Do we _really_ have to go through such pain just to write some in-line
assembly in gcc? THAT could sure use some streamlining in the avr-gcc
compiler. In-line assembly is pretty much a must for embedded work.
Rather than do that I'll write assembly functions and link them in, this
is just too ugly to contemplate!
IMO,
DLC
> Ruud Vlaming schreef:
>> Hi,
>>
>> There are a couple of ways to use i/o address in assymbly.
>> Below i used a some:
>>
>> #define _EEARL_ "0x1E"
>> uint8_t portFSReadByte(unsigned char * pAddress)
>> { uint8_t result;
>> asm volatile ( \
>> "in r26, __SREG__ \n\t"
>> "cli \n\t"
>> "out %2, %A0 \n\t"
>> "out "_EEARL_", %B0 \n\t"
>> "sbi __EECR__, 0 \n\t"
>> "in %A0, 0x1D \n\t"
>> "out __SREG__, r26 \n\t"
>> "" :"=r" (result) :"0" (pAddress), "I" (_SFR_IO_ADDR(EEARH)) : "r26"
>> );
>> return result; }
>>
>> (1) You can define a constant, like i did for _EEARL_
>> This is nice but no so portable.
>> (2) You can use the asm paramter list, like for EEARH
>> Also nice, but errorprone, since i keep making mistakes in
>> numbering, especially when you have many parameters and
>> have to change something.
>> (3) The best thing to have would be something like __EECR__,
>> resembling the definition for __SREG__, but that does not
>> compile right now.
>>
>> Is the latter possible somehow? Or are there other solutions?
>
> You could go for option 2 if you use syntax like this (took this from
> eeprom.h)
>
> __asm__ __volatile__ (
> "/* START EEPROM WRITE CRITICAL SECTION */\n\t"
> "in r0, %[__sreg] \n\t"
> "cli \n\t"
> "sbi %[__eecr], %[__eemwe] \n\t"
> "sbi %[__eecr], %[__eewe] \n\t"
> "out %[__sreg], r0 \n\t"
> "/* END EEPROM WRITE CRITICAL SECTION */"
> :
> : [__eecr] "i" (_SFR_IO_ADDR(EECR)),
> [__sreg] "i" (_SFR_IO_ADDR(SREG)),
> [__eemwe] "i" (EEMWE),
> [__eewe] "i" (EEWE)
> : "r0"
> );
>
> This makes the code far more readable IMHO. For more info on the %[ ]
> notation take look at:
> http://gcc.gnu.org/onlinedocs/gcc-4.3.0/gcc/Extended-Asm.html
>
> HTH
>
> Wouter
>
>
>
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>
--
Dennis Clark
TTT Enterprises
--
Dennis Clark
TTT Enterprises
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