safeRTOS "Task safe" console output?

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Posted by Andrew Eldredge

on May 04 2012 15:08 PM

I often find myself relying on console output to debug code. I am starting up in using safeRTOS for some multitask work, but I have discoverd that printf seems to be poisonous to safeRTOS and safeRTOS is poisonous to printf. Shutting off the scheduler before a call to printf and then turning it back on again seems to prevent corruption of CIO, but It will also shut off the scheduler. Is there a "task-safe" method of getting information to the console>

Would a critical section do the job, or would it suffer corruption on tasks with sufficient priority to interrupt it.

What is the intent of the ustdlib.c? is it supposed to be interrupt safe?

Thank you for the help

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Posted by Michael S

on May 10 2012 12:25 PM

Genius9710 points

Hello team,

Is there an update available to this customer's inquiry?

Regards,

Michael

Regards,

Michael S.

ACSC Digital Apps

Posted by Matthew Staben

on Jun 11 2012 12:21 PM

Prodigy100 points

I found this question doing a google search for something else, but I once had the same problem - printf ( ) usage would cause CIO issues - thought I'd mention switching to the ustdlib (usprintf) libraries supplied by TI solved the problem for me - it's a pretty good library. Later, I came to realize that printf ( ) would work but I continued to use the ustdlib library functions. I don't recall what broke printf ( ) or got it working again, but just to get over the hump pick up the library functions and eventually you may find the combination that gets things to operate again. I think it had something to do with the system stack size that's configured in the eclipse environment, but it could be a number of things.

I'm using the LM3S9B96

Good luck.

P.S. You may want to start watching your stack usage. What I do is on declaration fill my stack space with 55's and then in the console perform a scan of where the 55's have been overwritten. Simpler than it sounds ...

Do this just before declaring the task (xTaskCreate ( ) )

i = 0;
while ( i < sizeof ( g_pul_TaskStack ) / 4 ) {
g_pul_TaskStack [ i ] = 0x55555555;
i += 1;
}

then, in the console when you tell it to analyze the stack

lp = &g_pul_TaskStack [ 0 ];

j = sizeof ( g_pul_TaskStack );

k = 0;
while ( k < ( j / 4 ) && *( lp + k ) == 0x55555555 ) {
k += 1;
}
usprintf ( Buf, "Len=%4d, Used=%4d, Free=%4dr\n", j, j - ( k * 4 ), ( k * 4 ) );