3

I have designed an unmanaged Ethernet switch, and cameras that are Ethernet-based with a 100 Mbps connection. If I test my cameras with a commercial switch, they work very reliably up to 60°C or so. If I test the same cameras with my switch I lose Ethernet connection at 50°C or so and I can see that they take more time to connect in general even when cold.

I just want to clarify that the connection fails when the cameras get hot, not when the switch gets hot.

There seem to be obviously something wrong with my switch because it is somehow less tolerant to "something" than a commercial switch. I checked my schematics and layout and can't see anything wrong with it, all components are good quality (crystal for example).

Any idea about what could be causing this? What could cause a weak connection in a switch?

My switch has gigabit connections as well as several 10/100 connections. Different magnetics between them, but I see the same behaviour. Here is a capture of the 10/100 magnetics.

enter image description here

I tried removing the TVS, no difference.

When the connection is lost I have no link and cannot ping. The connection starts going on and off, worse and worse with temperature until it eventually is completely lost. After lettings the cameras cool down under 50°C or so it's all good again.

My cameras show this when it starts to fail, eventually the link is completely gone.

    rt3050-esw 10110000.esw: link changed 0x01
[   48.386907] rt3050-esw 10110000.esw: link changed 0x00
[   50.020357] rt3050-esw 10110000.esw: link changed 0x01
[   50.223384] rt3050-esw 10110000.esw: link changed 0x00
[   51.865861] rt3050-esw 10110000.esw: link changed 0x01
[   57.735428] rt3050-esw 10110000.esw: link changed 0x00
[   59.386378] rt3050-esw 10110000.esw: link changed 0x01
[   64.469765] rt3050-esw 10110000.esw: link changed 0x00
[   66.125834] rt3050-esw 10110000.esw: link changed 0x01
[   68.269781] rt3050-esw 10110000.esw: link changed 0x00
Null
  • 7,603
  • 17
  • 36
  • 48
chourizo
  • 31
  • 2
  • 1
    Did you check the temperature specs of all your components? It's possible that some are not rated to operate at 50C or have reduced performance at that temperature. You could also use a heat gun to selectively heat components and try to identify the problem one. – jwh20 Jan 25 '22 at 14:17
  • "I checked my schematics and layout and can't see anything wrong with it, all components are good quality (crystal for example)." - but you've clearly missed something otherwise it would work. Suggest you share some of that here so that others can look for things you've missed. – brhans Jan 25 '22 at 14:23
  • 1
    Please share the schematic. Do you have TVS diodes on the signal lines? Might be a change in a TVS or cap for example. – Ralph Jan 25 '22 at 14:33
  • 1
    I would suggest that you check the pinstrap or register settings around auto negotiation and then also compare the link settings you get with commercial switch and the link settings you get with your custom switch using diagnostic information from your camera device. – crasic Jan 25 '22 at 14:52
  • What exactly is getting lost? Does link auto negotiation work, or is it packet loss? – pjc50 Jan 25 '22 at 14:56
  • Just to be sure: is that TVS really on the connector side of the magnetics? Please post full schematics. – Justme Jan 25 '22 at 16:24
  • The TVSs have been removed. Cannot post full schematics because it's a commercial product. – chourizo Jan 25 '22 at 18:05
  • Are you absolutely sure the magnetics are 100% correct for the chip? – Spehro Pefhany Jan 25 '22 at 18:19
  • what happens if you connect a hot camera with a short cable? ... (100 cm or less) – jsotola Jan 25 '22 at 18:29
  • I am already using very short cables to eliminate any possibility. – chourizo Jan 25 '22 at 20:13
  • Im experiencing exactly the same issue with the same ethernet controller on an Onion Omega2s+ using Mediatek MT7688 SoC. When temperature goes high dmesg output starts showing exactly the same. rt3050-esw goes up and down. When I cool the system down, it starts working. Ethernet link is being lost, which is also visible on the switch. Have you found any explanation? – Michał Maciej Gałuszka Jul 28 '22 at 20:14

0 Answers0