No debug output when video is output to screen

[jdelange]

I raised this as part of another issue, but I thought this might be suitable for a separate issue:

Problem: I try to get debug output, however, as soon as there is an image on the screen, the debug output is interrupted. I assume the resources of the Pico are overloaded? Is there a way to fix this?

Running on Pico2

[scrapcomputing]

Unfortunately I don't think there is a good way around it. Printing to the debug output consumes enough resources that destabilizes the video. A workaround that kind of works is to print output once every N frames. It will most probably still generate some regular artifacts but at least you can tell that the artifacts are caused by your debug output.

[jdelange]

It's not destabilising the video. The video just carries on, there is just no debug output anymore. So we can print debug to a console or file, but we never get to see it, because the system is too busy with the video stream. So what's the use of debug? It only works when there is no video out at all?

[jdelange]

Ok, I found the problem. Apparently the power supplied to the Pico via the USB connection is insufficient to power both the video out and the debug. I assume the voltage drops to a level too low for the Pico to reliably run and create output to the debug console, or the development PC USB port is overloaded and this cuts the debug logging.

If I hook up a second power supply (with a schottky diode inserted to prevent back flow), then I can have video output and debug logging at the same time.

[scrapcomputing]

I doubt that the USB power is the issue. The pico consumes just a few milliamps, way less than the USB limit. Could it be some issue with your USB cable?

[jdelange]

Hi, the dac resistors in the VGA out do take some milli amps too. The USB connection otherwise works fine.