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JPH
Joined: 02 Feb 2005
Posts: 9
Location: Finland
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| RS232 -> RS485 Conversion |
 Posted: Wed Nov 09, 2005 8:53 am |
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Hello
What would be the easiest way to connect RS232 device(PC) to Full Duplex RS485 device(camera). Does easy resistor divider work or do I have use PIC and make the code to handle RS485 Enable pin. Have anyone tested MAX3162 chip? I readed datasheets and I understood that it will handle RTS signals by self.
Any suggestions??
Cheers
Jussi |
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Neutone
Joined: 08 Sep 2003
Posts: 839
Location: Houston
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| Posted: Wed Nov 09, 2005 9:08 am |
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| B&B Electronics (http://www.bb-elec.com/) makes a number of adapters to connect a PC to an RS-485 network. The preferred method of connection is to use a RS-232 serial port built-in to a computer and convert that to RS-485. Unfortunately most new computers do not have a built-in RS-232 port. In this case the best solution is to use a USB to RS-485 converter. For best results optical isolation is also recommended. Both types of converters are available with optical isolation. |
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jds-pic
Joined: 17 Sep 2003
Posts: 205
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SherpaDoug
Joined: 07 Sep 2003
Posts: 1640
Location: Cape Cod Mass USA
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| Posted: Wed Nov 09, 2005 12:56 pm |
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It definately takes some sort of smarts to convert between RS232 and RS485. A simple resistor network won't do. Some converters are nothing more than a level shifter and a one-shot to run the TX enable line. Others are more sophisticated.
_________________
The search for better is endless. Instead simply find very good and get the job done. |
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William H. Conley III
Joined: 27 May 2004
Posts: 17
Location: Tucson, AZ
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| Posted: Fri Nov 11, 2005 10:20 am |
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Is the RS232 TTL ?
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- Bill |
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asmallri
Joined: 12 Aug 2004
Posts: 1634
Location: Perth, Australia
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| Re: RS232 -> RS485 Conversion |
| Posted: Fri Nov 11, 2005 10:24 am |
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| JPH wrote: | | What would be the easiest way to connect RS232 device(PC) to Full Duplex RS485 device(camera). |
Are you sure the camera is RS485?
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Regards, Andrew
http://www.brushelectronics.com/software
Home of Ethernet, SD card and Encrypted Serial Bootloaders for PICs!! |
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SherpaDoug
Joined: 07 Sep 2003
Posts: 1640
Location: Cape Cod Mass USA
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| Posted: Sat Nov 12, 2005 2:30 pm |
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| William H. Conley III wrote: | | Is the RS232 TTL ? |
Strictly RS232 is not TTL. It has several variations but generally it uses +/- 10V to +/- 15V. Some RS232 interfaces will accept TTL levels but it is not recommended.
When CCS refers to "RS232" they mean serial communications which enter and leave the PIC at TTL levels. How you manage the proper voltage levels is not a concern of the compiler. One thing the compiler does assume is that the voltage converter will invert the signal, as all converter chips I know of will do. If you are not using a converter chip the software UART allows you to use the "INVERT" command to do the inversion in software instead of hardware.
_________________
The search for better is endless. Instead simply find very good and get the job done. |
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Ttelmah
Guest
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| Posted: Sat Nov 12, 2005 4:09 pm |
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Yes. This has been moaned about recently too.
However I think the 'question', was trying to raise the legitimate point that it is easier to do TTL serial to RS485, than to do RS232 to RS485 conversion, and that if the serial was at TTL levels, this might alter the answers.
Best Wishes |
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