[ECOS] Serial comms

Sergei Gavrikov sergei.gavrikov@gmail.com
Wed Apr 15 07:24:00 GMT 2009

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!

while (1) {
    // ...
    res = read(fd, buf, 4096);
    buf[res] = 0;
    // ...

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 


Then learn eCos programming.


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