I maked custom board based on RPi CM4. ETH connector is on top of PCB and SOM is on bottom side, so I decided to swap pairs to make track routing easier . BCM54210 datasheet is not available, but CM4 datasheet specified that PHY can detect pair swap and line swap. First prototype have ETH pairs swapped as follows:
CM4 - RJ45 socket
TRD0 - TRD2
TRD1 - TRD3
TRD2 - TRD0
TRD3 - TRD1
Ethernet doesn't work on straight cable, but when I swapped pairs in RJ45 jack to reverse changes on PCB it works fine.
Is there any limitation regarding to pair swap or maybe I made something wrong? What about polarity swap in single pair?
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