How can I create a 6 port ethernet switch with BotBlox hardware?

– Copied from a customer query –

I am looking for the Ethernet switch port. Do you have option for 6 ports?
I don’t need PoE. I’m interested in BB-GGN-A-1
Do I need to worry about common-mode voltage and do I need capacitors?

If you only need 10/100Mbps ethernet, then you have a few options

Option 1: Chain two BB-SWB-E-1 together using a four pin molex picoblade cable. This would use up a port on each board, and the connection between the two ports would be a bottleneck, but it would leave you with 8 available ports. The advantage of this approach is that it is cheap. The disadvantage is the bottleneck between both boards.

Option 2: Stack two BB-SWR-G-1 back to back to form a 10 port switch. This would not consume a port on each, and also would not result in a bottleneck, but it is more expensive.

If you need 1Gbps ethernet, then you have a few similar options.

Option 1: Use a BB-UBS-B-1 + BB-UD1-B-1. This would give you 8 x 1Gbps ethernet ports. Note that these ports can also run at 10/100Mbps. This approach is the simplest but it is more expensive.

Option 2: Connect two BB-GGB-C-1 together using an 8 way Molex Picoblade cable. This would use up a port on each board and leave you with 8 ports; as before the port connection between each board would be a bottleneck. This approach is cheap but as mentioned, uses a port on each. (You could do the same with BB-GGR-C-1).

With respect to your second question. All our boards contain transformers, apart from BB-GGN-A-1. If you are using BB-GGN-A-1 with your own baseboard design, then yes you need to consider whether the downstream devices need transformers.

BB-GGN-A-1 contains series capacitors already, so you can connect it to any voltage mode PHY. If you are connecting it to a current mode PHY, then you’ll need to ensure there is a transformer on that PHY. Most devices that use current mode PHYs also contain transformers on their end, which would work with BB-GGN-A-1. Below is a link that contains some useful information regarding the difference between a current and voltage mode PHY.