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Can’t assign pointer to a library function

 
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kender



Joined: 09 Aug 2004
Posts: 768
Location: Silicon Valley

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Can’t assign pointer to a library function
PostPosted: Wed Jul 23, 2008 6:09 am     Reply with quote

Colleagues,

I was trying to make a generic set_pwmX_duty(x, duty) function with a table of pointers: {set_pwm1_duty, set_pwm2_duty, …}. Unfortunately, I’m getting a compile time error:

Code:

typedef void (*fptypeSetPWMDuty)(int16 iPWM);   // pointer to the set_pwm12345_duty() function
typedef struct       // structure describing a channel
{
   ...
   fptypeSetPWMDuty  fpSetPWMDuty;  // pointer to the set_pwmX_duty() function
   ...
}

...

   g_sChannels[0].fpSetPWMDuty = set_pwm1_duty;    // compile-time error: Undefined identifier   set_pwm1_duty
   set_pwm1_duty(255);    // at the same time, this line of dummy code compiles just fine


PCWH 4.071 PIC18F4525

Cheers
- Nick
_________________
Read the label, before opening a can of worms.
Ttelmah
Guest







PostPosted: Wed Jul 23, 2008 8:03 am     Reply with quote

You will almost certainly find that set_pwmX_duty, is not really a 'function', but possibly a simple macro expansion. You will almost certainly have to put it into a 'wrapper' function, to allow a pointer to be generated.
Simple operations like this, which only transfer bytes into specific registers, with some basic manipulation on the way, are almost invariably not functions.

Best Wishes
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