FX1S COMMUNICATIONS THROUGH PROGRAM PORT

[Patriot]

I am looking for information on the protocol for communicating to a Mitsubishi FX series PLC (In particular the FX1S). I was hoping to write a smal VB program to communicate directly through the program port of the PLC. The more I look at documentation and Mitsubishi manuals, the more confused I get. I see a number of communications options, but many of them require additional communications boards for the PLC. I do not want to do this, since I am keeping the cost of this system low. I also am not looking for any third party Active X controls. I want to write the protocol driver myself, since this is a very simple application where I would like to read up to 10-15 registers from the PLC and display them on a screen on a computer. I know I can connect using GX Developer and read data, but this is intended for maintenance personnel who don't want to spend over $1,000 for a copy of GX Developer to monitor data. The most I want anyone to have to buy is a progamming port cable that will interface to their laptop, such as the SC-09 from Beijers. I cannot seem to find anything that clearly explains the protocl required to do this. I have seen info on the RS command in the PLC, etc. The FX Data Communications manual has a section called "Programming Communication", but it does not go into any detail of the protocol. Am I looking in the wrong place? Is there documentation available for this protocol? I know that with the Allen-Bradley PLCs, I can easily program the serial DF1 protocol to connect to the programming port of a PLC like an Micrologix using a Visual Basic program on a PC. I can easily do this to a Modicon, etc. using the easily available documentation for Modbus. Is there something that documents this information as well for Mitsubishi? If someone has any idea, I would appreciate it.

[panic mode]

check download section on this forum, there is quite readable QBasic example

[TimWilborne]

Normally with AB you will use an intermediate software such as RsLinx and program the VB with DDE or OPC. Some people do "roll their own drivers." Are you looking for software or to create your own driver? TW www.twcontrols.com

[Patriot]

I am looking to create my own driver within my own "HMI" program that I will build using VB6 or VB.NET. What I am looking for is a description of the protocol format that would be used to create the proper instructions to transmit to the programming port of a Mitsubishi FX PLC to read register data. I do not see anything that clearly shows this. I have seen some protocol descriptions, but most seem to be setup for other connections. I am a bit confused about topics such as Computer Link, N:N, etc. I am under the impression that to connect to the programming port of the FX, the "Programming Port" protocol is required? I am a bit confused by all of the various Mitsubishi protocols and where they are applicable and where they are not. I have looked at the QBASIC download, but I would prefer to start with a Mitsubishi description of the protocol rather than rely on someone else's program. Obviously the QBASIC programer found some protocol documentaion somewhere that applies. However, the basic code does not indicate what Mitsubishi PLC was connected in that example or how it was connected. Perhaps this protocol is not documented by Mitsubishi?

[Sergei Troizky]

I would use DDE driver. Make search on MelDDE.

[TimWilborne]

I would have to agree with Sergei. Do you plan on doing lots of these? Just wondering why you wish to create your own. I guess if you were distributing it on many machines it may be worth it but on a small scale I think you would end up with a lot more time in it.

[Crossbow]

MELDDE is old. The current communication architecture is MX-Component. It gives you communication commands in an ActiveX format you can use in VB and VC++.

[Sergei Troizky]

And what? Let's judge it's ability to perform the task required. It has nothing with age.

[Crossbow]

I was just stating it is based on old DDE technology, not like the new OLE and OPC stuff. It still works, I didn't mean it's not a valid option. But I am fairly sure it is not set up for the latest PLCs, newer addressing structures, and the latest communication options, like FX3U over Ethernet.

[TimWilborne]

VB.net does not support DDE. Yes you can still use VB6 for DDE but many companies specify the use of VB.net Also MELDDE is not approved for running on Windows XP. Looks like Windows 2000 was the last supported

[waynes]

Hi guys, The easiest way to this is to use MX Components. This uses COM DCOM and OLE interfaces to do the raw comms to the PLC. Also, you can setup any type of connection to the PLC and use one name. You simply adress this name and then always connect to it.

[panic mode]

they both work but MC Components is my preference too. ActiveX performance beats the DDE and so far I've never seen anyone asking for PLC to do less, they always want more and more. Also PLCs will be around for long time but PCs age so fast.

[FNMdeJong]

The communication protocoll of the FX series is no open protocoll. So when searching on the internet you probably wil not find it. You can always re-engineer the protocoll by a protocoll analyser, it is just a serial driver. When using DDE connections and transfering for a long time data between PC and PLC it will surely chrash. Why do you want to write your own driver, while it is only for one low cost machine??? The time you spend on developing is much more than when you use MX-Components. In that case you have the complete driver functionality ready to implement in BV6, VB.Net, C++. It is not so expensive.

[Patriot]

Thank you. I think you answered the question. I have tried many searches for information on the FX protocol. I think that this might be the "monitor interface protocol" referred to by some. Anyhow, I cannot find anything but information on controls that can be purchased to handle the communications, and references to an old basic program. I have looked at the MX Components software, and it seems reasonable (when compared to other similar programs that cost close to $1,000 US). I will have to see if I can purchase this. The only issue I now see is whether this control can be distributed as part of a Visual Basic app on more than one PC. Many of these controls are limited to a single machine.

[Crossbow]

Licensing is typically per copy, so if you sell your program to 5 users, you would need to buy 5 copies. As for the front port protocol on the FX, it's a proprietary protocol which Mitsubishi does not release to the public. So MX-Component is your best bet.