You'll have to pass the address of the port and a bitmask instead.

For example:

void MAX3110_WRITE(  unsigned char c, unsigned char *port, unsigned char
mask )
{
     MAX3110_SETSPI();                     // setup SPI port for MAX3110
     while(!(MAX3110_STATUS() & 0x4000));
          *port &= ~mask;        // select MAX3110
          SPI_SEND(0x80);                            // write data command
          SPI_SEND(c);                                  // send the data
          *port |= mask;            // deselect the MAX3110
}

Bob Ammerman
RAm Systems

----- Original Message -----
From: "Nick Veys" <nick@VEYS.COM>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Friday, April 26, 2002 4:36 PM
Subject: [PIC]: Passing "bit" variables in Hi-Tech C


> I know there's plenty of C users here so here goes.
>
> I decided to at least try the plunge into the PIC C world, after all ASM
> it's starting to get old! :)
>
> So I am looking to write a few headers, one is for the MAX3110's I use.
> I need to have a chipselect line for each of them, so I can't just
> define it as there will be > 1.  I want to simply pass the "bit"
> variable I setup in the main program to the functions for the 3110 that
> way I can use lots of them.
>
> My problem is, PICC bitches when I put a bit in a parameter list for a
> function.
>
> Here's a sample:
>
> ------------------------------
>
> void MAX3110_WRITE(unsigned char c)
> {
>   MAX3110_SETSPI();                     // setup SPI port for MAX3110
>   while(!(MAX3110_STATUS() & 0x4000));
> //  chipselect = 0;                             // select MAX3110
>   SPI_SEND(0x80);                               // write data command
>   SPI_SEND(c);                                  // send the data
> //  chipselect = 1;                             // de-select MAX3110
> }
>
> ------------------------------
>
> This simply writes a byte to the 3110.  The chipselects are commented
> out, as when I add the bit to the parameter list, and uncomment them, as
> so:
>
> ------------------------------
>
> void MAX3110_WRITE(unsigned char c, bit chipselect)
> {
>   MAX3110_SETSPI();                     // setup SPI port for MAX3110
>   while(!(MAX3110_STATUS() & 0x4000));
>   chipselect = 0;                               // select MAX3110
>   SPI_SEND(0x80);                               // write data command
>   SPI_SEND(c);                                  // send the data
>   chipselect = 1;                               // de-select MAX3110
> }
>
> ------------------------------
>
> I get "bits must be either global or static" error.  So I make them
> static.
>
> ------------------------------
>
> void MAX3110_WRITE(unsigned char c, static bit chipselect)
>
> ------------------------------
>
> Now I get "bad storage class" error.
>
> So I read the manual. ;) I can't make them global since I need multiple
> ones, and this seems the simplest way, but sadly I find in the manual,
> "bit variables cannot be function parameters".  Argh.
>
> So any ideas on how to work around this limitation?  I could pass a
> PORT,BIT pair as a struct, but that seems messy.  There's gotta be a
> slick way to do this.
>
> nick@veys.com | www.veys.com/nick
>
> --
> http://www.piclist.com hint: To leave the PICList
> mailto:piclist-unsubscribe-request@mitvma.mit.edu
>
>

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