Decided to make a simpler prototype of the Digital I/O Board : 

Instead of having the intended STM32(F205) based board featuring nice things as : 

• Onboard test programs
  • Sporting fixed timed sequences
  • Patterns
• Connecting to the SPI bus using over-engineered addressing decoder functionality

The board now connects directly to I2C bus but still features the desired functionality : 

• 2 x 8 bit ports which can be either input or output
• 1 x 8 open switches (Opto Couplers)
• All connectors aligned with the connectors on the Raspberry Pi for easy front plate design.