Hi, I am making a GUI to control robot by sending serial output. My ideal is write a program that continuous send serial string, and when press a button, one character in that string will change. For example: my output is 'aaaa', when press 'change_first_char_button', my output will change into 'zaaa', and when release that button, the output will return 'aaaa' . The output will depend on what button is pressed.So if press 'change_first_char_button' and 'change_last_char_button', the output will be something like 'zaar' I know it sound simple but, I still cannot figure out how to make it. Thanks.