I am having Ethernet troubles. I made a PCB that has Ethernet. It pretty much mirrors what is on the stm32 nucleo boards, with the exception that it uses a magjack. When I plug in a standard Ethernet cable, it works fine. When I try a flat one, it does not work and I cannot communicate. I plug the flat cable into a computer to a router or something, it works fine, though. Is there something specific to flat Ethernet cables that make it different?

 

The main difference is that in in round cables the pairs are twisted. In flat cables they are not twisted leaving them susceptible to EMI interference and crosstalk. Flat ethernet cables do not meet the same standards as their round counterparts.

 

You are sure one of them is not An Ethernet crossover cable? Take a look at the differences in the link. Also see the above post for difference between round and flat.

Ron

 

I am having Ethernet troubles. I made a PCB that has Ethernet. It pretty much mirrors what is on the stm32 nucleo boards, with the exception that it uses a magjack. When I plug in a standard Ethernet cable, it works fine. When I try a flat one, it does not work and I cannot communicate. I plug the flat cable into a computer to a router or something, it works fine, though. Is there something specific to flat Ethernet cables that make it different?

What type of mag jack is it? Part number?

 

Found the issue....I accidently shorted the chassis ground of the connector to the actual ground reference of the circuit. Took the short away, boom, worked.

 

Yay!

Ron