06-29-2012 07:50 AM
Hi! We ve just bought LeCroy scope Wavejet 354A. I m trying communicate with the scope using the official driver downloaded from NI web site. In our case we have no optional LAN or GPIB cards and only USB port is installed and used. Using the usb driver from the CD I could built virtual COM port and indeed I can communicate with the scope but It takes really a lot of time to transfer the data from channel (let’s say channel 1) to the pc. For example to transfer the data can easily take about ½ s o so.
Even when I used 10 years old LeCrpy scope with GPIB the communication was pretty fast. My question is does USB port has some limit and the transferring of data is slow because of specification /realization of that USB->Virtual Com port. Should we buy an optional LAN card ? This is only one way how to increase the communication speed?
06-29-2012 09:25 AM
I'm not sure why you would not be talking to LeCroy about this instead of NI.
Of course there is a limitation. You don't mention which baud rate you are using but even at the fastest (115k), you are operating at about 1/10th the 1MB/s rate of GPIB. If you wanted fast, you should have made sure the vendor implemented USBTMC. There is a price you pay for going cheap. Buy the LAN or GPIB if you want fast.
06-29-2012 09:30 AM
For us were very surprising that USB port of the scope is not really USB. Company does not provide USB driver it provides connection via Virtual COM port which is very limited.. But I did not expect that LeCRoy does not have a normal usb driver..
06-29-2012 09:57 AM
That's why it is important to read the fine print. With USBTMC or any other USB class than com, the vendor would have to also write some custom software for a user to communicate (or depend on the customer to write it himself). The USB driver is also a bit more complicated. With a com port, a user can just use readily available terminal emulation programs to communicate.