[lwip-users] Trouble getting lwIP to respond to ARP on Xilinx Microblaze config (1.4.0)-

[Andrew Silverman]

Please pardon the noob question, but I’m kinda stuck:

 

I have a Microblaze running on a Digilent Nexys 4 board (Artix 7 FPGA, SMC 8720 RMII PHY) and I’m having some pretty serious difficulty getting any of the sample apps provided in their SDK to work properly. I’m using the 1.4.0 distribution of lwIP that’s included in the Xilinx 2014.2 SDK – latest stuff from them, although not 1.4.1 from lwIP.  I have done some poking around the Wiki and am getting my bearings with the lwIP implementation, but I’m not quite there yet.

 

In particular, I’m just trying to run the raw mode echo server app that listens on port 7 which is supposed to echo back anything that comes in on TCP to that port, however I’ve verified with netmon that the board is not responding to any ARP requests from the PC, so it’s pretty much dead in the water.  However the application appears to start normally: On the console I can see the app assigning the static IP address/mask/gateway, and then the startup message from the echo server app appears.

 

When lwIP debugging is enabled, the startup messages from the app are followed by a long stream of pbuf frees of this sort:

“pbuf_free(0x6e01a8c0)

pbuf_free: 0x6e01a8c0 has ref 65535, ending here.”

 

This is interspersed with this message:

“tcp_slowtmr: no active pcbs”

 

And eventually, the pbuf_free messages stop, leaving just the periodic “no active pcbs” message going as the timer fires.

 

I’m not really quite sure whether this behavior points the finger in any particular direction, so I’m also unsure where to go next in the debugging process. I’m also uncertain as to whether the problem is something in the underlying FPGA PHY->MAC implementation that I’ve put together, or whether the pbuf messages indicate that packets of some sort are being recognized and there’s some purely software problem as to why the ARPs aren’t getting handled and responded to.  Incidentally, I also tried turning on the ICMP debugging option, but this causes garbage to get spewed to the console, which doesn’t occur with any of the other debug options.

 

Any pointers of what I might want to look at next would be greatly appreciated.

 

Thanks!

Andy