MVP 2021 Joe Tauser Posted February 3, 2012 MVP 2021 Report Share Posted February 3, 2012 We are finishing up a VB6 program upgrade where we are adding a V130 using Modbus. The program was created to talk to an HP datalogger, and that instrument is still in place. It uses COM 1 on the computer. I bought a Modbus ActiveX to talk to the V130. The customer has a mix of Dell desktops and Inspiron laptops (with serial ports) so the second COM port for the V130 has to be run through a USB->Serial converter. We are using the official Unitronics Sunix -CS35 converter based on the Prolific PL2303 chipset. We have a routine that determines all the available COM ports and are able to select whatever port the USB converter assigns itself to. Now on to the problem.... During testing we found communications to the V130 to be unstable. The VB program first queries the V130 and then the HP. Communications to the V130 will work for a while and then lock up. We have to unplug the converter and then restart the program to get them back. We originally thought it was the ActiveX control, but then we swapped the V130 to COM1 on the motherboard and the HP to the USB converter and then the HP started hanging. All signs point to the driver for the converter. We are polling the devices every 5 seconds, so it's not like we're banging the ports too hard. I have installed the latest driver (1.5) from Prolific's website to no avail. I welcome any questions or suggestions to make our VB code more robust. I'm also curious if anyone has any experience with devices based on FTDI's chipset. Joe T. Quote Link to comment Share on other sites More sharing options...
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