global net_impl.cpp:178 setUpNet DNN module was not built with CUDA

[renatocsanchez]

on Jetson Nano 4gb
After running the script (without errors), it still reports 'no CUDA:

[ WARN:0@9.371] global net_impl.cpp:178 setUpNet DNN module was not built with CUDA backend; switching to CPU

[Qengineering]

Your issue seems to originate from a too low CUDA architectural number (arch).

Before diving into the OpenCV code to see if there is a fix possible, would you be so kind to reinstall OpenCV without the
-D CUDA_ARCH_BIN=${ARCH}
-D CUDA_ARCH_PTX=${PTX}
lines in the script.
Now, it will use arch without (in our case) a limiting number.

see also: opencv/opencv#15858