8kbv.demon.co.uk
Tue Apr 23 07:27:25 CDT 2013


On 21 Apr 2013 at 16:03, Steve Noskowicz wrote:

> 
> Yea.  That datasheet is woefully light on it's info.  Interesting
> since I would "tend" to believe the TTL levels it has are the phase
> that is inverted from RS232.  This would make for simple interfacing
> with local logic without requiring two a 232 level converters.
> 
> ...  but you never know.  The UniTraQ site is no better with dead
> links to datasheets. ... sigh...
> 
> Surely Scott will chime it...

Come on guys, this isn't rocket scienct....

Has everyone forgotten how to think through an issue, or search online?


http://www.interfacebus.com/voltage_threshold.html

http://www.interfacebus.com/voltage_interface.html

http://www.interfacebus.com/Design_Connector_RS232.html

(Just one load of hits from Google.....)


TTL to/from RS232 at least sub 10's of kbits/second has been done to 
death.  You can use just one NPN transistor (and some passives) for the 
incoming '232 to TTL, and similarly, one PNP device (and a -ve rail) for 
the outgoing "driver".  More than good enough for short cables as found 
in most shacks, and suprisingly good at lower speeds on longer cables at 
lower speeds.

If you've no conveniant -ve voltage, that's trivial to produce too, 
either from a suitable clock and charge pump, or from the data line and 
charge pump!

Yes, by convention, the data lines in-to/out-of chips like UART's are 
inverted from the RS232 line in the outside world, that is normal, and 
makes the interfacing relatively easy.

Next question, who remembers what U A R T actually stands for?  I would 
expect most here should.

73

Dave G0WBX.



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