ARm-C inter-networking

lpcware — Thu, 16 Jun 2016 00:52:01 GMT

Content originally posted in LPCWare by venkateshkuppan on Sun Apr 21 07:50:09 MST 2013
I am trying out a simple program for ARM-C inter-working. Here is the code:

#include<stdio.h>
#include<stdlib.h>

int Double(int a);
extern int Start(void);
int main(){

int result=0;
printf("in C main\n");
result=Start();
printf("result=%d\n",result);
return 0;
}

int Double(int a)
{
printf("inside double func_argument_value=%d\n",a);

return (a*2);
}
The assembly file goes as-

.syntax unified
    .cpu cortex-m3
    .thumb

    .align
    .global Start
    .global Double
    .thumb_func

Start:
      mov r10,lr
      mov r0,#42
      bl Double
      mov lr,r10
      mov r2,r0
      mov pc,lr

During debugging on LPC1769(embedded artists board), I get an hardfault error on the instruction " result=Start(). " I am trying to do an arm-C internetworking here. the lr value during the execution of the above the statement(result=Start()) is 0x0000029F, where the faulting instruction is,and the pc value is 0x0000029E. This is how I got the faulting instruction in r1

__asm("mrs r0,MSP\n"
"isb\n"
"ldr r1,[r0,#24]\n");

Can anybody please explain where I am going wrong? Any solution is appreciated. Thank you in advance.

Re: ARm-C inter-networking

lpcware — Thu, 16 Jun 2016 00:52:02 GMT

Content originally posted in LPCWare by whitecoe on Mon Apr 22 08:16:10 MST 2013
Lots of previous examples of calling assembler from C, and vice versa in the forum. Suggest you do a search for something like "C assembler" and browse a few for inspiration.

Note that using [FONT=Courier New][SIZE=2]MOV pc,lr[/SIZE][/FONT] as a function return is definitely not a good idea on Cortex-M class MCUs. Use [FONT=Courier New][SIZE=2]BX LR[/SIZE][/FONT] instead.

HTH!

LPCXpresso IDEのトピックARm-C inter-networking

ARm-C inter-networking

Re: ARm-C inter-networking