A developer designs, codes, and debugs programs for the microcontroller, a versatile chip used in various applications from robotics to automotive systems. They work with assembly language to control the microcontroller's functionality. The developer also creates and tests the interfaces between the microcontroller and other hardware components. They may design custom modules, device drivers, or routines to optimize the device's performance. Additionally, they troubleshoot and resolve system failures or issues, ensuring the microcontroller operates effectively and meets the specific requirements of the project. They also document their work for future reference and maintenance.