Arduino Sainsmart uno communication problem I'm trying to communicate with my arduino uno but it seems to have troubles to understand characters. For example, printing things with Serial display weird things, changes characters, removes some. 

For exemple printing "test !" every two seconds results in that : 



Every characters have been removed except "!"...

Is my arduino broken ?  Thanks in advance
You are doing 2 things wrong in your program:

First is using serial.write(), which writes bytes rather than ASCII.

Second is you are declaring a string literal as a char instead, you must declare a string using  double quotation marks (which is ") so that your program should read:

Serial.print("Test!");


When you declare 'Test !'  you are doing it wrong, and it will only take the last char in the string, which is '!' - using single quote marks is for a single char declaration, like '!' or 'T', and you can make an array of chars into a string if you wanted, like this:

char array[] = {'T', 'E', 'S', 'T', '!' };
Serial.write(array, 5);


but why would you when the earlier one works better?