Error -200621 Internal Buffer Overflow on NI DAQ Device

Updated Feb 12, 2020

Reported In

Hardware

  • USB-6366

Issue Details

I get an internal buffer overflow error when using my NI USB-6366. I am trying to use 6 AI (Analog Input) at the maximum rate of 2MS/s and 2 AO (Analog Output) at 2MS/s. The device specifications says 8 channels can be used at 2MS/s.

Solution

The buffer this error refers to is the FIFO located onboard the NI DAQ device. The number of samples that can be held in this buffer is fixed. If samples are not transferred from this buffer to the PC fast enough, samples may be overwritten and the overflow error will occur.

Possible solutions include:
  • Reducing the number of channels.
  • Reducing the number of samples acquired per second. (ie. Sample Rate)
  • Using hardware with higher bandwidth such as a PXI System
  • Using hardware with a larger onboard FIFO. 
  • Programatically change the data transfer mechanism. Choose the fastest data transfer mechanism supported by your hardware and fits your application. 

Additional Information

If other devices are using the USB controller or you are using an external USB hub to connect your DAQ device, you may see an additional limit to the number of channels and rates you're able to acquire at.

This can occur on any NI-DAQ device. Devices are especially susceptible at high channel counts and high sample rates.