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FreeRTOS lwIP

Posted by alpha86 on July 9, 2012
I am having a hard time debugging my lwIP application. I have a modified copy of the freeRTOS+ demo and it has been working good so far. My lwIP application runs well but when I use SPI together with lwIP task running I always end up at hardfault.

I have narrow down to the function, and it seems to occur at lwip_recv() function. I am not sure how the FreeRTOS port of lwIP is implemented, will definitely appreciate any info about it.

I will also like to know:
1) if the freeRTOS port of lwIP is thread/ISR safe?
2) I try to dig into the code, and I found this xInsideISR at sys_arch.c. I will like to know if this variable is an internal variable or should I use it in my code? I did a search on this variable and I dont seem to see any changes on this variable (only logic test). The variable definition is copied here for reference:

/* Very crude mechanism used to determine if the critical section handling
functions are being called from an interrupt context or not. This relies on
the interrupt handler setting this variable manually. */
volatile portBASE_TYPE xInsideISR = pdFALSE;

3) I understand the lwIP requires a tcp timer. is freeRTOS using the hardware timer or software?

hope to get some info about it, thanks

RE: FreeRTOS lwIP

Posted by Richard on July 15, 2012
“1) if the freeRTOS port of lwIP is thread/ISR safe?”


lwIP itself is not thread safe, but the way FreeRTOS uses lwIP in the example is fine and can be copied. For example, the sockets API uses message queues to send data to the TCP thread so the TCP processing only occurs in one thread.

“I try to dig into the code, and I found this xInsideISR at sys_arch.c. I will like to know if this variable is an internal variable or should I use it in my code?”


xInsideISR is used because some of the lwIP port functions are called from both the task level and the ISR level - and the API function to call needs to be different in each case. Therefore, the variable is only used in the Ethernet interrupts that might call the lwIP port layer. It is not normally needed.

“3) I understand the lwIP requires a tcp timer. is freeRTOS using the hardware timer or software?”


lwIP manages the timing itself, FreeRTOS does not provide anything explicitly for this purpose.

Regards.


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