USB FTDI

[Rob_gci]

I am using a FTDI 245 USB to 8 bit parallel port converter connected to a microcontroller using the FTDI virtual com port drivers. I am using windows/CVI reading and writing over the serial com portI. would like to sample at 20 ms intervals.This entails sending a few bytes and reading the returned bytes. This setup runs for a short while but soon a fatal runtime error apears and the USB seems to lock up and the USB cable needs to be unplugged to free it or even to reboot the PC. If the sample interval is increased, the system runs for longer before errors occur. At around 100ms the errors stop and the system runs fine. Why can't I sample faster over USB as the data rate is very low?

[MarkLe]

Hi Rob,

This sounds like an issue with the FTDI virtual com port drivers really. Does the device respond to any communications using other methods (eg: Hyperterminal) once it's fatal error-ed in CVI?

What precisely is the error message you receive when the lock up occurs? Is it an error message generated from CVI or from Windows?

Have you checked with FTDI whether there are any updated virtual com port drivers?

Cheers,

Mark

National Instruments

Applications Engineer