Mikroe MCU CARD 13 for STM32 STM32L152ZD allows for installation and replacement of the microcontroller unit (MCU) on a development board equipped with an MCU Card socket. The new MCU Card standard ensures compatibility between the development board and MCUs, regardless of pin number and compatibility. MCU Cards are equipped with two 168-pin mezzanine connectors. This allows them to support MCUs with an extremely high pin count. The design allows for usage with the plug & play concept of the Click board™ line.