Delay between Polls


Thread Starter


We are developing a telemetry system consisting of over 20 remote stations. We are using CIMPLICITY PE software and Modbus RTU plc's. The remote stations are fitted with radio units. On the computer we are using Serial Port configured as a TCP/IP connection. We are able to communcate without any problems when we are polling only one remote station (CIMPLICITY refers to this as a device). However, when we increase the number of devices to be polled, we start getting loss of data. We have found that this is coming from the polling procedure of CIMPLICITY. There is not enough time interval between changing the poll from one device to the other resulting in data corruption. Does anybody know how this can be done?
Is there another way around this problem?
You didn't say but I expect that you are using the Modbus RTU driver that is included with Cimplicity. If that is the case there may be some additional settings that are contained in one of the driver configuration files. Many of the Cimplicity components have additional settings that are not normally exposed to the user through normal user interface. Check with you GE support person to see if there are any hidden settings for the Modbus RTU driver.

If there are no settings you could try a third party Modbus OPC server. I know that Kepware and Standard Automation both have Modbus RTU drivers that allow for a delay between polls specifically for radio operation. Both these companies also allow you to control the RTS line if your radio needs to be keyed up before transmitting.

Steve Bailey

Try configuring the points to be updated based on a trigger point value. For example the trigger could be the system's seconds counter. Then you could update point 1 when seconds = 0, update point 2 when seconds = 3, etc.

Jerry Miille

If CIMPLICITY supports it, a very easy way to add delay between polls is to configure an RTS SEND delay or sometimes called an RTS ON delay.

Jerry Miille