Arduino Sketches supposedly compiling/uploading but doesn't seem to be working when checking COM ports with Putty

Question

I'm just starting out with the arduino uno and I've got a program previously loaded on which receives information from a bunch of sensors and outputs the received information through serial. So when I connect from COM3 (as on my computer) to the UNO with putty it outputs the sensors readings.

But I'm having an issue now with resetting the UNO with an empty sketch with just

void setup(){}
void loop(){}

when I upload the above it says compiled but when I connect with putty the old program seems to be still active?.

Any idea as to what is going wrong here?

Answer 1

Make sure you close putty before uploading as it will probably block the commication between the IDE and the Arduino.

Also check not just for compilation, but also for uploading. Use the serial from the Arduino IDE during development. The compilation process knows how to kill that, and will do that automatically.