RS485

Hi groups, Now I have a DB9 Rs232 to Rs485 Serial Converter , but no sepecification. How can I know which pin is RS485+ and which pin is
Rs485- .....and so on. I will appreciate every reply.
Thanks and best regards! LiuDuan
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Contact the manufacturer of the converter. In my experience, there is no standard pin usage for RS485 (or RS422 either).
On 6 Oct 2003 02:15:01 -0700, snipped-for-privacy@jyintl.com (windawn) wrote:

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Also check the manuals to item(s) you are connecting to. RS485 is normally a multidrop system and may also require a terminator. GE PLC's use it and have configurations in their online manuals.
(windawn) wrote:

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RS485 is not well documented by most vendors, as your ignorance plays into their products sales goals quite nicely. However, there are some very excellent resources you can read about RS485. Then you can 'jam-up' the vendor of choices as to why their product(s) are so hard to use. I avoid Windoz based gui crap, that you'll discover later on, once you master RS485......
Also, RS 485 can be redered( available) on a product via hardware base, i.e. it's in the chipset, or software, i.e. its in the firmware, or a combination of both. The best things is to discover how the vendor implemented RS485 on their product. Most vendors do not give up this information, readily, because they have done a shitty job in there RS485 offering(s). Once you figure out what chipset they used to partical or fully implement RS485, you 1/2 the way home to reverse engineering their mess.
Circuit Cellar publish an article called "RS-485 Netowrk for Embedded System" and is a most excellent starting point. Search out silicon vendors that offer RS485 chipsets, is also and excellent exercise.
WE most often build our own boxes, i.e. RS485 2 and 4 wire interfaces plus microcontroller, and then get each and every vendors RS485 device to work with a box that we write assembler or ANSI C on. If you only have a few devices that need to talk RS485, then canned vendor based products may work. If things do not work then you have to build a hardware based sniffer for RS485. When a vendor (and this is rare) does offer a built in RS485 sniffer, it was usually develop by the same engineer (usually a clueless EE that cannot code) that integrated the RS485 device into the product.
We use a combination of EEs, Computer Engineers and Mostly Computer Scientist to develop software. Companies that mostly use EEs to write software specification and code, are usually clueless.....
BEST of Luck!
James Horton, PE snipped-for-privacy@buffer.net
mindspringnews wrote:

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Also try Black Box web site for insight. http://www.blackbox.com/tech_docs/tech_docs_index.html
and
http://www.bb-elec.com/cheatsheet /
http://www.rs485.com /
(windawn) wrote:

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