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Re: printf and diag_printf go to nowhere

On Sat, 11 Apr 2009 18:44:34 +0200, Sergei Gavrikov <> wrote:

On Sat, Apr 11, 2009 at 06:15:50PM +0300, Sergei Gavrikov wrote:
On Sat, Apr 11, 2009 at 12:42:50PM +0200, Robert Brusa wrote:
> Hi
> When running the example serial.c that comes with ecos-3.0, I get no
> output on the serial i/f of my AT91SAMX512-based board. I am using a
> configuration where I have enabled hardware drivers for ser0 and ser1 and
> disabled ser2 (see attachment).
> serial performs a lookup for /dev/haldiag - and fails. In fact, this
Ups, I missed this. Of course it will be, because, you have disabled
*SERIAL2 == your HAL's /dev/haldiag (read the below's explanations)
there is

cdl_component CYGPKG_IO_SERIAL_ARM_AT91_SERIAL2 { user_value 0 };

in your ECM.

My assumes the below were based on that what SERIAL2 device is alive.
But that is not wrong.


> string is not present in my configurations ecc-file. What I find there
> is: /dev/ttydiag. But when changing haldiag to ttydiag, the result is the
> same: No output on ser0 or ser1.


Now I knew your target's name and I can know what is it. So, it has 3
serial channels (I did not know about). According HAL, diagnostic and
debug channels are asigned with channel 2 (as you named it "ser2"). So,
all diagnostic output, by default, will be appear on the diagnostic
channel or at the "ser2", won't it?

// it should appear at "ser2"
diag_printf("test string\n");

Unfortunatly, I can only guess what you want to have. Let's assume, that
you want to see the output the above on "ser0". In this case you have to

    user_value 0;

for "ser1" it will "user_value 1" (by default it is equal 2 == "ser2").

Let's look on examples/serial.c again and your ECM options. I noted that
you do not tweak the option the above.

serial.c:83:printf("Starting serial example\n");

According the attached ECM, your printf() will print on the device

    user_value "\"/dev/ttydiag\""

So, printf will be to use diagnostic channel ("ser2"), becuase, the
above option points on "/dev/ttydiag". Where did you expect the output?
It seems for me, it will appear on "ser2".

serial.c:85:err = cyg_io_lookup( "/dev/haldiag", &handle );

The "/dev/ttydiag" is a device name (a generic diagnostic device name).
By default, when an eCos cdl_componet CYGPKG_IO_SERIAL_TTY_TTYDIAG is
enabled, it uses itself a layered device with name "/dev/haldiag". Look,
please, for a reference at


and you will see how the device's names are assigned with the layered
devices (dep_names) acording CDL options.

The first and non-layered `/dev/haldiag' device exactly is

Note: about a DEVTAB_ENTRY internals you can find information by a link
the below (look at the chapter's name as on "how-io-driver-works")

Well, I knew that "/dev/haldiag" (with your settings) is "ser2".

> On the other hand, when changing to /dev/ser0 or /dev/ser1, I get this
> particular line on the ser0 or ser1 interface - as expected. But all
> other output generated by printf-statements still is "unvisible". Is this

Of course, particular, I can assume that that line

"serial example is working correctly!\n";

will appear on "ser2".

And when you changed CYGDAT_LIBC_STDIO_DEFAULT_CONSOLE (/dev/ser0,
/dev/ser1), your printf's will be there, but not on /dev/haldiag.

Now you knew what "/dev/ttydiag" is by default, and I not saw that you
assigned default console with another device. So, printf will just use
haldiag_putc (=HAL_DIAG_WRITE_CHAR) to out strings on "ser2". And it's
no deal that you enabled cdl component CYGPKG_IO_SERIAL_DEVICES.

Well, on the not-a-reduced targets (with GDB support) those printf's, by
default, all will appear just in GDB (on diagnostic | debug channel).

So, if you know where you want to see the diagnostic output, specify

I hope, that was it.


> a bug or do I get something wrong?
>   Robert

> --
> Before posting, please read the FAQ:
> and search the list archive:

Hi Sergei
thank you for your help. Following your script I achieved that I get the following output on uart1:
Starting serial example
Found /dev/haldiag. Writing string....
serial example is working correctly!
I think I wrote the string. Did you see it?
Serial example finished
An this is absoutely great. what I want at the end is to use:
serial_0 for efficient bidirectional (interrupt driven) communication
serial_1 should act as my console-device (also efficient)
serial_2 is not wired on my board, but I possibly could use it to access the output to serial_2 through my JTAG debugger. I will have to test this.

What I do not yet understand: Is diag_printf in my current configuration (see attachment) now going to serial_2 using an at91-specific efficient driver or still the polling write routine? Or none of both, because there is a conflict?

I coninue testing. I think much of what I want to achieve is now working. It looks good. Thanks

Attachment: ekdef_23.ecm
Description: Binary data

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