PCIe serial board (8430/8431 etc) latency??

[iamsskim]

Hi,

I'm considering using serial boards. Let's say I'm using 4 port PCIe 8430 board. Now, I'm sending 600bytes to each port at the same time. How much latency should I expect? Further, how often can I send those data for each port? 100hz? 200hz? (600bytes for each channel at 200hz means, 120,000bytes per channel per second + 200 times of Windows COM port access overhead per second. Is this achievable?)

Thank you.

SS

[Simon-P]

Greetings;

While a command such as VISA Write takes about 2ms to execute, there might be a delay between commands simply because of how windows functions.

The PCI-8430 can be set for flexible and nonstandard baud rates from 57 to 1000 000 baud and thus offers data transmissions between 57 bit/s to 1 Mbit/s, which, I believe is for the whole device. Still, I’m unsure and will double-check.

Cordially, 

Simon Perez

Applications Engineer

National Instruments

[iamsskim]

Thank you for your reply.

It is too bad that the execution time is very long.

2ms is actually not so great. It means I can communicate only 500 times per second.

I'm not sure if it is inherent problem of Windows OS.

Unlike serial communication boards, I can execute read/write of an instataeous value from/to Ni-Daq boards in less than 500um even with Matlab daqtoolbox. I assume that if I use NI API for Ni Daq, that could be even shorter. I kind of wished that level of speed. (I'm not talking about baud rate, but the rate of communication event. Baud rate of 1M is not bad for RS-232.)

Anyway, I think I'll have to research a bit more to find the best solution for me.

One more question. Is there any way to override/bypass Windows so that my software can use the NI serial board directly? 

Thank you.

SS

[Simon-P]

Greetings;

Indeed, latency like that is inherent to Windows as well as most general purpose OS's. Another option is to look into a Real Time OS which might be of aid in reducing that. 

About your other question, to my knowledge, there is no way to bypass Windows to do that.

Cordially,

[iamsskim]

Thank you for your clarification.

Have a nice day.