# Not the usual AB to VB question...

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#### Don

There is a lot of information for talking DF1 or DH+ to allen bradley PLCs via visual basic. But, I have found information on the DH-485 protocol used by the low-end SLC's to be more elusive. Does anyone know where this might be found?
I'm trying to interface a SLC 5/01 to VB via a 1747-PIC. In theory, this should work, right? I would like to find a subroutine or ActiveX control that would handle the networking end of things. Any help or suggestions would be GREATLY appreciated as my forehead is developing lumps from the repeated wall-bashing. Thanks!

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#### Eddie Willers

You don't find VB examples of DH-485 protocol because the timing precision for Tx/Rx control of the multidrop bus is impossible for VB. You'll find numerous discussions on this board and others about why it's difficult for even a low-level device driver to perform, especially in Windows.

You might find an inexpensive DF1/DH485 microcontroller-based gateway; there are some (like IDEC's DF1DH485GW, about $150 USD) that pass only the data-table read parameters and aren't useful for uploading and downloading ladder logic. Then you can use just the DF1 example code or ActiveX tools. The full-on DH485/DF1 gateways like A-B's 1770-KF3 or 1747-KE are just too bulky and expensive for a project involving a lowly 5/01 controller. B #### Bill Sturm A-B considers the DH-485 protocol to be proprietary. Bill Sturm S #### Steve Myres, PE Would it be easier to spend$300 and put in a MicroLogix, which has DF1 natively?

[email protected]

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#### Jeremy Pollard

Initially and still does (TMK) the SLC uses a compil;er/decompiler to treat the code so that you MUST have the license to interface. Reverse
engineering wont work (again TMK) For data access the exercise should be simple since it is a serial connection but programming stuff would be formidable.

Cheers from:

Jeremy Pollard, CET
The Crazy Canuckian!
Integration, Automation, and Training

On The Web - http://www.tsuonline.com
PLCopen North America - [email protected] www.PLCopen.org

8 Vine Crescent, Barrie, Ontario L4N 2B3
705.739.7155

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#### Jiri Baum

Don:
> There is a lot of information for talking DF1 or DH+ to allen bradley
> PLCs via visual basic. But, I have found information on the DH-485
> protocol used by the low-end SLC's to be more elusive. Does anyone know
> where this might be found?

Is that the same as used by the SLC 5/05 and the PLC5 family? If so, ABEL (Allen-Bradley Ethernet Library) might help... it's written for Linux, but
it shouldn't be that difficult to port or at least use as a guide.

The author is Ron Gage, "[email protected]", mailto:[email protected]

> Any help or suggestions would be GREATLY appreciated as my forehead is
> developing lumps from the repeated wall-bashing.

tlhIngan SoHchoH'a' ? (Sorry, Star Trek joke.)::

Jiri
--
Jiri Baum <[email protected]>
http://www.csse.monash.edu.au/~jirib
MAT LinuxPLC project --- http://mat.sf.net --- Machine Automation Tools

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#### Joe Jansen/ENGR/HQ/KEMET/US

The 5/01 is a modular processor. Therefore, unless there is only 1 input and 1 output module in the rack, a Micro would not have the I/O capacity to replace the system. Plus, the \$300 upgrade is a myth that was dispelled a week or so ago. No upgrade can be done for only the price of the processor.

DH-485 is a closed protocol. Your best bet is a converter (such as the PIC) and an activeX control, readily available from several sources. do a google search, or check the archives of the list.

Your choice of operating system is going to affect how well the communications work. You may consider buying RSLinx (not the free version)
with DDE support. I have used that successfully to communicate thru a DDE link into a VB app. That is, of course, dependant on how much data you
need to move back and forth.

HTH

--Joe Jansen