When working with the W5500 Module, you can use either the PicoConn or RJConn daughterboards with GigaBlox Nano. In both cases, connect one of the GigaBlox Nano ports directly to the RJ-45 port on the CH9121 module and the connection will come up.
W5500 uses a current based PHY on its ethernet port. Diagrams for typical current based PHY and voltage based PHY are shown below.
A typical current mode PHY ethernet system
A typical voltage mode PHY ethernet system
As evident from the diagrams above, a current mode PHY relies on the use of an external transformer to generate the ethernet voltage signals. Essentially, the current mode PHY pushes and pulls current through the transformer, which in term pushes and pulls current to/from the 2.5V rail connected to the center tap of the transformer.
This alternative current flow generates an alternating magnetic field in the transformer that induces an alternating voltage on the other side of the transformer.
Thus, a current mode PHY requires a transformer to generate the necessary ethernet signal. This is in contrast to a voltage mode PHY which already generates the necessary ethernet voltages. A transformer is not required for operation in a voltage mode PHY.
The PHYs inside GigaBlox Nano are Voltage Mode, which is why GigaBlox Nano can be used without transformers. Using GigaBlox Nano with another voltage PHY is simple, you can either use transformers or omit them. GigaBlox Nano contains capacitors in series with the ethernet lines meaning that another Voltage Mode PHY can be directly connected with GigaBlox Nano.
To use GigaBlox Nano with a Current Mode PHY, you will need to connect a transformer to the Current Mode PHY first, with the center tap of that transformer connected to a 2.5V rail. Unfortunately this means that a Current Mode PHY can never be truly transformerless.
The table below shows the pin mapping between the W5500 and GigaBlox Nano
|W5500 pin name
|W5500 pin number
|Transformer with 2.5V center tap
|Transformer with center tap AC coupled to ground
|GigaBlox Nano Connection Name
|GigaBlox Nano Pin example for Port 0
GigaBlox Nano pinout