Yesterday I wrote in a comment that I didn't break much, except a LED and a LED matrix. However, exactly yesterday I think my Uno gave up, since I cannot upload a sketch anymore (timeouts). For the rest the board seems to work still ok.
I have two possible reasons, and would like to know what I can do to prevent this in future. I connected a 415 MHz RF transmitter and receiver to it, which are working.
- To get more power I attached an adapter (12V), TOGETHER with the USB ... I thought always adapter power would be used, but it seems it is not a good idea to have both connected. Is this true?
- The Uno was inside a case (with holes near the output pins). I know this causes some extra heat, but I would guess that adding just an RF receiver/transmitter would not cause the Uno to heat up more than allowed.
Which of these reasons is the possible cause ... or are there any other reasons I didn't think off. Everything worked fine until I plugged in the 12V adapter and it still worked for some time (until I tried to upload a new sketch).