This way I wanted to aks a question regarding my custom designed CM4 breakout board. It is based on the CM4 IO board design specs and it works perfectly, but I have some problems regarding network or power which I can not debug.
- I use the TI TPS23750 PoE+ reference design HPA107 (Link) Which gives 5V @2A
- Because of the component shortages, I choose to use the Abracon ARJM11D7-104-AB-EW2 ethernet port (10/100Mbps with PoE+ support) (Digikey link)
- The differential pairs for ethernet use the same 100R values as used in the CM4 IO board Kicad reference design
- The board copper thickness, layer count etc is exactly the same as the CM4 IO board
Now I have a lot of problems using the network port on my board.
- 100Mbps-FD does not work and causes the network port to flicker very fast. First I thought this was caused by inference.
Possible mistake is that the Ethernet data line differential pairs are to close together, but this was solved by using the 10Mbps-HD software solution - Lowering the NIC speed to 10Mbps-HD in Debian helped 1 board out of 3 to start working on my Unifi PoE switch. The other boards boot perfectly but the network does not come up and the port start flickering very fast. The changed file:
- Adding a Unifi PoE+ injector before every board and using the software adaptation to use 10Mbps-HD works for every board.
Code: Select all
cat /etc/network/interfaces.d/eth0.conf auto eth0 iface eth0 inet dhcp # Always use 10Mbps half duplex! Full duplex was not fixed in IEEE, so unreliable post-up /sbin/ethtool -s eth0 autoneg on advertise 0x01
The most strange thing is that by adding a PoE+ injector before every board makes it function perfectly @10Mbps-HD. This hack makes me think the cause is a power supply error/malfunction.
I really do hope that someone here can help me debug this, because I find this so strange.