For non-embedded programmers the first thing to try on a new system or in a new programming language is to print out "hello world". The equivalent for microcontrollers and other embedded systems is to blink a LED. When even the target circuit and the programmer are freshly put together it is wise to start even lower, with a blink-a-LED program written by someone else that is known to be working. Then when the LED does not blink (which is likely) there is one thing less to doubt about. On this page you will find 1 and 2 Hz blink-a-LED (and some other) test programs for various targets chips and circuits. Two blink frequencies are provided so you can check whether a target that already contains one of the blink programs is realy reprogrammed by using the other one.