S12 / MagniV Microcontrollers中的主题 Re: Pass Port/Pin Address to Function

Pass Port/Pin Address to Function

Dustoor — Sat, 09 Jun 2012 02:59:10 GMT

Hello,

I am interested in writing a function that takes the address of a port as its argument, so that I can write to that port from within my function. E.g

// Definition

void foo(unsigned char *pin) {

*pin = 1;

// ...

}

// Call

foo(&PORTK_PK1);

However, the compiler gives me the following error at the function call:

Error: C1833: Cannot take address of this object

I am running this code on an MC9S12XS128MAL. Can someone point me in the right direction?

Thanks,

Re: Pass Port/Pin Address to Function

kef — Sat, 09 Jun 2012 13:59:29 GMT

Pins are not addresseable, but ports are, also pin masks are known. So you may have something like this

void setpin(char *port, char mask)

{

*port |= mask;

}

void clearpin(char *port, char mask)

{

*port &= ~mask;

}

setpin(PORTK, PORTK_PK1_MASK);

clearpin(PORTK, PORTK_PK1_MASK);

void setpin(char *port, char pinno)

{

*port |= (1<<pinno);

}

void clearpin(char *port, char mask)

{

*port &= ~(1<<pinno);

}

setpin(PORTK, 1);

clearpin(PORTK, 1);

etc.

Re: Pass Port/Pin Address to Function

Dustoor — Mon, 11 Jun 2012 23:36:09 GMT

Thank you. I've tried your suggestion, but I still get the following error:

Type mismatch (expected 'signed char *' , given 'unsigned char')

My function prototype is:

short _ReadEncoder(char *ssPort, char ssPinMask);

I am calling it as so:

motorPosition[0] = _ReadEncoder(PORTK, PORTK_PK0_MASK);

Re: Pass Port/Pin Address to Function

kef — Tue, 12 Jun 2012 00:00:53 GMT

My fault., & is missing. Should be

setpin(&PORTK, 1);

clearpin(&PORTK, 1);

Also you may need to change function argument from char *ssPort to unsigned char *ssPort.

motorPosition[0] = _ReadEncoder(&PORTK, PORTK_PK0_MASK);

Re: Pass Port/Pin Address to Function

Dustoor — Tue, 12 Jun 2012 09:29:42 GMT

Hi, thanks for your help once again. Placing a '&' and amending the function declaration allowed me to compile with no errors. However, when monitoring the pin using an oscilloscope, I found that it does not change when the function is called. Did we miss something?

Function declaration:

short _ReadEncoder(unsigned char *ssPort, char ssPinMask);

Function call:

motorPosition[0] = _ReadEncoder(&PORTK, PORTK_PK0_MASK);

P.S I'm sure the function is actually being called, since I am also calling a legacy function and seeing its result. I've also verified that the pin is initialized and tested it using the legacy function.

Re: Pass Port/Pin Address to Function

kef — Tue, 12 Jun 2012 11:47:16 GMT

It is not clear how is your function defined adn what you expect it to return.

Re: Pass Port/Pin Address to Function

Dustoor — Tue, 12 Jun 2012 21:46:22 GMT

Sorry, I just rechecked my function definition and found that I was setting it twice (rather than clearing first, waiting, then setting it back).

Thank you!