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USB/MPI cable no support for profibus, please help

Created by: Zer0 at: 7/24/2011 7:04 PM (5 Replies)

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7/24/2011 7:04 PM	Rate (0)
Zer0 Regular Member Joined: 6/15/2011 Last visit: 12/4/2024 Posts: 25 Rating: (0)	Hello, my Siemens USB MPI cable broke and I didnt feel like spending another $500 on it so i bought one off of Ebay for $40, now it turns out that this is only MPI does not support profibus. I have to go all the way to PLC take off the profibus connector and then connect the cable directly to the CPU 314 to be able to go online with it, I can not do it from the HMI end. I think it has something to do with the cable not getting power. Is there a way I can modify the cable to make it work with profibus? On ebay this is what they had for long distant communication, but i'm confused a little. Long-distance communications: For USB/MPI+, the largest communication distance is up to 1000m at the communication speed of 187.5Kbps. It needs to splice 120ohm terminal resistance between 3 and 8 pin on the RS485 port(DB9 Male) to eliminate signal reflection, and connect 24VDC power between 7 and 2 pin. But requires one PFB-G for each PLC. any help will be appreicated.

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7/24/2011 10:45 PM	Rate (0)
dchartier Grandmaster-Expert Joined: 9/27/2006 Last visit: 3/21/2025 Posts: 12344 Rating: (2707)	Zer0 Hello, my Siemens USB MPI cable broke and I didnt feel like spending another $500 on it so i bought one off of Ebay for $40, now it turns out that this is only MPI does not support profibus. I have to go all the way to PLC take off the profibus connector and then connect the cable directly to the CPU 314 to be able to go online with it, I can not do it from the HMI end. I think it has something to do with the cable not getting power. Is there a way I can modify the cable to make it work with profibus? On ebay this is what they had for long distant communication, but i'm confused a little. Long-distance communications: For USB/MPI+, the largest communication distance is up to 1000m at the communication speed of 187.5Kbps. It needs to splice 120ohm terminal resistance between 3 and 8 pin on the RS485 port(DB9 Male) to eliminate signal reflection, and connect 24VDC power between 7 and 2 pin. But requires one PFB-G for each PLC. any help will be appreicated. Could you please give us more info on the USB-MPI adapter you bought? Make and model would be good, any web link for details would be better. Hope this helps, Daniel Chartier

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7/25/2011 1:33 AM	Rate (0)
Zer0 Regular Member Joined: 6/15/2011 Last visit: 12/4/2024 Posts: 25 Rating: (0)	Sure, here is the ebay link where i bought it from http://cgi.ebay.ca/OEM-Siemens-S7-300-400-USB-MPI-PLC-Programmer-Cable-/150610908963?pt=LH_DefaultDomain_0&hash=item23111c1723#ht_3236wt_753 it seems to be manufactured by some company in china named DGYCGK hope this helps. Thank you

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7/25/2011 2:14 AM	Rate (0)
fritz Diamond Expert Joined: 10/7/2005 Last visit: 3/20/2025 Posts: 3042 Rating: (1061)	Zer0 Is there a way I can modify the cable to make it work with profibus? Hello Zer0 I don't have any hands on experience to offer for your choosen Adaptor, but say the description onebay is pretty clear when it states that: "1.) Double-click on "PC Adapter (MPI)" to set the parameters of COM port and MPI port. The adapter does not support "PC Adapter (PROFIBUS)" option"
	Cheers fritz The advice and opinion given in this thread is that of the author and does not necessarily reflect the views of I S Systems Pty Limited. To find out how I S Systems can help you with your automation needs please visit www.issystems.com.au.
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7/28/2011 4:09 PM	Rate (0)
Zer0 Regular Member Joined: 6/15/2011 Last visit: 12/4/2024 Posts: 25 Rating: (0)	Is it possible to use Ethernet cable to monitor/programm S7-300 instead of MPI cable? Thank you

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7/28/2011 5:03 PM	Rate (0)
dchartier Grandmaster-Expert Joined: 9/27/2006 Last visit: 3/21/2025 Posts: 12344 Rating: (2707)	Hello Zer0; Yes, it is possible (and easy)to download/monitor your PLC over Ethernet, if you have an Ethernet interface (CP 343-1, or Profinet interface on the CPU) setup and configured. There are many threads on the forum concerning this issue, such as this one: /tf/WW/en/Posts/24064 Hope this helps, Daniel Chartier

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