When looking that the text in the description, it says Transmit. Does this mean Transmit from the Switch ie Data out of the switch. Can you clarify pls? Thanks
TX is output from the switch. Connect this to the RX of your other device.
RX is input to the switch. Connect this to the TX of your other device.
Here is an example of a tested design to connect this port to 1G PHY over SGMII.
Unless I’m misunderstanding one of the other reference schematics ( UbiSwitch-DaughterBoard-Designs/UbiSwitch DaughterBoard/Schematic UbiSwitch DaugterBoard.pdf at main · botblox/UbiSwitch-DaughterBoard-Designs · GitHub) the opposite directionality is implied. Is this one actually incorrect?
Thank you!
Yes, I can see the confusion.
The port labels on the UbiSwitch baseboard show input and output and that conflicts with the information given here.
This snippet from the UbiSwitch Baseboard schematic, showing the SFP card edge, seems to imply that RX is an input to the SFP card edge, while TX is an output from the SFP card edge. By that same logic, that would imply that RX is an output from the Switch, and TX is an input to the switch. This is not correct, the direction of the ports on this schematic should be ignored.
The nets labelled “RX” on this schematic are inputs to the switch. While nets labelled “TX” on this schematic are outputs from the switch.
To further corroborate this, let’s take a look at the example schematic using UbiSwitch with DP83867, which has been tested.
Note that P0TX connects to pins 28, 27 on the DP83867
Note that P0TX connects to pins 35, 36 on the DP83867
From the DP83867 datasheet.
Pins 27 and 28 are inputs on this chip, which connect to P0TX. Thus P0TX is an output from UbiSwitch, and P0RX are inputs to UbiSwitch.
Appreciate the clarification on this! If I could suggest a future addition to the UbiSwitch datasheet, showing functionality directionality (like the DP83867 snippet you showed) would hopefully clear this up for others in the future.
That’s a damn good idea, thank you for the suggestion, we’ll make the change to the datasheet.