nidaqmx.errors.DaqError: No DMA channels or USB Bulk Endpoints are available

[minghao1211]

I just bought the  USB-6423. and when I try to test the device by running the following example code on Github in VS Code python, I got the error "nidaqmx.errors.DaqError: No DMA channels or USB Bulk Endpoints are available", which I do not quiet understand. Could anyone help me to solve this issue? Much appreciated.

[ZYOng]

According to USB-6423 Specifications, USB-6423 only supports Data Transfers mode of USB Signal Stream or programmed I/O. By default, DMA is used. You must set ci_data_xfer_mech to Programmed I/O (10264) or USB Signal Stream (I don't have the latest DAQmx driver installed to get the enum value. You might want to check with NI Technical Support).

[minghao1211]

Thanks a lot! Is there a way to find the enum values from the driver than contacting the technical support, which I will do if not.

just trying to save time…

[BertMcMahan]

Did you figure this one out? I'm using a USB-6421 and am getting the same error. Setting the data transfer mechanism doesn't fix it (I'm in LabVIEW, not Python, so I know my enum values are right since it's just a constant).

This code worked fine with my 62xx series and 63xx series USB devices, both of which were limited to USB Signal Stream or Programmed I/O. I got no errors with those.

[BertMcMahan]

Update: I fixed my issue by fully updating all of my DAQmx drivers. DAQmx 2024 Q3.1 was the first version to support the USB-6421, but it didn't work in my case. Updating to the latest (2025 Q2 Patch 1) looks to have fixed the problem.

Also, adding the error code 200251 to help future Googler's find this thread.