Embedded systems with liquid crystal displays and touchscreens are becoming more and more frequent nowadays. Using graphical user interface is significantly different from the traditional command line interface. Therefore it is reasonable to create an easily portable and modular developing interface: a graphical library which is adapted to the specific attributes of embedded systems. Planning and testing a solution for this task is the main subject of this thesis. Based on the study of software design’s general processes and methods I chose an appropriate model for this development. Features, interfaces and the internal operation of the graphical library were designed and implemented following the steps of the model. Testing a software is one of the most important part of the development. For this purpose two different test environments were built: an application running on a PC which is capable of monitoring internal behavior of the software and an embedded system realized on a digital signal processor. The latter environment was created on Analog Devices’ ADSP-BF527 EZ-KIT Lite evaluation board. Low-level software components of the evaluation kit were also implemeneted in order to test the graphical library. Device drivers of the LCD module and the touchscreen controller were developed and then added to the software enviroment running on the Visual DSP Kernel real-time operating system. As an example a user interface was designed for direction finding applications. This graphical interface handles input actions of the user to change parameters of the data processing by touching the screen and results of the algorithm are also displayed.