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Re: Serial comms




Sergei Gavrikov-4 wrote:
> 
> On Wed, Apr 15, 2009 at 03:48:22AM -0700, grahamlab wrote:
>> 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.
> 
> GDB your eCos program step-by-step and find when it crahes and when
> board is reset. You have a power -- GDB.
> 
> 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 already done this - no crash occurs
It is a simple program that just writes a string. as soon as the write
operation occurrs I get the redboot banner on the PC program. I get the same
result using the serial2 example program
-- 
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-- 
Before posting, please read the FAQ: http://ecos.sourceware.org/fom/ecos
and search the list archive: http://ecos.sourceware.org/ml/ecos-discuss


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