[lwip-users] Basic Design Question

[Spies, Dominik]

Hi!

I have some basic questions about the software design with the lwIP stack.
Currently I'm using a port of FreeRTOS with lwIP. This port uses lwIP with NO_SYS true and calling it in one single task in a infinite loop.

Every cycle ethernetif_handlepackets is called, and after that depending on some timing things the tmr functions.

So, I do not think this is a good solution. My first idea is:

Two Tasks, on handling the incoming packets, blocked via queue. An ISR handles incoming packets and write it to the queue.

The second tasks executes all tmr functions.

Because a preemptive scheduler is used, the lwip stack stuff has to be protected via mutexes.

Two tasks for recieving/tmr processing is overhead. So how could I do that in one task? I can either wait for a specified time (tmr stuff) OR for an event (incoming packet) but not both (This is by design of FreeRTOS I think). Suggestions?

Or is it in my case generally better to use the socket api, especially regarding to RAM consumption? I did'nt spent any time on considering to use it because rawapi.txt says it uses much more ram, and I do not have unlimited amount (40kb total) of ram. I do not know how much more ram the socket api needs, but maybe it is not much more or even less than with my "two tasks and queue... " solution.

I hope this is not to basic for this list, but I'm no expert in realtime kernels or embedded systems design, so I hope some of you experts can spend some time helping a beginner ;)

Thanks.