Stratix Router Development (4/17)

4/17 - The PHY error was fixed, but still DHCP was unable to be sent/received. The LED light on the board was lit, however. This may not seem like a big issue, since DHCP is low priority for the board's overall function as a router, but the DHCP packets failing to send are a symptom of the issue that the board is still unable to send/receive packets. After investigating the method for packet sending, I added a print statement for debugging purposes. The board sends by setting up a send-queue and by running through it and sending packets as it goes along; it is this that I sought to debug. Printing out the contents of the send queue each time it was added gave us two pieces of information:

• The contents of the send queue were identical each time something was added into it.
• The timing of the sends was apparent. Data was added to the send queue (and the print statement was therefore triggered) every few seconds after the board detects an Ethernet link (and the LED therefore turns on).

Wireshark (a packet monitoring software) determined that no data was being actually sent out of the port, not even garbage data. I used an oscilloscope to probe the live pins to confirm this. There is no signal on any of the Tx or Rx pins of the Ethernet cable, even though the LED is lit and the print statement is being triggered, informing us that the send queue is being used. It is still unclear how to solve the problem of packet sending/receiving, but we have learned more about the situation.