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:
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.
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.
The W5500 runs at 25MHz and the circuit design follows the recommendations provided by WIZNET.
The application firmware doesn’t generate much network traffic. Most of time it is sending MQTT Keep Alive message once every 30-seconds.
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.