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Re: Serial comms




Sergei Gavrikov-4 wrote:
> 
> On Wed, Apr 15, 2009 at 02:01:39AM -0700, grahamlab wrote:
>> 
>> 
>> 
>> Sergei Gavrikov-4 wrote:
>> > 
>> > On Tue, Apr 14, 2009 at 03:04:29AM -0700, grahamlab wrote:
>> >> 
>> >> Hello everyone
>> >> I am relatively new to eCos so please forgive me my questions seem
>> naive.
>> >> I am developing software targeted at the STM3210e dev board and am
>> trying
>> >> to
>> >> get serial comms going between this board and a program running under
>> >> ubuntu
>> >> via virtual box on my PC
>> >> I have a serial link between the PC and the dev kit (UART1) that uses
>> >> ttyS0
>> >> to load the ecos program via gdb. This works, I can download and
>> execute
>> >> an
>> >> eCos program on the Dev board.
>> >> I have another serial link between my PC and the dev kit (UART2).
>> >> I have written 2 programs - one using eCos and one to run under
>> ubuntu.
>> >> The eCos program opens the /dev/ser1 device and writes a string to
>> that
>> >> device and awaits a reply.
>> >> The ubuntu opens /dev/ttyS1 and waits for a message and then writes
>> back
>> >> an
>> >> acknowledgment.
>> >> 
>> >> When these two programs are run I get the following results.
>> >> 
>> >> When the ecos program sends its data the ubuntu program receives alot
>> of
>> >> data from the Redboot monitor and then the data from the ecos program.
>> It
>> >> then blocks on the write. The ecos program has blocked on the read.
>> >> 
>> >> Why do I get data from the Redboot monitor and why do both programs
>> >> block.
>> >> I have attached both programs 
>> >> http://www.nabble.com/file/p23036433/hello.cpp hello.cpp ,
>> >> http://www.nabble.com/file/p23036433/SerialTest.cpp SerialTest.cpp 
>> >> 
>> >> Thank you for your time
>> >> Graham
>> > 
>> > Graham, it seems for me, your eCos application quite crashes (board
>> > resets itself) and you see/get the Redboot's startup screen in your
>> > program. Your code is terrible, you do not check return-codes!
>> > 
>> > hello.cpp:
>> > while (1) {
>> >     // ...
>> >     res = read(fd, buf, 4096);
>> >     buf[res] = 0;
>> >     // ...
>> > }
>> > 
>> > SerialTest.cpp:
>> > while (1) {
>> >     // ...
>> >     int             b = read(fd, &buf[0], 4096);
>> >     buf[b] = '\0';
>> >     // ...
>> > }
>> > 
>> > How do you think, What will happy on buf[-1] = 0 ? Read about the
>> return
>> > values of read(), write().
>> > 
>> > man 2 read
>> > man 2 write
>> > 
>> > Your while() blocks are terrible things which will eat all CPU time if
>> > they will work at all.
>> > 
>> > Your hello.cpp is written for PC and that is almost just an echo
>> > program.  Why do not use terminal program (minicom, hyperterm) at first
>> > to debug the eCos termios program? It seemed for me that you are not
>> > only "new" to eCos. Why we took a time to stand up GDB for you? 
>> > 
>> > Learn programming, learn C 
>> > 
>> > http://en.wikibooks.org/wiki/C_Programming
>> > 
>> > Then learn eCos programming.
>> > 
>> > 
>> > Sergei
>> > 
>> > -- 
>> > Before posting, please read the FAQ:
>> http://ecos.sourceware.org/fom/ecos
>> > and search the list archive: http://ecos.sourceware.org/ml/ecos-discuss
>> > 
>> > 
>> > 
>> Sergei
>> I have used the mincom program to receive a test string from ecos
>> When I use a PC program of my making to read a string I receive data from
>> redboot before I receive the test string. I do not know why this is the
>> case
>> and would appreciate any explanation
>> 
>> Graham
> 
> On start Redboot (by default) outs own startup screens an both serial
> channels. You can see it. Run on two consoles
> 
> on 1st console:
> stty speed 38400 -F /dev/ttyS0
> cat /dev/ttyS0
> 
> on 2nd console:
> stty speed 38400 -F /dev/ttyS1
> cat /dev/ttyS1
> 
> connect cables to the board and then press a Reset button. You will see
> that data will come on both consoles.
> 
> So, when board is reset, Redboot's banner already exists in PC's serial
> buffer, but that lines has been not read yet (/dev/ttyS1). When you run
> your PC program, it reads that portion of lines and then it read next
> incoming data. So, your program should flush serial buffer before to
> start that read loop.
> 
> 
> Sergei
> 
> -- 
> Before posting, please read the FAQ: http://ecos.sourceware.org/fom/ecos
> and search the list archive: http://ecos.sourceware.org/ml/ecos-discuss
> 
> 
> 
Thanks for the info Sergei
Will the Redboot banner get output when I start my ecos program. This is
what seems to be happening
I flush the serial buffer before reading data in the PC program 
When I run the PC program it is waiting for input.
I then run the ecos program and get the redboot stuff in the PC program.

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-- 
Before posting, please read the FAQ: http://ecos.sourceware.org/fom/ecos
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