Microseconds delay assembler inline routine IAR EWARM 6.3

[harinath]

Posted on December 19, 2012 at 07:19

I needprecise microseconds delay routine in myapplication ( uses STM32F103RE)

I saw

https://github.com/leaflabs/libmaple/blob/master/libmaple/include/libmaple/delay.h

for microseconds delay routine. It has the following:

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'm trying to rewrite this routing in IAR EWARM 6.3 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 hasexperience in writing code using IAR embedded workbech, suggestions pleas

[frankmeyer9]

Posted on December 19, 2012 at 17:35

I think it is nothing else than a disguised assembler version of

while (delay_us--);

And I bet there is no 1:1 relation between the contents of

delay_us

, and the time spent there in microseconds...

[harinath]

Posted on December 20, 2012 at 02:08

Thank you for pointing out c version. But I prefer assembly version to check out which one works closer to 1 microsecond.

[Tesla DeLorean]

Posted on December 20, 2012 at 02:43

static void delay_us(uint32_t us)
{
us *= STM32_DELAY_US_MULT;
us--;
asm('' mov r0, us 
''
''loop: subs r0, #1 
''
'' bhi loop 
'');
}

[harinath]

Posted on December 21, 2012 at 06:42

Sorry for the late reply.

The following errors are shown when compiled. Do we need to activate any settings in IDE ?

The following link may help us to resolve:

http://supp.iar.com/Support/?note=31237&%3bfrom=search+result

Thank you

[frankmeyer9]

Posted on December 21, 2012 at 10:58

Don't know the IAR toolchain in detail, but C level variables usually get prepended by a '_' in the assembler/linker stage. I would try '_us' instead.

And I'm not sure, lacking the IAR detailled knowledge, how you tell the compiler that the variable 'us' is manipulated in assembler code.

[Tesla DeLorean]

Posted on December 21, 2012 at 13:31

I used IAR EWARM 6.40.3.4115, worked there. Why not just put it in startup.s in straight assembler?