get address of buffer to pointer !!

baycan vural

Intellectual 945 points

Other Parts Discussed in Thread: MSP430F6779

Hi,

I am using msp430f6779 mcu and I have code line like that:

unsigned char *inBuf_p ;

inBuf_p = channelPtr->Ports_p[portId].InBuf;

I am expecting to pass address of " channelPtr->Ports_p[portId].InBuf" this statement to "inBuf_p". I mean I want "InBuf" buffer to point " channelPtr->Ports_p[portId].InBuf" this statement address. But It points not address, it points value of " channelPtr->Ports_p[portId].InBuf". Am I doing wrong something ?

Best Regards

over 10 years ago

0 Leo Bosch over 10 years ago

Guru 23000 points

Yes, tell the linker it should be the address: inBuf_p = &channelPtr->Ports_p[portId].InBuf;

0 baycan vural over 10 years ago in reply to Leo Bosch

Intellectual 945 points

It has already told the linker. I am using a buffer name to do this.If you take look carefully you can see "InBuf"

0 Robert Cowsill over 10 years ago in reply to baycan vural

Guru 16361 points

What's the type of the InBuf member of Ports_p[n]? Is it a char*, char[] or something else?

0 baycan vural over 10 years ago in reply to Robert Cowsill

Intellectual 945 points

it is unsigned char*

0 Robert Cowsill over 10 years ago in reply to baycan vural

Guru 16361 points

Ok, so channelPtr->Ports_p[portId].InBuf is a pointer to a char (or array or chars) somewhere else in memory. When you do "inBuf_p = channelPtr->Ports_p[portId].InBuf", inBuf_p will point at the same char (or array of char) that channelPtr->Ports_p[portId].InBuf points at.

Is that what's happening when you test this?

0 baycan vural over 10 years ago in reply to Robert Cowsill

Intellectual 945 points

Yes.. and now I understand what are you trying to tell me. Yes, this is already expected process right?. Now I understand there is no problem here at all, my problem before this state. Am I right ?

0 Robert Cowsill over 10 years ago in reply to baycan vural

Guru 16361 points

That's right.

You'll need to use "&" if you want inBuf_p to point at [...].inBuf instead of at the buffer [...].inBuf points to. If you do that the type of inBuf_p needs to be unsigned char ** rather than unsigned char * too.

0 Leo Bosch over 10 years ago in reply to baycan vural

Guru 23000 points

Then you should create your question more carefully. If ‘InBuf’ is not specified I assume it’s just a variable, which fits with the observations you described.

You only told the linker to create a variable which must be able to store a pointer, not what will be the content or function of the variable it points to. If this is another pointer than you could do this with “unsigned char** inBuf_p;”.

Now evaluating the content of ‘inBuf_p’:

A = inBuf_p; will result in the content of ‘inBuf_p’ which is an address to another variable.

A = *inBuf_p; will result in the content of the variable which ‘inBuf_p’ points to.

0 baycan vural over 10 years ago in reply to Leo Bosch

Intellectual 945 points

Now I got it.. Thanks Leo

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get address of buffer to pointer !!