Usb2ser

StarMan · 2009-03-01 22:12

I recently purchased two of these from Parallax.· Upon plugging each of them into a USB port there was no trouble and everything set up as predicted.·

After installation I pulled up the Basic Stamp Debug screen and typed in some gibberish and sent it to the associated com port.· The blue LED blinked rapidly for a short period (about a second) and then stopped. This made me assume that the entire string got transmitted.· For each of the two units this worked twice.· Now if I send a string I just see a s single, very fast, blink of the blue LED.· A scope on the TX line shows nothing but a steady 5 volts when I try to transmit.

Any thoughts on this.· Am I doing something wrong?

Chris I.

Mike Green · 2009-03-01 22:33

So what did you change from the time it seemed to work to when it doesn't seem to work?

You've not given enough information to help much. A schematic and a more detailed description of what works and what doesn't work and the order of things would help.

Peter Jakacki · 2009-03-01 22:46

Short answer - YES, you are doing something wrong.

As has been pointed out however we can only be specific with our answers when we have specific information. However, just a thought, you do know that if you have a USB serial port open and you unplug the USB cable and plug it back in again that it won't work properly. You have to have the port closed then plug in the USB serial then open the port. Just a guess.

Another guess you said you get a short blink but you see nothing on the scope. It could be that there is a very fast transition that you missed on the scope because the baud rate could be set very high on the USBSER. Unplug and check your settings.

*Peter*

StarMan · 2009-03-02 02:42

Mike, Peter, Thanks for your replies.· Nothing changed physically.· There is no schematic.· I only have the USB2SERs connected to USB ports. ·I am·trying to send meaningless character strings via the Debug screen and see if I detect anything on·the TX line with a·Parallax USB scope.· I did not have the scope connected when I first saw what I thought was normal.· The PC recognizes the USB2SERs as COM9 and COM10 and the respective blue LED blinks when I·transmit to each.· I set the baud rate at 9600 and other settings at 8N1 in the Debug screen and Windows Device Manager.· I've also tried every other baud rate that is available on the Debug screen.· The Parallax documentation says that Windows would prompt me for a driver but I got no prompt and, as far as I know, there is no driver to load.· No disc came with the units and there is no download from Parallax.· Device Manager tells me there is a driver loaded and that the device is functioning properly.· The driver must come with the FTDI chip.·· Is there a buffer on these that gets filled·if there is no receiver?

Chris I.

Peter Jakacki · 2009-03-02 02:52

Hi Chris,

Sounds like your PC found the driver automatically from the net or that it was installed for some other USB device that uses FTDI chips, but it doesn't load from the chip. I think the Parallax software that you installed probably installed the driver anyway.

Still, it's insufficient information or maybe it's just an insufficient test setup. Doesn't sound like you were trying to echo characters back or anything. Don't get your TX and RX lines mixed as it usually means TX from the source but sometimes that term gets used to indicate that you must connect it to TX, so in reality the pin marked TX is really an input.

*Peter*

P.S. muck about, probe the other pins.

StarMan · 2009-03-02 03:29

Peter,

It looks like you were correct in your first post.· I just wasn't seeing it on the scope.·It was too fast.

·I opened up another terminal program and typed in about 1000 characters followed by a <CR>.· The signal lasted about a second.· Plenty long enough to see it on the scope.

My bad.· Sorry to bother you guys.· Thanks for your input.

Chris I

Usb2ser

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