Problems using DF1 protocol

Hi everyone,

First I would like to thank you, this forum is very helpfull, I'm glad to become a member.

I'm trying to make a Driver using the DF1 protocol, in order to ba able to communicate with Allen Bradley PlC (SlC500, Micrologix 1000).I'm developing under Visual Basic.Net using RS232 communication.

I'm currently reading the DF1 protocol, but I can't resolve some problems. I can create handle to the COM Port, but I can't communicate with the PLC, and I didn't find anywhere in the protocol what do I have to do to start communication.

If someone knows something that can help me, that would be great !

Thanks !!

Nicolas.

Take a look at this thread:
http://www.plctalk.net/qanda/showthread.php?t=10339&highlight=FREE+DF1+DRIVER

Ok, thanks but I already had it....

The dll might be helpfull but unfortunately it doesn't help me

I'm just about to finish my studies in computer software, and it's the first time I have to make a driver like this . I think Iunderstand the protocol, but I just don't know what do I have to do to start the communicating with the Allen bradley PLC which is a DH485 link by the way.

Nicolas.

I always thought DF1 and DH485 were totally different protocols. (I could be way off though)

If you are trying to communicate with a SLC via DH-485, that is the driver you should be developing, not DF1. When you try to communicate with your PLC, are you connecting to a DB-9 serial port on the SLC (if available) or to an RJ-45 connector?

I think I said something wrong, I'm trying to develop a DF1 driver and I'm connected to the PLC throw a RS232 cable.

Basically, I send a message, following the DF1 protocol, but It doesn't seem to work, I mean the number of bytes sent is always 0, and I cannot read neither.

Do I have to specify the node address ? According to the document, it can be a problem, the PLC just seems to ignore my packets.

Yes the node address must be specified, just as it is in the DF1 driver in RSLinx.

Ok, i found my problem... I was using AxMSComm object, and it seems to be the problem.. I still don't know why I cannot communicate using this object otherwise I am able to send and receive data using API function.

Thank you helping me !!!

Nicolas.