"#define" is not working with the MC9S12XS128

[aceshigh99]

I have a question on what I figured to be a rather simple bit of coding that is not working the way I would expect it to... I've assigned labels to some output pins on the MC9S12XS128 (port A, specifically) using #defines, and then tried to

#define     COIL_05_CTL     PORTA

#define     COIL_05_PIN     BIT5

ubyte     LAST_COIL_CTL;

ubyte     LAST_COIL_PIN;

case 5:

     LAST_COIL_CTL = COIL_05_CTL;  // Assign coil 5 control to last coil control

     LAST_COIL_PIN = COIL_05_PIN;  // Assign coil 5 output pin to last coil pin

LAST_COIL_CTL &= (~LAST_COIL_PIN);  // Turn off pin 5 of PORT A - does not work

This last command DOES NOT turn off pin 5 of PORT A; however, the following line of code DOES turn off the pin, as expected:

 COIL_05_CTL &= (~COIL_05_PIN);  // Turn off pin 5 of PORT A

Any idea as to why the #define can't be assigned to simple ubyte variable and manipulated accordingly?  I also tryed (ubyte) castings, which did not help:

case 5:

     LAST_COIL_CTL = (ubyte)COIL_05_CTL;  // Assign coil 5 control to last coil control

     LAST_COIL_PIN = (ubyte)COIL_05_PIN;  // Assign coil 5 output pin to last coil pin

Thanks in advance.

[Lundin]

The problem isn't syntax-related, it is your algorithm that doesn't make sense.
Change it to this:



LAST_COIL_PIN = COIL_05_PIN; // Assign coil 5 output pin to last coil pin

COIL_05_CTL &= ~LAST_COIL_PIN; // Turn off pin 5 of PORT A

Message Edited by Lundin on 2010-02-03 09:55 AM

[pgo]

Dear acehigh99,

Perhaps I have misunderstood what you are trying to do.  I assumed that you wanted to be able to set up access to an arbitrary pin on an arbitrary port and then (later) access that pin.  If you are able to restrict to a single port then Lundin's suggestion is much superior.

bye

[aceshigh99]

Your suggestion worked very well.  Just needed to reference the hardware by address rather than directly.  You were correct...thanks!

[pgo]

Dear acehigh99,

PORTA is a memory location.  When used as a rvalue (ie. on the right of an assignment) its contents are used, so the line:

LAST_COIL_CTL = COIL_05_CTL; 

Just copies the _contents_ of PORTA to  LAST_COIL_CTL.

Your code is doing something like the following:

int i;

int j;

 ......

j = i ;

j = 33;

but you are expecting i to change!

The following code will do what you want (for a different CPU but changes should be obvious):

#include <hidef.h> /* for EnableInterrupts macro */
#include "derivative.h" /* include peripheral declarations */

typedef unsigned char U8;

#define     COIL_05_CTL     PTAD
#define     COIL_05_PIN     (1<<5)

U8     *LAST_COIL_CTL;
U8     LAST_COIL_PIN;


void main(void) {

  EnableInterrupts; /* enable interrupts */
  /* include your code here */

LAST_COIL_CTL = &COIL_05_CTL;  // Assign coil 5
LAST_COIL_PIN = COIL_05_PIN;  // Assign coil 5 pin
*LAST_COIL_CTL &= (~LAST_COIL_PIN);  // Turn off pin 5 of PORT A
}

 Hope this helps.

A further tip - It is sometimes useful to to look at the Pre-processed code to see how you macros expand.  You can do this by right-clicking and select Preprocess.  You can also look at the assembly language generated by selecting Disassemble on the same menu.

bye