1 Topic by pcu (edited by pcu 2014-03-20 06:17:49)

  • pcu
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Topic: [solved] long time to send one frame

Hello,

I work on ssl communication between two STM32 cards with crypto enabled.
I see that there is a very long time between two packets exchange.

In the capture example in attachment, I use one STM32 in server and a PC as client, but this is the same problem.
See packet between 17 and 19 (in black), there is +- 2,5 seconds.

I checked the communication between two computers, and there is no blocking.

It is nomal with STM32 (or in general with embedded)  this blocking time?
Thank you.

Pierre

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  • pcu
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Re: [solved] long time to send one frame

Hello,

I traced with a timer to find out where is the blockage.
it is located in integer.c => mp_exptmod_fast level () in the loop for (;;).
It takes two times one second.

Can I reduce the time?

stack copy:
0B1F437 [Embedded C/C++ Application]   
    0B1_F437_V04.00.00.elf   
        Thread [1] <main> (Suspended : Breakpoint)   
            mp_exptmod_fast() at integer.c:1,871 0x802bd28   
            mp_exptmod() at integer.c:778 0x802a288   
            RsaFunction() at rsa.c:214 0x8027fec   
            RsaSSL_Sign() at rsa.c:440 0x8028322   
            SendCertificateVerify() at internal.c:8,126 0x8022b04   
            CyaSSL_connect() at ssl.c:4,140 0x801ba26   
            CyaSSL_negotiate() at ssl.c:304 0x801a25c   
            SendData() at internal.c:5,479 0x802181c   
            CyaSSL_write() at ssl.c:436 0x801a29a   
            gateway_tcp_thread() at gateway_tcp.c:95 0x8006c50   
            <...more frames...>   


Kind regards,
Pierre

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  • pcu
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Re: [solved] long time to send one frame

It is solved now.

The solution is to build the at least the integer.c with optimtisation. For better performance I build the entire wolfSSL embedded SSL library with -Ofast flag.

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