Pushing max baud rates on cRIO-9045

[CaseyH_UI]

Hi all,

I'm assembling a headless data acquisition system for a range of mixed signals (RS232, CAN bus, AI, DI). I have an inertial navigation system that transmits at very high baud rates (up to 2Mbaud).

I wrote a simple serial polling VI that streams the raw binary data to disk and is able to keep up with the 2Mbaud rate with no issue. I tested it on my windows PC, using an FTDI USB/RS-232 adapter through NI-VISA. Works fine.

Moving to the cRIO, I see that the RS-232 port on the 9045 supports up to 115.2k. I also see that the FTDI device shows up in MAX if I plug it into the USB 2 port on the cRIO chassis. However, it's still limiting my max baud rate to 115.2k. Anything higher, and NI-VISA throws an error stating that the "configuration value is not allowed" (or something like that).

Can I get around that 115.2k ceiling? I can get away with cutting my baud rate to 1M, but not lower than that. I know the FTDI device isn't the bottleneck, as it functions on my PC without issue. Is it possible that I need to install a specific linux driver to utilize the higher speed?

[CaseyH_UI · Accepted solution]

In case others have the same question - the solution ended up being fairly obvious. The FTDI driver on Windows is tolerant of non-standard baud rates. The driver that comes bundled into the Linux kernel is not. I was able to get higher baud rates on my RT target by sticking to the "standard" baud rates of 7.3728 Mbaud/(2^n).

It still refuses to let me set rates above 1Mbaud (which is also odd), but it accepts 921.6K, which is close enough.