Siemens PLC to Beta Laser micrometer - wont talk? 1

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I am trying to configure a Siemens cpu315-2-DP to a Beta laser micrometer through an rs-232 communication interface (ASCII format). I have checked all the communications parameters such as baud rate, stop bits, and parity to be certain both plc and communications partner are the same. I have been able to communicate successfully between the plc and a laptop computer (using Hyperterminal) and between the communications partner (the laser micrometer) and the laptop (again using Hyperterminal). Both communications interfaces are working and setup properly, proven by Hyperterminal. I don't have to change any parameters to go from the plc to the laser mic. communicating with the laptop. Further, because the plc and laptop are DTE equipment, the wires on pins 2 and 3 of the rs-232 interface cable must be crossed for the interface to work. On the other hand, the laser mic. requires a straight through connection (null modem – as I refer to it), meaning pins 1 are connected on both DB 9 pin connectors, pins 8 are connected, pins 7, ... , pins 1 are connected.

I have attempted communicating with the venders, but as soon as either vendor hears that their device is able to communicate with the laptop, they start pointing in the direction of the other vender. I have tried a "null" modem connection with the plc and the laser mic. – that doesn't work at all (plc transmits but doesn't receive anything from the laser mic.). However, when I use an rs-232 interface cable (pins 2 and 3 crossed from one connector to the other), the laser mic. responds but the information is garbled. So in this case, both my transmit and receive leds are operating.

If anyone has experienced this incompatibility or has a suggestion which could point me in the right direction, I would appreciate some help.

Thanks for your attention.

 

[JustAnEngineer]

Hi,

Some time ago I have used Opto22 using their serial daughter card to communicate with the Lasermike 282 processor and have created an Excel application for library programming. With regards to Opto22, I used three conductors as you have with Hyper Terminal. I have seen garbled messages plenty of times. The settings I had used was COM1:38400,N,8,1,CTS. I recall if you dont clear out the buffer on the control side you will more than likely always get meaningless results back. Most of the commands I used were basic ones like Run/Stop(500), SPC On/Off (502). Let me know if you are still having issues.

 

[jbartos]

Suggestion: Beside traditional software interfacing parameters, the hardware parameters also have to be compatible.
Contact the Siemens and Beta Laser Micrometer manufacturer tech supports.

 

[carlsorj]

RS 232 typically required hardware and/or software handshaking. A quick way to fake this is to tie back the hardware handshake bits. Typically CTS to RTS and DSR to DTR. B&B electronics has great reference material for this. Then you can connect the TD and RD pins appropriately (2 to 3) and see if the fake helps. If you really want the handshake, go back and start connect CTS and RTS first then the DSR and DTR or visa versa.

Hope this helps.