RS-422 64K baud rate possible?

[jblaschk]

Hi, I have just received a project to develop software for a data acquisition system that will receive async serial data over an RS-422 port at 64kbps. I am pretty familiar with serial ports and writing software for them, but only at the standard PC baud rates (9600, 19200, 38400, 57600, etc). I was planning to use the SerialPort Class in .NET C#, but when I try to open a COM1 port on my PC using that baud rate I get an exception "The parameter is incorrect".

Help Jan? Am I going to have to write a custom software UART using an 8052 microcontroller, or do some other type of low level coding to be able to handle this non-standard baud rate?

Thanks

[Jan Axelson]

The serial-port hardware only supports specific baud rates. I would ask if the data acq system could instead use 57600 or 115200.

If the PC uses an FT232R or similar USB/serial adapter, you can set non-standard baud rates.

[HDowns]

If this is an external RS-232 - RS-422 converter then the answer - usually, no.
If this is an internal RS-422 PCI board or USB converter then the answer - usually, yes.

[jblaschk]

Thanks Jan and HDowns for the replies. I found a USB-RS422 serial converter that uses the FTDI FT232R chip that allows non-standard baud rates that should do the job nicely. Thanks for that suggestion. I will let you know how well the driver works with C# calls after I get it.