This document describes the design and implementation sequence of both hardware and firmware components of two microcontroller boards of 8 and 32 bit architectures, which use similar form factor and share common input/output devices and recently developed web-based user interfaces. Both have been applied mainly to educational and research systems in renewable energy. The focus has been on increasing reliability in the hardware aspects and using a set of in-house C language coding rules for new firmware development and legacy code refactoring. Testing of the low-level drivers, and use of automated tools such as Ceedling for higher level module testing is also described.