Buffer Error -201025 or -200462 in Output Task

Updated Jan 10, 2023

Reported In


  • Multifunction I/O Device


  • LabVIEW


  • NI-DAQmx

Issue Details

I have my USB DAQ device set up for a hardware timed output task, when I run my program the DAQmx Start Task function I receive: 

Error -201025 
Non-buffered hardware-timed operations are not supported for this device and Channel Type. 


Error -200462 Generation cannot be started because the output buffer is empty.


If you are trying to run a task in hardware-timed single point mode, first make sure your device supports this mode . The most common cause of Error -201025 and Error -200462 is a failure to load the buffer before starting the task. Doing so creates a non-buffered, hardware timed task, which is not supported by USB DAQ devices due to the inherent latency of the USB bus. 

Without calling the DAQmx Write before the DAQmx Start function, your device will attempt to pull samples from a buffer that does not exist. You can eliminate the error by calling a DAQmx Write before the DAQmx Start function.

An example of this can be found in the LabVIEW example, Voltage - Finite Output.vi  found at
Help » Find Examples » Browse » Hardware Input and Output » DAQmx » Analog Output 


Additional Information

If you now get error -200802 due to a zero output buffer size, increase the amount of data that you are writing to the buffer to increase its size. 

This image is a LabVIEW snippet, which includes LabVIEW code that you can reuse in your project.  To use a snippet, right-click the image, save it to your computer, and drag the file onto your LabVIEW block diagram.

This code outputs 0V and 3V to AO0 and AO1 respectively. In order to eliminate error -200802, two samples of data are written per channel