Typical USB Transfer Latency


I plan on using 64-bit Ubuntu 12.04 with a XEM6010 board. What typical latencies do people get with the pipe transfers from the FPGA to the host PC? For example, how long does it take to initiate a piped read from the host PC to when the data arrives on the host PC? I’m looking to read 65,536 bytes of data every 15 milliseconds with minimal buffering.

Thank you.


You may be able to achieve that in bursts, but 15ms is a short period of time in a PC environment (non real-time). Therefore, it wouldn’t be uncommon for you to get “stepped on” by the operating system for disk transfers, GUI updates, background tasks, etc.

In other words, it’s definitely not something you would want to depend on. You’ll want to look to QNX or other real-time environments for guarantees.


Thanks for the feedack. Is the FrontPanel API compatible with QNX or other real-time OS’s?

I guess a bare Debian or Ubuntu server install (ie. no GUI and minimal background processes) would still have issues.

Thank you.


We do have support available for QNX, although it hasn’t been built in a while. Please contact sales@opalkelly.com if you’re interested in this.