AVR-Chat

I do it all the time!

Martin Jay McKee

On Sat, Feb 2, 2013 at 2:47 PM, englsprogeny1 <englsprogeny1@yahoo.com>wrote:

> **
>
>
>
> Thanks guys! I was thinking in the c++ world again...
>
>
> --- In AVR-Chat@yahoogroups.com, Martin McKee wrote:
> >
> > Pass-by-reference is only available in C++. In C you have to pass in a
> > pointer, and, for that, you use * as has been mentioned.
> >
> > void CalculateOffTime( uint8_t duration, offTimeStruct* eventOff )
> >
> > then, eventOff->endMinute = ...
> >
> > Martin Jay McKee
> >
> > On Sat, Feb 2, 2013 at 2:22 PM, Charlie H wrote:
> >
> > > **
>
> > >
> > >
> > > I agree with Clark on the pointer issue. The & should be * in the
> > > function declaration.
> > >
> > > Charlie
> > >
> > >
> > > On 2/2/2013 4:17 PM, englsprogeny1 wrote:
> > > >
> > > > I've updated the struct, thanks.
> > > >
> > > > I want to be able to update the values within the struct (depending
> on
> > > what 'instance' is passed into the function).
> > > >
> > > > This is why I am doing 'pass by reference' (by the address)
> > > >
> > > >
> > > > I get the following error:
> > > >
> > > > menu.c:1732: error: expected ';', ',' or ')' before '&' token
> > > >
> > > > This is referring to the prototype portion of the function
> definition.
> > > >
> > > >
> > > >
> > > > void CalculateOffTime(uint8_t duration, offTimeStruct &eventOff)
> > > >
> > > >
> > > >
> > > > Any more ideas?
> > > >
> > > >
> > > >
> > > > --- In AVR-Chat@yahoogroups.com, Charlie H wrote:
> > > >> It looks like you are expecting the address of the struct passed to
> your
> > > >> function but not using the address in the function. Try it this way:
> > > >>
> > > >> void CalculateOffTime(uint8_t duration, offTimeStruct eventOff)
> > > >> {
> > > >> ...
> > > >> }
> > > >>
> > > >>
> > > >> Also, I think the typedef is wrong. Try it this way:
> > > >>
> > > >> typedef struct
> > > >> {
> > > >> uint8_t endMinute;
> > > >> uint8_t endHour;
> > > >> } offTimeStruct;
> > > >>
> > > >>
> > > >> HTH,
> > > >> Charlie
> > > >>
> > > >>
> > > >> On 2/2/2013 2:51 PM, englsprogeny1 wrote:
> > > >>> Simple C question.. I guess that I am blowing! Maybe I didn't get
> > > enough sleep last night....
> > > >>>
> > > >>>
> > > >>> Using AVR Studio 4.0 with GCC
> > > >>>
> > > >>> 1. I create a type that is a struct
> > > >>> 2. I create multiple 'instances' of this type.
> > > >>>
> > > >>>
> > > >>> I get the following errors when I Build All:
> > > >>>
> > > >>> menu.c:1729: error: expected declaration specifiers or '...' before
> > > 'offTimeStruct'
> > > >>> menu.c:1742: error: 'eventOff' undeclared (first use in this
> function)
> > > >>>
> > > >>>
> > > >>>
> > > >>>
> > > >>> typedef struct offTimeStruct
> > > >>> {
> > > >>> uint8_t endMinute;
> > > >>> uint8_t endHour;
> > > >>> };
> > > >>>
> > > >>> offTimeStruct light1;
> > > >>> offTimeStruct rocket;
> > > >>>
> > > >>>
> > > >>>
> > > >>> //menu.c: Line 1729
> > > >>> void CalculateOffTime(uint8_t duration, offTimeStruct &eventOff)
> > > >>> {
> > > >>> //menu.c: Line 1742
> > > >>> eventOff.endMinute = 1;
> > > >>>
> > > >>> }
> > > >>>
> > > >>>
> > > >>>
> > > >>>
> > > >>> funtion call from Main()
> > > >>>
> > > >>>
> > > >>> CalculateOffTime(1, light1);
> > > >>>
> > > >>> Thanks for your ideas guys!
> > > >>>
> > > >>>
> > > >>>
> > > >>>
> > > >>>
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> >
>
>  
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