125000 baud

[TheFox]

I am using LabView 7 and am trying to talk to some external hardware which needs the baud rate set at 125000.

When I use the VISA serial with a baud rate of 125000 I get "Error -1073807330 occurred at Property Node (arg 2) in VISA Configure Serial Port"

How can I set a baud rate of 125000.

Many Thanks

[Chris_Rake]

125000 baud is a nonstandard baudrate and is not available from standard COM ports. For most hardware the closest baud rate is 115200 which is 8.5% off (as a rule the two sides need to be within about 4% for successful communication to occur).

Currently the method to get exotic baud rates with NI serial interface cards is to replace the oscillator. In your case if you replaced the 7.3728MHz oscillator with a 8MHz oscillator you would get a baudrate of 125000 instead of 115200.

[Chris_Rake]

Update!

The NI-843x High-Performance serial interface cards are now available. They will allow for custom baud rates from 57 bps up to 1 mBit/sec to within 1% WITHOUT changing the oscillator! So if you want 125,000 baud, the 843x hardware will deliver! For more info on the NI-843x hardware, you can check out the product page at http://sine.ni.com/apps/we/nioc.vp?cid=13692〈=US

[Rich_McGlynn]

Chris,
Great info. Do you know if there are any instruments that provide an "adjustable baud rate"? Something other than the NI rs485 PCI card that is predetermined by the oscillator.

Thanks
Rich Mc

[wiltdavi]

I am using LabVIEW 8.6 and I am having the same issue, when using the VISA serial VI to control a USB to Serial port it will not allow me to control the serial port at 125000.  This same port can be controled by a generic com port controller at 125000.

The error I am receiving is "Error -1073807330 occurred at Property Node (arg 2) in VISA Configure Serial Port"

This thread explains that there is hardware that can run at 125000 so I have to believe there is a way to control a serial port at this baud rate also.

Hopefully somethine can help me with this.

Thanks.

[GPIB_Guru]

I think this thread is dicussing a special serial port hardware that is capable of 125k. Most serial port hardware is incapable of that baud rate.

[JasonSmith]

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wiltdavi wrote:

I am using LabVIEW 8.6 and I am having the same issue, when using the VISA serial VI to control a USB to Serial port it will not allow me to control the serial port at 125000.  This same port can be controled by a generic com port controller at 125000.

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When you say generic com port controller, are you referring to a built-in COM port on a computer, or a third-party PCI, USB, or some other type of serial interface? The error you are receiving indicates that the driver has rejected the 125000 baud rate. Some serial drivers will reject baud rates that they know the hardware can attain (NI-Serial typically works this way), while other serial ports will just select the closest baud rate--no matter how far off it is from what you specified.

If the port this works with is a built-in serial port on a computer (Or many add-on adapters), then it is probably actually running at 115200, and not the 125000 you specified. If this is the case, you should try just setting your USB Serial adapter to 115200 to see if it will communicate. Different add-on serial ports will have different oscillators and clock dividing mechanisms, so how close they can get to the baud rate you specify is very hardware dependent. I am not sure from your original post if your USB serial port adapter is an NI model, but I have confirmed that our NI USB-232 controllers will be unable to attain 125000 baud. The closes attainable baud rate is 115200, which exceeds the error threshold used by our NI-Serial driver,which will result in the error you received from VISA.

-Jason S.

[wiltdavi]

Thank you for you response.

As it was brought to my attention that this was a HW thread, I have started a new thread for the software side of the question.  It can be found at: http://forums.ni.com/ni/board/message?board.id=170&message.id=429139&jump=true

I have added more information to that thread to answer your questions about what I am trying to do.

Thanks again.