[sdiy] help...no make8() function in Arduino...converting PIC to AVR

[dan snazelle]

Ok

thanks everyone I will now try to absorb this and will also see if the code works!

very much appreciated






On Apr 11, 2012, at 1:21 PM, Veronica Merryfield wrote:

> The pre-processor uses textual substitution to expand macros
> 
> #define _mul (al, val) ((int)(((al)*(val))>>8)
> 
> used...
> 
> tmp2 = _mul (acc2, tmpamt);
> 
> becomes...
> 
> tmp2 = ((int)(((acc2)*(tmpamt))>>8);
> 
> before the compiler proper does it's thing.
> 
> 
> On 2012-04-11, at 10:13 AM, dan snazelle wrote:
> 
>> more specifically
>> 
>> in a macro
>> 
>> 
>> #define  _mul   (int)( a1*val>>8)
>> 
>> 
>> then when i go in and i do 
>> 
>> 
>> tmp2 = _mul (acc2, tmpamt);
>> 
>> how does the define know that acc2=a1 and tmpampt=val??
>> 
>> thanks
>> 
>> 
>> On Apr 11, 2012, at 12:57 PM, Olivier Gillet wrote:
>> 
>>> There's a cost associated to calling "proper" functions - parameters
>>> being pushed to the stack or moved to the right register, then a jump,
>>> the body of the function, a return, and moving the result from the
>>> output register to whatever register the result should be in. You
>>> don't want such small things to be functions - and that's probably why
>>> they were defined as macros in the first place! So you either have to
>>> define those as macro ; or as inline functions, using something like
>>> __attribute__((always_inline)) in the declaration. gcc might be smart
>>> enough to inline them without being forced to do so with the
>>> __attribute__, but it's not a very good thing to make such
>>> assumptions.
>>> 
>>> Olivier
>>> 
>>> On Wed, Apr 11, 2012 at 6:47 PM, dan snazelle <subjectivity at hotmail.com> wrote:
>>>> ok so if
>>>> 
>>>> 
>>>> make8  = (((var >> (offset*8)) & 0xff)
>>>> _mul  value = (int)( a1*val1>>8);
>>>> 
>>>> 
>>>> 
>>>> then since i dont quite understand the parentheses in define I could make 2 functions
>>>> 
>>>> 
>>>> 
>>>> byte make8(int var, byte offset)
>>>> {
>>>> byte result=(((var >> (offset*8)) & 0xff);
>>>> return result;}
>>>> 
>>>> 
>>>> 
>>>> and for the other function  (_mul)
>>>> 
>>>> 
>>>> int _mul (byte a1, byte val) {
>>>> 
>>>> int result=(int)( a1*val1>>8);
>>>> return result;
>>>> }
>>>> 
>>>> 
>>>> 
>>>> do those look right?
>>>> 
>>>> 
>>>> thanks
>>>> 
>>>> 
>>>> 
>>>> 
>>>> 
>>>> On Apr 11, 2012, at 12:00 PM, Martin Klang wrote:
>>>> 
>>>>> 
>>>>> what do they do on the pic?
>>>>> 
>>>>> make8 I found in the PIC C Compiler Reference:
>>>>> i8 = MAKE8(var, offset)
>>>>> Same as: i8 = (((var >> (offset*8)) & 0xff)
>>>>> 
>>>>> so that
>>>>>> tmpbyte1 = make8(tmp1, 1);
>>>>> 
>>>>> would be
>>>>> tmpbyte1 = (tmp1 >> 8) & 0xff;
>>>>> 
>>>>> and _mul() multiplies, right?
>>>>> 
>>>>> Looks like the code is specifically optimised for the pic instructions set -
>>>>> tmp1 is 16 bit, right? acc1 and val1 8-bit unsigned integers?
>>>>> 
>>>>> Presumably you can replace the two lines with
>>>>> uint8_t value = (uint8_t)( acc1*val1>>8);
>>>>> depending on data types, but would have to see some more code to know.
>>>>> 
>>>>> 
>>>>> hth,
>>>>> 
>>>>> /m
>>>>> 
>>>>> On 11 Apr 2012, at 16:25, dan snazelle wrote:
>>>>> 
>>>>>> can someone help me ?
>>>>>> 
>>>>>> i am trying to convert some PIC code to AVR
>>>>>> 
>>>>>> it is going fine except for 2 things
>>>>>> 
>>>>>> there is no make8() function and there is no _mul()
>>>>>> 
>>>>>> 
>>>>>> so code lines like this:
>>>>>> 
>>>>>> 
>>>>>> tmp1 = _mul (acc1, val1);
>>>>>> 
>>>>>> tmpbyte1 = make8(tmp1, 1);
>>>>>> 
>>>>>> 
>>>>>> do not work
>>>>>> 
>>>>>> 
>>>>>> 
>>>>>> i have been looking for the make8 function online so i can just write that function into my code but no luck
>>>>>> 
>>>>>> 
>>>>>> thanks for any help!
>>>>> 
>>>>> 
>>>> 
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