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ELCouz
Joined: 18 Jul 2007
Posts: 427
Location: Montreal,Quebec
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| [OT] Advice for RS485 |
 Posted: Wed Aug 03, 2011 11:04 am |
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Hi,
Off-topic i know but lot of knowledge around this domain.
I'm currently trying to interface my Mini6410 (ARM) running on Windows CE.
The problem is that i need a RTS signal to drive the rs485 chip ( DE and RE pin) and TTL serial ports on the device have only TX and RX...
Or in another way to see the problem a have a device which only have RX and TX lines with no possibilities to output additional signal to drive DE and RE pins...
On the other side, my slaves the pics  have no problems to be interfaced with the rs485 chip since they have many configurable I/O pins beside RX and TX pins!!
What would you do with this problem?
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Regards,
Laurent
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Here's my first visual theme for the CCS C Compiler. Enjoy! |
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SherpaDoug
Joined: 07 Sep 2003
Posts: 1640
Location: Cape Cod Mass USA
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| Posted: Wed Aug 03, 2011 1:08 pm |
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A common way to deal with this is to have the Start bit trigger a non-retriggerable one shot that times out in the latter part of the Stop bit.
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The search for better is endless. Instead simply find very good and get the job done. |
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ELCouz
Joined: 18 Jul 2007
Posts: 427
Location: Montreal,Quebec
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| Posted: Wed Aug 03, 2011 1:19 pm |
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| Quote: | | A common way to deal with this is to have the Start bit trigger a non-retriggerable one shot that times out in the latter part of the Stop bit. |
That look a little bit complicated (library for comport on windows ce are simple and send only ASCII chars, no configuration beside baudrate) ...
one thing i though is to make the whole thing full duplex using 4 wires instead of 2...
Make one chip always TX and the other always RX.
Or another way maybe a little bit overkill is to relay the TX RX from arm device then process it through a small pic to the rs485 chip...
Don't be shy if you have more ideas 
thank you very much!
_________________
Regards,
Laurent
-----------
Here's my first visual theme for the CCS C Compiler. Enjoy! |
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ELCouz
Joined: 18 Jul 2007
Posts: 427
Location: Montreal,Quebec
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| Posted: Wed Aug 03, 2011 1:25 pm |
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one thing i'm afraid is the way rs485 communicate between chips.. i'm stuck with a ASCII send/receive device for now... i think it require binary mode or something looks like it need a 9-bit communication for the addressing right?
I need to read more on that...
Thanks!
_________________
Regards,
Laurent
-----------
Here's my first visual theme for the CCS C Compiler. Enjoy! |
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bkamen
Joined: 07 Jan 2004
Posts: 1617
Location: Central Illinois, USA
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| Posted: Thu Aug 04, 2011 5:12 am |
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| ELCouz wrote: | one thing i'm afraid is the way rs485 communicate between chips.. i'm stuck with a ASCII send/receive device for now... i think it require binary mode or something looks like it need a 9-bit communication for the addressing right?
I need to read more on that...
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Only if you want addressing. But you can also design packets that contain source/dest addresses if on a multi-drop bus.
I just did an RS485 project using binary.
You just have to think about things a little differently.
-Ben
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