Hey!
I've got an issue with CM4 linking with ethernet switch KSZ8795CLXCC. I've got 2 CM4, I/O board and custom PCB with KSZ8795CLXCC. The connection with the switch is transformerless through 100nF capacitors. The traces were designed to have proper impedance and length. One of the CM4 works with no problem. I can connect my PC to the switch and ping this CM4 with a success. It manages to connect with the switch:
[ 17.214026] IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
[ 17.214427] bcmgenet fd580000.ethernet eth0: Link is Up - 100Mbps/Full - flow control rx/tx
However, the second CM4 doesn't work. After power up, the link stays down. When I connect it to the I/O board and connect with my PC directly to it via ethernet cable, it doesn't work neither - I can't ping it. Unless I connect it through USB-ethernet adapter. Then it can establish 1Gb connection and I can ping it with my PC. Both CM4 have exactly the same image loaded with the same config. The thing is, some weeks ago both modules worked fine. I just want to know, what caused the malfunctioning. I measured TX and RX lines with both modules. The working one immediately started communicating with the switch with proper frames - 100Mb, ~2.2Vpp. The broken one, while receiving such frames from the switch, kept replying with frames of ~3.8Vpp. Also, when I connected with the broken one through UCB-ethernet adapter and forced 100Mb communication, it turned out that the module is able to send proper frames with voltage ~2.2Vpp. I'm wandering, what is causing the problem with the switch?
There is no schematic of CM4 nor datasheets in the internet of the ICs used, so I can't even check the voltages or anything on the CM4 PCB. Would be glad for any ideas.
I've got an issue with CM4 linking with ethernet switch KSZ8795CLXCC. I've got 2 CM4, I/O board and custom PCB with KSZ8795CLXCC. The connection with the switch is transformerless through 100nF capacitors. The traces were designed to have proper impedance and length. One of the CM4 works with no problem. I can connect my PC to the switch and ping this CM4 with a success. It manages to connect with the switch:
[ 17.214026] IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
[ 17.214427] bcmgenet fd580000.ethernet eth0: Link is Up - 100Mbps/Full - flow control rx/tx
However, the second CM4 doesn't work. After power up, the link stays down. When I connect it to the I/O board and connect with my PC directly to it via ethernet cable, it doesn't work neither - I can't ping it. Unless I connect it through USB-ethernet adapter. Then it can establish 1Gb connection and I can ping it with my PC. Both CM4 have exactly the same image loaded with the same config. The thing is, some weeks ago both modules worked fine. I just want to know, what caused the malfunctioning. I measured TX and RX lines with both modules. The working one immediately started communicating with the switch with proper frames - 100Mb, ~2.2Vpp. The broken one, while receiving such frames from the switch, kept replying with frames of ~3.8Vpp. Also, when I connected with the broken one through UCB-ethernet adapter and forced 100Mb communication, it turned out that the module is able to send proper frames with voltage ~2.2Vpp. I'm wandering, what is causing the problem with the switch?
There is no schematic of CM4 nor datasheets in the internet of the ICs used, so I can't even check the voltages or anything on the CM4 PCB. Would be glad for any ideas.
Statistics: Posted by Gorezu — Tue Jul 30, 2024 12:40 pm — Replies 1 — Views 38