We have an AWS IoT based device using the W5500 chip. The device works flawlessly when it connects directly to a router or a switch. However, it seems to be locking up if it is plugged into a wall jack in a large commercial building. Here are some of our observations:
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My company has several buildings and each has its own network segment. If this device is plugged into a wall jack in a relatively small building, typical IP 10.66.xxx.xxx, we do see disconnect events at the AWS IoT application layer. However, the device can recover/reconnect without a problem.
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If the device is plugged into a wall jack in the large multi-story office building, typical IP 10.68.xxx.xxx, it appears to lock up from time to time. When this problem happens:
- There is no traffic coming out of W5500 when we put a network sniffer (TAP) on.
- The ICMP ping gets no response.
- We can still read/write all internal registers.
- We monitor the SIP register in case there is a reset on the W5500 side, but we haven’t seen one.
- Again, if we install a LAN switch between the device and the wall jack, the problem seems to go away.
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The W5500 runs at 25MHz and the circuit design follows the recommendations provided by WIZNET.
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The application firmware doesn’t generate much network traffic. Most of time it is sending MQTT Keep Alive message once every 30-seconds.
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Not sure if this matters - In the firmware we set to use 10BT Half-duplex with auto-negotiation disabled even though PMODE 0-2 pins are all pulled high.
Any thoughts? Thanks.