Re: [lwip-users] LwIP issue on TMS570

[address@hidden]

Am 16.04.2019 um 17:23 schrieb Thomas Drage:
> Hi,
>
> I have an implementation using lwIP on a TI TMS570LC4357 LaunchPad which
> exhibits a strange problem, and I'm hoping someone can provide some
> insight or tips :)
>
> 1. The first message received calls tcp_recv instantly and is processed.
>
> 2. The second message might take 5 - 10s until tcp_recv is called.
>
> 3. The third etc. can take a very long time (or forever) between sending
> the data to the TMS570 and the getting callback.

That almost sounds like the driver is somehow missing RX packets? A
common bug was/is that the driver only receives one packet per ISR call,
when (due to code runtime) multiple packets can be received before the
ISR returns.

> My code is based on this echo-server:
> https://github.com/dreamcat4/lwip/blob/master/contrib/apps/tcpecho_raw/echo.c

Why use a copy if you can use the original?

https://github.com/lwip-tcpip/lwip/

Regards,
Simion

> Note that in the initial implementation of the echo server this problem
> doesn't occur, however, my implementation separates reading and writing
> (e.g. it is not an echo server anymore). So on reading, the message is
> parsed/stored, then instead of sending it back the pbuf is freed and
> tcp_recved called. If I insert a tcp_write after I have stored the
> message and just send some random (constant) string back before I
> deallocate the pbuf - everyone works once more (there is no delay on
> receiving subsequent packets). I struggle to explain why this is the
> case. Does anyone see a problem with the echo server code that would
> make it stop working if it's not being asked to send data?
>
> It seems almost a little like this:
> https://e2e.ti.com/support/microcontrollers/hercules/f/312/t/675413?RM46L852-Modbus-Over-TCP-IP-control-hand-in-TCP-Rx-interrupt
>
>
> I have attached my code. Note that in the function cont_read, if I
> remove the line "tcp_write(tpcb, "ACK", 3, 1);", I start getting the
> extreme delays before receiving subsequent messages.
>
> Thanks,
>
> Thomas Drage