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I hope I'm asking this in the right place, I didn't know if it should go on stack exchange or super user instead.

Problem Summary: I need to configure the baud rate of a USB to Serial bridge device.

What I need to use them for: I need to send commands to some other serial device at different baud rates through hyperterminal, using a PC without a serial port.

About the bridges: The only identifying marks other than on the IC is a url which has been no help. The bridges have very little on the PCB except except one chip and a few resistors etc, so I investigated the IC, a Silicon Labs CP2102, (datasheet) and came across more information:

What I've done so far: I bought two to test them communicating to each other. I performed a simple test, (obviously using their default baud rate), as follows:

  1. Install Silicon Labs Silicon Labs CP210x USB-UART VCP Driver Kit
  2. Insert the two USB-Serial converters into a PC, (Running windows XP)
  3. Connect RX pin of one device to the TX pin of the other, and vice versa
  4. Open device manager, note the two new COM ports
  5. Open hyperterminal or similar: two instances, one for each port
  6. Typing in one window appears in the other, and vice versa.

This worked as expected. However, changing the baud rate completely eludes me. I have tried several things:

  1. Device Manager > COM port settings: When I change the baud rate for one of the devices via device manager, there's no change; the devices still communicate as if they were on the same baud rate; so they must both still be on the default. In other words, it seems to do nothing. I didn't even have to change the baud rate setting in hyperterminal.

  2. Downloading something called the "NON-STANDARD Baud rate configuration device" (see below). However, it seems it's for setting a range of possible baud rates, not for selecting a specific one. (As described in the tool's documentation.)

The next step? Will I have to do some programming to change the baud rate? It seems pretty obsurd! This chip is used in so many USB to serial devices, there must be an easy way of changing the baud rate?

References

Tools including "Non-standard Baud rate" configuration utility (an220sw.zip)

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    \$\begingroup\$ I've also used the CP2102 and had no problems setting the Baud rate using the Device Manager. \$\endgroup\$ – stevenvh Jun 12 '11 at 15:49
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It's funny how writing a question helps one think through a problem more thoroughly. It turns out there were two issues:

  1. Although I'd seen this link before, I realised I had still made the same mistake; I'd tried a much lower baud, rather than much higher baud, than the bridges support, so it would have disregarded my command like in the link. However, changing the baud rates through device manager to sensible (but different) values, they still communicated as if on the same baud rate.

  2. What finally got it to work, was not setting the baud through device manager, but through hyperterminal (or putty as I'm using). It's always the obvious things!

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I didn't read all of your rather long question, but if a device is installed properly as a serial port, then its baud rate should be settable just like any other serial port.

In general, the baud rate should be set by any app that uses the serial port. This is done with the SetCommState call, but of course the user interface varies from app to app.

None of this has anything to do with whether the serial port is built in, connected via USB, or something else.

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