This diploma paper introduces development and implementation of access control system. It is made of STM32F4 microcontroller based on ARM Cortex-M4 processor, TFT touch screen, RFID card reader and RS232/TCP converter module. Part of the system are also two programms which are running outside of the controller. First, the server side program is used to check RFID tags and belonging PINs, the second one does the logging. Beside logging, its functionality is also adding or removing users from the database. Operating system we are using on microcontroller is FreeRTOS, one of the free versions of real time operating systems. We used programming language C for coding the microcontroller and programming language Java in combination with C# for the rest.