RS485 Siemens CP341

[DLMUK]

Hi,

I had RS485 ASCII string going into a CP340 @ 9600baud rate. This was working fine.

I had to change my baud rate to 19200 so I got ripped off for a new input module, CP341, and have connected this to my PLC. I have configured using the P_RCV_RK but cannot get my string input.

I can see the RxD light flashing on my CP341.

I am taking in a raw ASCII string so I have only used the input parameters

EN_R (this is always on/set to 1, also tried with a 1s pulse but no joy)
LADDR - this is my CP341 start address (263)
DB_NO - this is my rcv DB as 26
DBB_NO - 0

DB26 is setup as

DBB0.0 String tag

Note, the config of DB26 is the same for the CP341 as it was for the CP340.

Thanks

 

[gclshortt]

https://cache.industry.siemens.com/dl/files/397/1117397/att_22929/v1/s7300_cp341_manual_en_en-US.pdf
5.4 Assigning Parameters to the Communications Protocols
You must parameterize the CP 341 and its serial interface after having entered the CP 341 in the configuration table. Have you done this?

I would try to communicate to the PC using Windows HyperTerminal and a converter from RS232 to RS485. This will prove that the signal that you are sending is valid.
http://accautomation.ca/three-free-plc-programming-software-tools/

Hope this helps,

 

[DLMUK]

Hi,

thanks for the reply. Yes I have done the params for comms protocol. Set as:

Protocol = ASCII 8/N/1

I'm only trying to receive data. I have setup RealTerm with a dummy data string contained, this then goes out via an RS485/USB converter.

No joy though

 

[DLMUK]

this is embarrassing.... the A and B were round the wrong way! I was expecting to see a permanently lit Tx light or an error but it all just appeared to work normally.

Does anyone have an example of a program which sends a command and then receives a response they would be willing to share?

I have successfully got it to send a command, then manually stopped the P_SEND_PK block and manually start a P_RCV_PK block and get it to receive but I am struggling to get this to be an automatic sequence.

Thanks

 

[KalleOlsen]

If you check your Step7 manager (file, open) you should find a bunch of example programs, one or more with PTP and CP 34x/44x program examples.

I don't have Step7 here, so unfortunately, I cannot be more specific.

Kalle