2 Dec 2021

   I updated the schematic to utilize an 8 pin Micro Mate-N-Lok for the power input, using 4 pins for the 5V supply, three GND, and one 12V.

   The height of the Mate-N-Lok connector is 8.67 mm ( 0.342" ).  The PC104 spacers ( distance between board surfaces ) are 15.24 mm,  ( 0.600 " ),  so it looks OK to use.

   I'm very happy you mentioned stack height !  The Bot Blox Gigabit part has a height of 15.98 mm ( 0.629" ), which will not fit into a standard PC104 stack.

   The Bot Blox 10/100 has a height of 11.30 mm ( 0.448" ).  So it seems the 10/100 would be the best choice for this application.

   Therefore, I changed the Bot Blox PC104 Picoblade connectors to the 4 pin version, and the Harwin connectors to the 4 pin right angle version.

   Jumpers. 

      If we utilize the jumper - header scheme, wouldn't we need 5 of them , one for each port ? 

      Looking at the Bot Blox 10/100 bottom side, it's not immediately obvious how to connect to the contact points for the ethernet Picoblade jacks.  So it seems we would need to use Picoblade plugs to connect from the Bot Blox to the PC104.

      Therefore, it's my opinion that we should use individual harnesses from the Picoblade jacks on the Bot Blox directly to Picoblade jacks on the PC104 for either Harwin or RJ45.

      What are your thoughts ?

1 Dec 2021

I would suggest using at least two pins for 5V, the whole PC104 stack might actually use 5A. Are you running out of stack height with a double row connector?

The current power supply PC104 board has two wires for GND and 5V and it has an additional thin wire pair for 5V/GND (not sure what this is for).


Another thing to think about is how do we jumper which ports to use (the Harwin or the RJ45). Having a harness for each might be messy because we have to squeeze all of it between two boards in the stack. Maybe we can see if there are multi-pin jumpers like this we can use: https://www.digikey.com/en/products/detail/amphenol-icc-fci/69145-216LF/1528654

If we put a 3x8pin header on the board you can decide which way to go without being able to use both sides at the same time.

What do you think?

Erik