Mixing c & assembly in Keil IDE

[lakshman]

Dear Nordic, Whats wrong with the below code. It works well in RFduino but when I try to port the same code in Keil environment.Its not working throwing error as 1.identifier "asm is undefined 2. expected a ";" code below

void mixC_and_Assembly()
{
 volatile uint32_t  *out = &NRF_GPIO->OUT;
 byte *_ptbytes = txBuf;
 byte *_ptbytes1 = &txBuf[32];
 uint32_t  rbyte;

   // out =%0
   //_ptbytes = %1
   //rbyte = %2
  asm  volatile
  ( 
       //"headSP:\n\t"
       "push {r0,r1,r2,r3}\n\t"
       
        "ldrb %2, [%1,#0]\n\t"    //    rbyte = *_ptbytes
        "str %2,[%0,#0] \n\t"    //  *out = _ptbytes[0]

        "ldrb %2,[%1,#1] \n\t"    //  rbyte = *_ptbytes
        "str %2,[%0,#0] \n\t"    //  *out = _ptbytes[1]
       
        "ldrb %2,[%1,#2] \n\t"    //  rbyte = *_ptbytes
        "str %2,[%0,#0] \n\t"    //  *out = _ptbytes[2]

        ......
        .....
        .....
        ......
        
        
        "pop {r0,r1,r2,r3} \n\t" 
    ::
    "r" (out),   // %0
    "r" (_ptbytes),   // %1
    "r" (rbyte), //%2
    "r" (_ptbytes1)   // %3
    :"memory"
  );
}

after going through core_cmo.h file I have changed asm into __asm

void mixC_and_Assembly()
{
 volatile uint32_t  *out = &NRF_GPIO->OUT;
 byte *_ptbytes = txBuf;
 byte *_ptbytes1 = &txBuf[32];
 uint32_t  rbyte;

   // out =%0
   //_ptbytes = %1
   //rbyte = %2

  __asm  volatile
  ( 
       //"headSP:\n\t"
       "push {r0,r1,r2,r3}\n\t"
       
        "ldrb %2, [%1,#0]\n\t"    //    rbyte = *_ptbytes
        "str %2,[%0,#0] \n\t"    //  *out = _ptbytes[0]

        "ldrb %2,[%1,#1] \n\t"    //  rbyte = *_ptbytes
        "str %2,[%0,#0] \n\t"    //  *out = _ptbytes[1]
       
        "ldrb %2,[%1,#2] \n\t"    //  rbyte = *_ptbytes
        "str %2,[%0,#0] \n\t"    //  *out = _ptbytes[2]

        ......
        .....
        .....
        ......
        
        
        "pop {r0,r1,r2,r3} \n\t" 
    ::
    "r" (out),   // %0
    "r" (_ptbytes),   // %1
    "r" (rbyte), //%2
    "r" (_ptbytes1)   // %3
    :"memory"
  );
}

still I am getting error as "expected ")" ". is there anything I need to add in compiler option in keil ? kindly advise Thanks and Regards Lakshman,PMP,PMI-RMP

[Hung Bui]

Hi Lakshman,

You can find an example of using ASM with C in KEIL in the bootloader_util.c for the bootloader project in our SDK. You can find the file in \components\libraries\bootloader_dfu

[Vidar Berg]

Just like to add that the asm syntax is not the same for Keil and the GNU arm toolchain. bootloader_util.c shows the difference as Hung pointed out (SDK v8.1.0+).

[lakshman]

Hi Hung & Vidar, Thanks for your response.Yes I went through still I am unable to use it in proper way. After browsing I found out that above asm code is for GNU compiler. For Keil its very easy you can just give the variable name "as is" like below

void mixC_and_Assembly()
{
 volatile uint32_t  *out = &NRF_GPIO->OUT;
 byte *_ptbytes = txBuf;
 byte *_ptbytes1 = &txBuf[32];
 uint32_t  rbyte;

   // out =%0
   //_ptbytes = %1
   //rbyte = %2

__asm  volatile
		{      
	        LDRB rbyte,[_ptbytes,#0]    //    rbyte = *_ptbytes
	        STR  rbyte,[out,#0]    //  *out = _ptbytes[0]
	
	        LDRB rbyte,[_ptbytes,#1]    //  rbyte = *_ptbytes
	        STR  rbyte,[out,#0]         //  *out = _ptbytes[1]
	   
	        LDRB rbyte,[_ptbytes,#2]    //  rbyte = *_ptbytes
	        STR  rbyte,[out,#0]         //  *out = _ptbytes[2]
	     
	        LDRB rbyte,[_ptbytes,#3]    //  rbyte = *_ptbytes
	        STR  rbyte,[out,#0]         //  *out = _ptbytes[3]
	
	 	    LDRB rbyte,[_ptbytes,#4]    //  rbyte = *_ptbytes
	        STR  rbyte,[out,#0]      
	        ......
	        .....
	        .....
	        ......
	
	        LDRB rbyte,[_ptbytes1,#16]           //  rbyte = *_ptbytes1
	        STR  rbyte,[out,#0]             //  *out = _ptbytes1[16]
	 
	        LDRB rbyte,[_ptbytes1,#17]           //  rbyte = *_ptbytes1
	        STR  rbyte,[out,#0]             //  *out = _ptbytes1[17]
      
		}
}

I am using p0.2,p0.3and p0.4 .If I give use the assembly I am able to get expected result but all the led is ON. volatile uint32_t *out = &NRF_GPIO->OUT; with the above statement I write to P0.2,P0.3 & P0.4 at the same time. will it have any effect on LED ? did I miss anything.?

Thanks and Regards Lakshman,PMP,PMI-RMP

[Hung Bui]

Hi Lakshman,

I'm sorry that I don't really understand the code . You write to NRF_GPIO->OUT 18 times ?

Note that NRF_GPIO->OUT; is a 32 bit register and each bit control one pin. Each write to it will update the value of all 32 pins. You can also use NRF_GPIO->OUTSET NRF_GPIO->OUTCLR to set/clear one or multiple pins without affecting the other pin.

[lakshman]

Hi HungBui, Yes I wrote NRF_GPIO->OUT more than 18 times. yes I am aware it will update all 32 pins. I want to control 5 pins at the same cycle. if you use NRF_GPIO->OUTSET NRF_GPIO->OUTCLR to set/clear one or multiple pins you will be controlling one pin at a time. Moreover I am using STRB rbyte ,[out,#0] so only 8 pins will get affected if it is output pin.

Thanks and Regards Lakshman,PMP,PMI-RMP