You can feel it heat up within 30 sec and the trace flatlines after a few minutes (i.e. data isn’t being sent anymore).
I am going to run the same code on the other dev board and see if I see the same thing. Should tell us if its the chip or the software, although your example suggests its the hardware in this case.
Update: I ran your code and mine on the SC20100 board and don’t seem to have any problems. There must be something wrong with my SC20260D module.
Please toggle bot UART pins and check on the scope. Do they swing all the way 0V to 3.3V? I am curious if there is a short.
Do you see this on other COM ports or just the one?
Okay, I think we got this figured out. I had 2 issues going on. 1.) The scope probe I was using is flaky, so the waveform never stopped outputting, I just stopped seeing it. 2.) The processor does warm up a bit under load, but nothing too crazy (once you measure it). I have a Thermistor that plots temp of a component on my system. I temporarily repurposed it to look at the processor. I ran a pin toggle test (and yes, they swing to 3.3). Here is the plot:
All the way to the left is the ambient temp. The first bump up is placing the thermistor on the processor body while it is plugged in to USB with no program flashed. The next bump up in temp is after flashing a program with the debugger attached. So, nothing crazy. I think that flaky probe put me on high alert, looks like all it good.
You almost gave me a heart attack, thanks