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MAG8000 RS485-MODBUS RTU Communication issue

Created by: DavinderSingh at: 10/25/2013 7:13 AM (9 Replies)

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10/25/2013 7:13 AM	Rate (0)
DavinderSingh Posts: 93 Rating: (2)	Hi All, We are trying to establish communication with MAG8000-RS485 MODBUS RTU Card without success. We connected MODBUS Cards Tx, RX, Com Ports with Modbus cable to RS485 to RS232 converter. Then following are the different tries we did: A: Communication with Modscan32 software. We set all preconfigured parameters same as default of MODBUS card. Selected MODBUS RTU only as it doesn't support any TCP/ASCII. So, I thought it should work. Unfortunately, message displayed on it as " Device Not Connected". B: Then I tried to establish the communication with PDM and did the following steps to communicate over PDM: 1. Opened SIMATIC Manager. 2. Insert "Modbusnet" on net. 3. Define the properties of my PCs Com Port (1) Settings and Baud Rate (19200). 4. Define the properties of Modbus net, Setting of Comport, Baud Rate, Even, 1 stopbit. 5. Insert "Modbus device" on Modbusnet. Assign MAG8000 Basic. Named it MAG8000 Basic. 6. Upload the data from Device to PC/PG. 7. It this moment, it shows in progress followed by message: "Communication: Process Device not found." Screenshots of MODBUS with Simatic PDM.pdf attached for your review. C: Then I thought it could be problem due to RS485-RS232 conversion, so I directly took it over to Honeywell RTU with which we are going to integrate it with MAG8000. We took it directly over to RS485 Card no conversions but again "Bad Communication"-on. I'll attach screenshots in next msg. Attachment MODBUS with Simatic PDM.pdf (409 Downloads)
DavinderSingh Posts: 93 Rating: (2)
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10/25/2013 7:15 AM	Rate (0)
DavinderSingh Posts: 93 Rating: (2)	screen shots of honeywell communication is aattached here for review, Looking forward to recieve positive feedback, Regards, Davinder Singh Attachment HONEYWELL HC900 CONTROLLER.pdf (402 Downloads)
DavinderSingh Posts: 93 Rating: (2)
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10/27/2013 2:56 AM	Rate (0)
danw Gold Expert Joined: 3/28/2010 Last visit: 12/6/2024 Posts: 1095 Rating: (215)	RS-485 is devilish. The devil is in the details. 1) Honeywell's HC-900 RS-485 port is a 2 wire port, for half duplex, 2 wire RS-485. Most RS232/RS-485 converters have 5 terminals on the RS-485 side, Rx+, Rx-, Tx+, Tx- and a common, which makes them suitable for 4 wire RS-485. So there's 485 2 wire on one side, 485 4 wire on the other. What exactly have you done to get the converter to talk 2 wire? Wired jumpers from Rx+ to Tx+; Rx- to Tx-? Is there a setting (DIP or rotary switch) on the converter to force it to run as a 2 wire? 2) If it were me, I'd work at the point where you're trying with Modscan to talk to the Mag8000. Until you get Modscan to make a connection, all the other stuff is destined to failure. Keep working with Modscan until you can 'prove' the 485 link. 3) When you get to the connection up and running with Modscan and you're ready to transfer to the HC, the HC port is either 232 or 485, DIP switch selectable on the CPU module. It's possible to damage your 485 converter if the HC is setup for RS-232, because of its higher voltage levels. 4) The HC-900 needs to be a Modbus RTU master. Your configuration "set protocol for each configuration port" is currently a Modbus slave. A Modbus slave cannot talk to a Modbus slave. 5) The MBS block needs to be configured for which slave, which register, which format.

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10/30/2013 11:01 AM	Rate (0)
DavinderSingh Posts: 93 Rating: (2)	Dear Danw, Thanks for your feedback. Please refer to attached picture of RS232-485 converter used during these tests. This converter is made of 2 parts, 1st part is small 3 pin input (basically Rx , Tx , commin) from flow meter and converting it to 4/5 terminals as PCB base was showing 4 points. 2nd part of converter looks standard RS232-485 type. If I replace MAG8000 RS485 Card with RS232 card, I am able to communicate over Serial port directly using PDM, but modsan is down again. Problem with my modscan is free version open for few days. I guess it is already expired. Suggest me something more to try. Regards, Davinder Singh Attachment 201310304302-hexin.jpg (359 Downloads)
DavinderSingh Posts: 93 Rating: (2)
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10/30/2013 9:08 PM	Rate (1)
danw Gold Expert Joined: 3/28/2010 Last visit: 12/6/2024 Posts: 1095 Rating: (215)	1) The 232/485 converter: You say that the 2 wire cable is 2 wire 485 that goes to the flow meter. How do you know that? Could the 3 wires be Tx, Rx, and signal ground for RS-232? Where does the other end of the 232/485 converter go? What kind of connector does it have? Is there a DB9 on the other end that plugs into the PC's COM port DB9? Does the 232/485 converter talk to anything? Any other RS-485 device? How do you know it's functional? I'm skeptical of converters. I've lost too much time messing with defective devices. Some depend on power from the 232 port and don't get sufficient voltage. Some never work. I always 'prove' a converter before I use it on a device I know is working and functional. 2) Mag8000 with RS-232. If you can talk to the Mag8000 with PDM via RS-232, then you should be able to talk to it from either Modscan or the HC900 via RS-232. Doing so would prove the setup and then work backwards to getting the RS-485 link up and running. For RS-232: Tx to Rx, Rx to Tx, Signal Gnd to signal Gnd. Unlicensed Modscan runs only 5 minutes, then times out and has to be restarted. You can save a setup and open it for quicker testing. You need to tell it which COM port under connection > connect > connect using and do the other settings - buad rate, 8 data bits, whatever parity, 1 stop bit. I always limit "Length" to 8 or fewer registers, otherwise the screen is just too noisy. 3) Mag 8000 What is its Modbus slave address? 1? Which registers are you trying to read?

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11/5/2013 6:59 AM	Rate (0)
DavinderSingh Posts: 93 Rating: (2)	Hey Danw, Thanks a lot for your inputs, specially for MODBUS serial conversions. I wasn't aware of it properly and some cheap converter doesn't work. Now I have used MOXA TCC-80 with 2 wire input to D+/D- with shield to GND. There are 3 selector switches to select 2 wire RS485 with or with without 120ohm resister. As MAG8000 RS485 card has builtin resistor so only 2 switches in ON position. Further down the RS232 side standard 9pin connection coverted directly to USB. Opened Simatic Manager, reconfigured complete modbus device then upload the data to PC from Simatic PDM. Message appeared "Read from Device" 0 to 100% then opened PDM dialog to see all the uploaded parameters. Now I am trying to connect to modscan software, I am getting attached "Modbus Exception Response from Slave Device". I don't know whether it is ok or I still need to do something on it, to get proper response. Please advice. Thanks in advance. Regards, Davinder Singh Attachment modbus exception response.jpg (372 Downloads)
DavinderSingh Posts: 93 Rating: (2)
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11/5/2013 6:53 PM	Rate (0)
DavinderSingh Posts: 93 Rating: (2)	Hi Danw, Everything is fixed, I did little hit and trials on Modscan.. all i had to do is to reduce the length to 4 or 5 and read Holding Registers and got Slave response also. Thats the only thing I needed to show to Honeywell guy for communication. Thanks once again for support. Regards, Davinder Singh
DavinderSingh Posts: 93 Rating: (2)
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11/22/2013 10:00 AM	Rate (0)
Zhou Member Joined: 2/17/2011 Last visit: 7/12/2024 Posts: 4 Rating: (0)	my personal modbus test software but in chinese. need to change the name to .zip.001 and then open the three zip files. hope to help you. Attachment C:\Users\cn1yq190\Desktop\PI3Modbus_openby7z.001.zip (380 Downloads)
	Last edited by: Zhou at: 11/22/2013 10:13 AM
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11/22/2013 10:12 AM	Rate (0)
Zhou Member Joined: 2/17/2011 Last visit: 7/12/2024 Posts: 4 Rating: (0)	change name like zip.002 andput it in a foldertogether with the other two. Attachment C:\Users\cn1yq190\Desktop\PI3Modbus_openby7z.002.zip (349 Downloads)

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11/22/2013 10:15 AM	Rate (0)
Zhou Member Joined: 2/17/2011 Last visit: 7/12/2024 Posts: 4 Rating: (0)	change name like zip.003 andput it in a foldertogether with the other two. Attachment C:\Users\cn1yq190\Desktop\PI3Modbus_openby7z.003.zip (376 Downloads)

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