>> Something that concerns me is that I don't know how to ensure which >> USB port is tethered to which comm port. Because I have 3 identical >> USB to serial adapters, its entirely possible that the comm port >> numbers will move around between the 3 USB ports everytime the >> computer is rebooted. > > Hi Dwayne, > > In my limited knowledge of Windows and USB-serial adapters: > > A USB-serial adapter should grab the same comport number each time it is > plugged into the same USB port. The port numbers will not overlap. If > you plug adapter A into USB port 1 and it is assigned com4, it will > always be com4 if it is plugged into USB port 1. If you plug it into > another USB port it will grab the next never-used-before comport number, > but plugging it back into USB port 1 it will be com4 again. A different > USB-serial adapter will grab different comport numbers. Comport numbers > stay reserved "forever" for their mated adapter/USB port combinations. > > So if you label the USB-serial adapters and the USB ports nothing should > change. Only if the adapters have a unique serial number in them. Early FTDI chips required an external SPI EEPROM into which the relevant info could be programmed, using an FTDI utility. Later chips come with unique serial numbers, but the hooks are still there to assign your own serial numbers and other identifying info that USB uses when it enumerates. > All of this works fine until you get into two-digit com numbers, then > you mileage may vary and you might consider going to the control panel > or if they are FTDI adapters they have a utility that cleans out the > registry entries and you start fresh. I understood it would work way up into 3 digit port numbers. IIRC the maximum number of COM ports is 256! -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist