It was several years ago that I dropped some questions here, and out of courtesy for the help received I thought I might give an update where I am right now.
I was able to get the hardware and put it all together.
In addition to the MBHP_CORE_STM32F4 mainboard it now consist of MBHP_MIDI_IO, a DIN and a DOUT module. I connected it together and did some basic hardwaretesting and everything seems to be OK.
Next step will be building the hardware controls. It will have 8 SSD1306 based OLED screens. each with a clickable encoder. In addition two RGB clickable encoders positioned to the right of the 8 screens and encoders. As my intention is to build only one, I will use two sided veroboards, that I will adapt to size to match the case.
It wil then be but into a tilted box. It depends how good it will look after putting the holes. If it is still OK after drilling and sawing I will leave it as is, otherwise it will be painted PPG blue.
And I still have three options for the knobs.
It will be my midi utility box with several modes: basic midi controller, converter between my hardware Mackie C4 and several synths and ... whatever I will need in the future.
It will be base on the Midibox NG software.