Hey!

Time to go on with this... Ok.

Modularity is key in these kind of projects. I don't want to spend ours and ours routing a big PCB and then realize a small piece is wrong. That's not for me.

So, the idea here is to create small parts that we can certify they work independently. As the motherboard depends on two big components, let's make the modules according to that:

• Switch from one side
• Compute modules for the other

The first point is to make the switch work with no problems. We can reduce the size of the prototype's PCB drastically if we create an independent switch board. Once we have that we can test it and then make the Compute modules connections to the main switch board. We have to be careful with the connectors we use there because they can corrupt the Ethernet signals and screw up the whole thing.

From the side of the compute modules... It'd be nice to have the chance to connect other kind of compute modules, but we can't expect all of them to have the same DDR2 pinout. We'll stick to the Raspberry Pi CM3 one at the beginning but it looks like we should make something to change this. One of the options is to keep the motherboard separated in the two parts so we can use the same Switch board with different Compute Module boards. The compute module board must have all the necessary connections for the Compute Modules to work and expose the necessary pins: all the Ethernet connections, and the power source connection...

So, the first point is to make the Switch work 100%, and then go expanding PCB with the other module. We can insert the switch in a PCB that is soldered later on the final one, like the  RN4020 does. With that design, we can even distribute the Switch board independently for others to use it in their projects, and then go on with the CM part.

I don't know, we have to start somewhere, don't we?