Posted on May 17, 2011 at 09:31Hi Guys,
Most of the examples I found knocking around were based around 0.9 of the uIP, not 1.0, so I decided to do a new port. A few things found on my travels:
1. The implementation of the timer routine that uIP needs (use by ARP etc.) didn't work properly in most examples and result caused connections to get cleared out too quickly, or the timer poll to UIP was thrashing the system.
2. The ENET driver supplied with the HAL only has a 1 deep DMA rx buffer and it's also polled by the app. This can result in two packets that get received in a short period of time to get corrupted. The knock on affect is your browser waiting for about 6 seconds before it re-tries. I ended up writing my own one based on a combination of the Keil ENET driver and a few principles from the ST one.
3. The throughput on uIP is really bad out of the box (limited to about 6KBytes/Sec). This is because it can only process one packet at a time and Windows implements delay Acks. The delay ack means that it will only ack a packet if 200ms has passed, or it's received another similar segment packet from the server. This means those 200ms soon add up and hence 1.5K * 5 = approx 6K/Sec... far lower rates if sent tcpip packets are not full. The Keil HTTP server demo that uses their IP stack doesn't have this problem, but you have to pay good $$$$ for that!
4. A few byte packing issues on structures.
5. For good performance I rewrote the CRC and 32 bit routines to be 32bit ARM native.
6. Proto-threads as used by the uIP http demo is a complete nightmare to debug. On the surface a cool concept, in practise it's virtually impossible to trace through.
After lots of hard work I've now got the uIP webpages appearing virtually instantly, rather than not displaying for about 5-10seconds (as seen on the dynamically generated script based ones).
If I was doing this again I would actually consider buying the Keil IP stack, as I must of spent a few thousand dollars worth in time getting uIP and Ethernet drivers working properly.
Sorry, can't post any example code, don't think the company I work for would be too happy giving away work for free!
