On 12/16/2012 3:05 PM, Viesturs Lācis wrote: > 2012/12/16 Dave<e...@dc9.tzo.com>: > >> Be careful. RS232 is not ttl compatible. RS232 is bipolar voltage based >> and ttl is not. >> >> You can get RS232 to ttl converters and converter chips. As well as >> RS422 to ttl converters and converter chips. >> >> > Then I am messing something up with all those standards. It takes > differential signal and converts it to single-ended. > >
You probably know most of this stuff... but ...just to recap. If you look at the scope diagram in the lower right side you will see that although RS232 is single ended (not differential) the voltage swings both + and -. http://en.wikipedia.org/wiki/RS-232 RS422 is different obviously.. http://en.wikipedia.org/wiki/RS-422 TTL is something entirely different http://en.wikipedia.org/wiki/Transistor%E2%80%93transistor_logic I have used encoders that use TTL and RS422 standards, but I am not aware of any that use RS232, however some encoders have a single ended 0-12 volt or so output. I've been burned on this stuff several times due to reading too quickly.. etc. The latest was a serial interface on a chip that used RS232 type serial data encoding , but at TTL levels. That is pretty common for chip level devices. Using that device with a RS232 PLC interface was a no go. The fix was to add a RS232 to TTL level adapter chip. I looked at the 7i39 encoder interface and it is not clear to me if that is a TTL interface or a single ended 0-5 volt voltage interface.. I bet it is a 5 volt TTL interface which would not work reliably with a RS232 driver. Peter... what is it? Dave ------------------------------------------------------------------------------ LogMeIn Rescue: Anywhere, Anytime Remote support for IT. Free Trial Remotely access PCs and mobile devices and provide instant support Improve your efficiency, and focus on delivering more value-add services Discover what IT Professionals Know. Rescue delivers http://p.sf.net/sfu/logmein_12329d2d _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
