Can not accede baud rate of 115200 with NI9871

[Hazkel]

I have built a very simple project based on compactRio 9063 and 4 pot serial card NI9871.

I have compiled the FPGA file after inserting NI9871 to the project.

When I set baud rate to 115200 - the RT program is working fine.and i am able to handle serial communication with the extended ports.

But when I change baudrate to 230400 I get an Error:

"Property Node (arg 2) in VISA Configure Serial Port (Instr).vi->RT-Main.vi"

The card should support much higher rates.

What is the problem?

[DaSage]

Take a look at this article:

Serial Baud Rates Supported by NI-VISA

http://digital.ni.com/public.nsf/allkb/D37754FFA24F7C3F86256706005B9BE7?OpenDocument

What happens when you change the baud rate to another one of those listed as supported by “some” serial ports, such as 128000? Do you still get the same error?

[Hazkel]

Thnaks for the reply.

Unfortunatly the only Baudrate that did nor result wit h Error were:

9600

19200

38400

57600

115200

The rest resulted in an error.

See atached screenshot.

[DaSage]

It’s interesting that even some of the baud rates on the list of those supported by most serial ports are throwing errors as well. Is hardware down the line restricting what baud rates are acceptable and which are not? I found another article that references the error you are seeing, and touches on this scenario:

http://digital.ni.com/public.nsf/allkb/5D2B2F533CFD001586256EFC00823580?OpenDocument

[Hazkel]

Thanks for the reply.

I am getting the error  even when no device is connected to the NI9871 module.

The only explanation i I can think about is a bug in either one of:

NI-VISA 15.0.0

NI-RIO IO Scan 15.0

NI-Serial 9870 and 9871 Scan Engine Support 15.0.0

Those three program are installed on the cRIO system (9063) and to my understanding may be responsible to the serial communication.

I atavch a list of all programs installed on the system

[DaSage]

In the NI Serial Hardware Specifications and Features Guide I found an interesting equation that relates supported baud rate to maximum baud rate for your NI 9871 module. After performing some preliminary calculations, the equation seems to indicate that the baud rates you are using should be supported (see page 25 of the link below):

http://www.ni.com/pdf/manuals/373170e.pdf

I know a newer version of NI VISA exists, so you might try installing it to see if it resolves the issue (link below):

http://www.ni.com/download/ni-visa-15.5/5846/en/

[Nitsan]

Hi Everyone,

The NI-9871 supports baud rates of up to 3.6M, including non-standart baud rates.

However, these are all supported in FPGA Interface mode. If someone would like to use NI-VISA VIs with this module, the only option is to use Scan Mode.

It is well known that some C-series modules are capables of working at lower rates when used in Scan Mode and it seems that the NI-9871 is no different.

So it seems that the maximum baud rate for the NI-9871 under scan mode is ineed 115.2K.

Nitsan Gonen

Application Engineer