microseconds delay function in IAR EWARM

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microseconds delay function in IAR EWARM

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Started 3 years ago by Harinath
Latest reply from Harinath

Harinath
Member

I saw the GitHub repo of libmaple/delay.h

static inline void delay_us(uint32 us) {
us *= STM32_DELAY_US_MULT;

/* fudge for function call overhead */
us--;
asm volatile(" mov r0, %[us] \n\t"
"1: subs r0, #1 \n\t"
" bhi 1b \n\t"
:
: [us] "r" (us)
: "r0");
}

I would like to write the same function in IAR EWARM 6.3
I get the following error if I use the same code:

Error[Og006]: Syntax error in inline assembly: "Error[41]: Bad label"

Anyone who has writing code in IAR embedded workbech, suggestions please .

Posted 3 years ago #
tormod
Member

It would have been useful if you told us which line is 41. Anyway, the label "1" (the number one) is a local label, referred to by "1b" (b for backwards) [1]. Maybe local labels or numbers as labels are not allowed in IAR. Try replacing them with a text label like "loop_us". The stuff between the colons after the assembly code string is for telling the compiler which registers and variables should be used for input and output, and this might be GCC specific [2]. I think you can use the C variable name directly in IAR assembly, so that the first line would be " mov r0, us \n\t" and the colon-separated stuff can be skipped.

Or you can just code it in C and calibrate STM32_DELAY_US_MULT accordingly: Declare "us" volatile and use: while (us--);

[1] http://sourceware.org/binutils/docs-2.23.1/as/Symbol-Names.html#index-local-labels-217
[2] http://gcc.gnu.org/onlinedocs/gcc/Extended-Asm.html

Posted 3 years ago #
Harinath
Member

The error comes only when the function is called & compiled, doesn't appear when not called. Also, The above error appears at the last line of code( but this code line number is not 41 in my header file).
I modified according to your suggestions & compiled, but still no luck.
Is this assembler code is equivalent of C language version :
while (delay_us--);

The following link may help us go little forward:
http://supp.iar.com/Support/?note=31237&from=search+result

Thank you

Posted 3 years ago #

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