The basic unit is built on the basis of the ARM MCU STM32F103C8, which communicates with the PC using a USB converter that simultaneously provides power. A micro SD card slot is connected directly to the MCU for data storage and retrieval. Furthermore, via a level converter (3.3V from MCU to 5V) on the I2C bus, the RTC module and three 8-bit gate modules PCF8574. One gate is used to control the 8 LEDs on the front panel and the other two are connected to the LPT expansion connector. The front panel therefore contains 8 LEDs, an expansion LPT connector, a RESET button and a switch for programming (MCU requires it)