ML1400 RTU Master To Dynagen Modbus issues

Ok, so I have been wading through endless amounts of threads on this issue and I am still having no luck resolving my issue. I am trying to us a ML1400 as a Modbus RTU master to read data from a DynaGen GSC400 (Genset Controller). I only need to Read data; not write. I have verified that I can indeed connect and read data from the GSC400 with a usb/485 converter and Modscan32, which leads me to believe my wiring is fine and the issue is likely the ML1400. I am only trying to read one register for now just to establish comms. Once that is complete I will add the rest. I have tried all the usual flip the A/B lines, etc. I have tried changing every setting possible to make this work. I am pulling my hair out in frustration at this point. I am posting my program up in hopes that somebody else will find something I may be missing. The Message instruction is under LAD 9 (Generator). Any Help is Greatly appreciated!!!!

Sorry I forgot to mention I am getting error code 37 witch is a timeout....I'm sure one could derive that from my post.

Are you using the ordinary 1763-NC01 wiring adapter ?

I see that you do have the Channel 0 port configuration set up properly for "485 Network (No Handshaking)", which selects the Data A/Data B lines.

How have you connected the Data Common line ?

What's the DynaGen data map look like ? Do their addresses begin at Offset 0 or at Offset 1 ?

Do you really have multiple nodes on the network, or is the DynaGen just set for Node 11 for kicks ?

Sorry about missing the details....

I am using the nc01 adapter.

I haven't connected the data comm line to anything.

The Dyna gens addresses that I am trying to read are 40150 - 40178. It doesn't say anything in the Dyna manual as to wether they are offset or no.

This Device is the only device on the node so far with the possiblity that I will be adding one more device later on down the road. I susally always start my Modbus Chains at 11 if I don't have many devices....No particular reason other than it is easier for me to remember when I start adding multiple devices...I know where to start counting from in my head with out looking up my documentation.

The Data Common conductor has to be connected to something.

Ideally all the nodes on the network would have a dedicated Data Common conductor, but you can try connecting to chassis ground if the DynaGen unit doesn't have a Data Common terminal of its own.

With that said then can I just jumper pin 3 to pin 1 on the oragne 1763-NC01 connector then? I believe Pin 1 is chasis ground.

Data Common should be connected to something on the DynaGen that it would consider to be "Data Common".

Are the DynaGen and the MicroLogix both grounded to the same physical machine frame or Earth ground ? If so, jumpering to Pin 1 might work but it would not be as good as running an actual Data Common wire to the DynaGen unit.

A very nice little article from Chipkin Automation about RS-485 and the "2-wire" myth:

http://www.chipkin.com/rs485-cables-why-you-need-3-wires-for-2-two-wire-rs485/

Thanks Ken! I will get that rewired and let you know the results.

Ok So After checking the Modbus ports on the Dyna gen again there is an A, B, and GND. I rewired it so that the GND is directly connected to the Common on the 1763-NC01. I then re-verified with Modscan32 that I can see the data on my laptop. I am still getting timeouts on the ML1400. Is there anything else I might be missing here?

Thanks in advance!!

I have tried changing addresses. I have checked continuity on the NC01 with the documentation pinout. I have tried all of the suggestions above. anybody have any suggestions.

Just a guess because I've done it - is the 1400 using 03 function code to read the holding registers at 4xxxx?

Sometimes I've 'check box'd the 'input register' box. Which reads 3xxxx registers.

(I can't read your zipped file from this phone)

i just tried changing that to see if i get different results and no avail. I also tried the write register just for grins.

interesting though I am getting on the channel status link error code 4. which translates to .... UART error during reply reception

What is the serial framing you are using with ModScan32 ?

Your MicroLogix appears to be set up for 19200 bits per second, No Parity, 1 Stop Bit, 8 Data Bits.

That's commonly called "8, none, and 1" and it's probably the most common serial framing in the world.

But its technically not part of the Modbus RTU specification. Modbus always calls for an 11 bit frame, and the debate over whether "no parity, 1 stop bit" actually means "2 stop bits" is a long and bitter one.

I am using 19200, 8, n, 1 with a scan rate of 1000ms and a timeout delay of 6000ms on modscan32. The Dyna Gen Doc. says it only supports RTU mode and acts as a slave. Each 8-bit byte in a message contains two 4-bit hex char. The message is transmitted in continous stream with LSB of each byte of data transmitted first. The Tx of each 8-bit data byte occurs with 1 start and 1 stop. Parity check is none. Baud rates from 9.6k to 57.6k are accepted. I have tried all buad rates that the ML1400 will allow me to configure and have matched them with the Dyna Gen. I have verified continuity throughout. I have installed the comm wire. I believe I have tried every possible config. I even checked the pin out continuity of the AB 485 cable just to ensure it wasn't bad. All have had no success, But as with before as soon as i disconnect the ML1400 and ModScan to my PC i can see all data.

I am literally at a complete loss here.....

Have you tried even parity on both ends, which is always one stop bit?

I would expect A-B to support 8-N-1, but sometimes some developer reads the Modbus spec and insists on two stop bits for no parity.