Re: [lwip-users] delay on other parts of the program caused by sending data over TCP / LwIP is maybe blocking other interrupts?

[Julio Cesar Aguilar Zerpa]

Hello guys,

nevermind about the delay problem. It seems I was blocking the serial 
interface my self by sending too much debug data through serial way too 
fast.

However, the program still crashes when connected to the tcp client. It 
seems as if the connection breaks: I got the error -11 after a 
tcp_write. Any ideas why that would happen?

Thanks,

Julio


Am 17.11.2016 um 12:25 schrieb Julio Cesar Aguilar Zerpa:
> Hi there,
>
> I get data from a sensor every 65ms over asynchronous calls to the 
> serial interface of a microprocessor. I need to send that data over 
> ethernet (TCP) for visualization and debug, which I could do with the 
> help of LwIP and this mailing list.
>
> Now I noticed that sending the data over TCP causes a delay in the 
> receiving of the serial data ranging from 80ms to 130ms, which is bad. 
> I don't see how the serial interrupts are related to the ethernet 
> interface.  Does LwIP somehow blocks/stops serial interrupts from 
> ocurring?
>
> I use tcp_write and tcp_output(tpcb), which are inside a sys_timeout 
> callback and I call sys_check_timeouts in my main loop.
>
> I also noticed that if I comment tcp_output(tpcb), the server is not 
> able to send data returning a -1 (NO MEM) from tcp_write. However, the 
> serial data is received at the right frequency again.
>
> NOTE 1: It is not ideal but I don't care if a few ethernet packages 
> get lost or whatever once in a while, the important thing is to keep 
> all other parts of the system running as they should. Maybe there is a 
> way to signal LwIP when it is OK to send data?
>
> NOTE 2: I timed how long it takes my send function to send data (call 
> tcp_write and tcp_output) and it was 1ms, which means that even if 
> this functions are blocking, this time should not be a problem. So, 
> what is wrong?
>
> NOTE 3: I don't know if this is caused by my  configuration of 
> lwipopts.h but sometimes the microprocessor freezes while connected to 
> the visualization client. This doesn't happen when the ethernet 
> connection is not established.
>
> I hope you guys can help me again. I am using version 1.4.1 (raw api). 
> I am relative new with the LwIP, should I use the 2.0 version?
>
> Best Regards,
>
> Julio