ZBasic Forum

Posted: **10 February 2008, 18:43 PM**

This code works just fine

#asm
	ldi     r18, 0x07 
	out     0x05, r18
#endasm

What I really want to do is use symbolic constants from GCC in the assembler code. The standard GCC code is something like:

Code: Select all

asm volatile&#40;"out %0, 0x07" &#58; "I" &#40;&#40;unsigned short&#41;&#40;PORTB&#41;&#41;&#58;&#41;;

That of course won't work in ZBasic. Can you confirm that this is the correct way of doing it:

Code: Select all

#asm
	ldi     r18, 0x07
	out     %0, r18 
	&#58; 
	&#58; "I" &#40;_SFR_IO_ADDR&#40;PORTB&#41;&#41;
	&#58; "r18"	
#endasm

It took a few attempts with generating the intermediate files to figure this all out.

Posted: **10 February 2008, 19:18 PM**

mikep wrote:Can you confirm that this is the correct way of doing it

It is indeed. Eventually, we'll need an application note describing the nuances of using inline C and assembly language. Since you're familiar with using avr-gcc, you likely already know everything that is necessary.

There currently isn't a good way to share constant values between ZBasic code and inline assembly code. One way to get the desired effect is to use a variable with a Constant attribute and an initial value.

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Private foo as Byte = &H55 Attribute&#40;Constant&#41;

Sub Main&#40;&#41;
  Debug.Print foo
#asm
   out     %0, %1
   &#58; 
   &#58; "I" &#40;_SFR_IO_ADDR&#40;PORTB&#41;&#41;, "r" &#40;zv_foo&#41;
#endasm
End Sub

I've given some thought to emitting ZBasic constants as #define preprocessor macros. That may be the best way to accomplish the desired effect.

ZBasic Forum

Using Assembler and C constants in ZBasic

Using Assembler and C constants in ZBasic

Re: Using Assembler and C constants in ZBasic