Does the cRIO Ni-9871 Rs-422 module support Non-Standard BaudRate 500kBaud?

[hinewwiner]

Hello.

I was wondering if Ni-9871 can support non-standard baudrate like 500kBaud.  I have been looking for this..but I couldn't find it yet.

Thank you

[Robbob]

Hinewwiner,

yes, the 9871 supports baud rates up to 3.6864 Mbps, as stated in the NI 9871 Operating Instructions and Specifications

Here is a picture of the configuration of the module from the project, as you can see there is an 'Other' option which lets you put a custom rate in.

[Robbob]

Addendum: The rate is based on the maximum rate divided by an integer, so you can't get exactly 500k, but you can get pretty close, as shown by this screenshot.

 

 

Message Edited by Rob_K on 11-20-2008 03:44 PM

[Upgrading]

How can we get it closer to 500k.  This configuration provide 527k which is 5.3% off.  I'm trying to interface SICK LMS221 laser scanner using cRio NI9014 / FPGA NI9116 / RS422 NI9871.  My reading contained errors 65572, 65573, 65574 & 65575 most of the time when using 527k, but no problems with standard baud, i.e., 9.6k & 38.4k.

Could anyone help me on this problem? Having closer 500k baud or using 527k baud to read 500k data.  Thanks a lot.

[Hueter]

The 9871 is designed to be a simple interface to standard serial ports. For your application you are implementing some custom digital protocol then you can using a generic digital module. Unfortunately the 987x modules only supports a limited number of baud rates. This is because this rate is derived from hardware onboard the 9871 which has limited flexibility. If you need non-standard rates like this you can always implement your own protocol on any digital module. You would then have to write the serial data reader and writer yourself, but in a Compact RIO you would be able to use the 40MH base clock to get a rate much closer to 500k (though still not exact). In the end if it needs to be perfectly synced to another device, it would need hardware level synchronization available in FPGA code.

Hunter

[Upgrading]

Thank you very much, Hunter.  I have NI 9403.  Is it fast enough for 500 kbaud? I have tried this DIO module to interface with RS232, but not successful yet.  I will try it again.

-Vasu

[Hueter]

Yes, the 9403 can go much faster than 500k, so you should be fine there. Check out this tutorial: 

Developing Digital Communication Interfaces with LabVIEW FPGA (Part 1)

[Upgrading]

Thank you very much for your confirmation and useful link.