For transportation of several high speed serial ports, we want to use a serial over ethernet approach. At a minimum I need to transfer four ports with 512 byte packets that come in every 40 ms at 2 Mbps.
Search for a ready to use (for test at least) device has turned up nothing. Standard devices usually go up to 230 kbps, some to 1 Mbps. Most faster ones are single port only. And it should be a small device, embeddable, logic level is all that is needed. If anyone knows of a usable device...
Since the board that this is on incorparates an ethernet capable controller (LPC4088) that has not that much work to do richt now, I thought it should be possible to add ethernet to it.
For testing I got an LPC4088 demo board with ethernet interface and got LwIP running on it (stand alone, no OS).
Got it working OK to simulate 4 ports sending slow data to 4 TCP ports that can be opened with a PC terminal program.
But when I turn up the data volume and packet rate, it stops working. In some cases stuck in the hard fault handler, in other cases in a timed waiting loop in the LwIP stack.
At this moment it is running fine with 2 ports open and a 512 byte packet every 100 ms on each. When I increase the speed to 50 ms, it stops after a while.
I have no previous experience with LwIP so where to start looking?
- First of all does it sound feasable over a 100 Mbit ethernet connection using TCP?
- What can be tuned in LwIP to improve this? I have already increased PBUF_POOL_SIZE from default 7 to 64 and MEM_SIZE from 12k to 32k