Re: Re: Digest from [email protected]

Robert
I developped a device based on pulse measurement with 52223 and so I needed 
to handle with captures.
Although I´m also a "original" hw guy (concerned on bits/bytes etc) , I 
concluded that many times is not worth manipulate variables
smaller then 32bits in machines like ColdFire.The "price" is the same
For my application, wich seems to be similar with your,  I (lazily?) did 
sonething like this:

uint32 current_value
uint32 new_value
uint32 old_value_value

current_value="hw_counter"   // (MCF.....
if(old_value>=current_value)
{
    new_value=old_value-current_value;
}
else
{
    new_value=current_value-old_value;
}
old_value=current_value;
This code runs in the interrupt_routine.

Good luck ...
Ricardo Raupp





----- Original Message ----- 
From: "Robert Ritchey" <[email protected]>
To: "Ricardo" <[email protected]>
Sent: Monday, September 15, 2008 11:32 AM
Subject: [ColdFire] Re: Digest from [email protected]


Hi Mark,
Thanks for that too.  I am afraid I am mostly a
hardware guy so this is about the
only C compiler I have right now. In the past I
did most of my work in assembly
on the MSP430.

Which brings me to one last question if I could
impose.  Basically what I am doing
here is capturing a pulse by a time to determine
the pulse width.  I capture the
rising and falling edges on a counter that is modulo 16 bits.  The MSP430 is 
a
16-bit machine so to get the pulse width I just
subtracted the falling edge from the
rising edge value and got a positive value.  The
reason I went to signed shorts on
the coldfire is that I saw in the assembly it was
loading the shorts with zero extend
and then doing a 32-bit subtract.  I don't think
this will give me the correct value so
I went to signed shorts and it does.  You
suggested going to unsigned shorts but
I don't think this will work.  Am I missing something simple here?   Thanks,

At 12:00 AM 9/15/2008 -0500, [email protected] wrote:
>From: "Mark Butcher" <[email protected]>
>To: <[email protected]>
>Subject: AW: [ColdFire] Re: Digest from  [email protected]
>Date: Sun, 14 Sep 2008 22:57:40 +0200
>
>Hi Bob
>Just a side note. I work with several compilers and the CW warnings are in
>fact quite extreme and I do in fact keep them off since otherwise the
>casting required also becomes rather extreme.
>My solution is to compile the project with GCC and Visual-Studio 
>C-compilers
>and ensure that they don't give any warnings - assuming that this is the
>case, then I am satisfied.
>Regards
>Mark
>
>
>
>-----Ursprüngliche Nachricht-----
>Von: [email protected] [mailto:[email protected]] Im
>Auftrag von Robert Ritchey
>Gesendet: Sonntag, 14. September 2008 16:44
>An: [email protected]
>Betreff: [ColdFire] Re: Digest from [email protected]
>
>Hi Mark,
>Thank you very much for the detailed explanation.  Its very clear now.
>I think with this help I can make some informed decisions on how to
>declare variable types.
>
> >
> >typedef struct
> >      {
> >      short            RiseEdge;                       /* Pulse rising
> >edge time                       */
> >      short            FallEdge;                       /* Pulse
> >falling edge time                      */
> >      } ChanInStruct;
> >
> >bool TxPulseOffset(short *Offset)
> >{
> >      short   PulseWidth;
> >                     /* Pulse width                          */
> >      PulseWidth = (short)(pRxChannelInput->FallEdge -
> >pRxChannelInput->RiseEdge);        /* Pulse width is falling minus rising
>*/
> >}

-Bob
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