8 sockets limitation W5500, DMA

Question

We have designed the W5500 in to a new product and are finding that some browsers are greedy in the number of open sockets they require. My questions are: Is 8 sockets a hard limit that cannot be extended? If so, is there a way around this problem? We are also unhappy with the SPI throughput using the STM32F, the inter-byte latency at 16MHz is about 90%. Is there driver code available that supports DMA?

Coccoliso · Answer

The number of sockets I really think that we can not increase because the W5500 has done so. If you’re referring to a web server 8 sockets limitation is a false problem because the connection is not permanent and must be resolved within REQUEST/RESPONSE timeout and should always end with a disconnect request at server side. In this regard, I have made an embedded server that receives requests 8 http simultaneous and I had no problems whatsoever because you’re forced to answer within 20 seconds. Before the browser loads the pure HTML that contains references to the link that then the browser requests cyclically with new requests to the server so every single element of a web page is requested by the browser to the server at different times and employ just different times in response (eg JPG images compared to HTML content) then the socket that sends an image becomes available after the socket that sends the pure html. Clearly if you want to transfer a continuous data stream (eg video streams) then it is different because you have to keep active communication channel and many MB (SD card content is claim). Clearly the examples that you find on the site will include the use of a buffer memory but you can do better. The advantage of the W5500 ( compared to W5100 maybe with RX_MASK bottleneck ) is that you can read the receive buffer directly byte by byte avoiding to hold a reception buffer into embedded and you’ll save a lot of memory… once it has received a request and is loaded in the receive buffer you can move easily in the buffer looking tokens and release the buffer when you’re done.