Problems With USB to Serial Adapter

[Engineer@Universal]

Ok thanks alot. I can use either a Win XP or Win 7 PC so if the Win 7 doesn't work the XP should. Thanks again

[josborne]

I have also had trouble with USB-to-Serial adapters when doing communictaion at high baudrate. 

When I replaced my USB-to-Serial adatper with a PCMCIA-to-Serial card, my problems were solved. 

[LV_Pro]

And, one more thing, if this high speed communication is over any length of time there is an increasing chance of loosing data when Windows has an interrupt that is higher than the usb's. With actual serial interfaces, there is some hardware buffering that minimizes some of this, unfortunately not so much with USB. And a problem I had last year turned out to be due to the motherboard's USB ports having random "glitches" which caused the usb-serial interface, or the usb-DAQ device to  act like they had been unplugged and then reconnected. I had to put in a PCIe USB adapter (PCIe due to the lack of available slots in the computer) to resolve that problem.

[Engineer@Universal]

Ok thanks for all the input I will try a few options and see which one fixes the problem. Thanks again!

[CNCTek]

One problem that I have found with USB to serial converters is bad drivers written for them. In a couple instances I found a driver that worked back when I was having issues. The Prolific based USB serial adapters seem to be the ones that have problems and often use the windows driver way of installing. Windows also likes to write over the driver and select the best one which often times happens when you have issues and plug into a different USB port. To get around this I have found a USB to serial converter that uses its own software to emulate a COM port, which also eliminates windows messing up the drivers and over writing them. Here is the one I purchased that I've tested on Windows 7 and Vista X64 bit editions.  Link to USB to serial converter

[Engineer@Universal]

I bought one from I/O gear and it worked perfectly and I have no problems now

[CNCTek]

The IO Gear is a prolific chipset. Though it has drivers for Windows 7 and vista. It will not work for sending long files. I have found that it will start to send and then the data stream slows down and comes to a halt sometimes. Not sure why that is. On XP it does not work for PLC applications for AB where there is constant communications either. It does work for sending small files on XP. What kindof of data stream are you sending with it?

[Engineer@Universal]

I am recieving acceleration data that will be a maximum of 84 bytes long for each packet

[JÞB]

Lots of good ideas poping up but, I'm going to add five more that I've learned from PAINFUL experience

1) Computer USB ports are often the cheapest that can be mounted on the chassis and share the PC system power supply to supply USB Power.  I like the belkin powered port adaptors for clean reliable power to the device USE the wall wart adaptor and a surge arrestor.

2) High noise environments require the use of ferrites on the USB cable- and don't buy the cheapest cable either! the cheap ones are poorly shielded

3) DISABLE power management from the device manager for the USB hubs.  Windows can shut off the USB supply when it "saves energy" this shuts off the USB device if its port powered

4) PROTECT the HUB connections-  If you have a USB2.0 device and Joe User plugs in a 1.0 device in a open slot managed by the same hub- Bingo every port on the hub may back convert to USB1.0

5) especially for USB-SER.  You probably have the FTDI driver.  use the device manager to configure the LATENCY timer and PACKET size.  for small data sizes (like you have) the USB-SER convertor will introduce considerable delays.  The convertor waits for bytes to move to equal packet size before it sends them.  if a fiull packet is not buffered it waits until the latency timer expires and sends what it does have.

[CNCTek]

Good stuff, it did almost seem like it fills a buffer or something and then nothing more ever happens. Will have to check that out with my old IOGear serial USB adapter in a PLC application once. Thanks