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Hello everyone!
I have been programming my MSP-EXP430FR4133 Launch Pad Development Kit using Code Composer Studio version 6.1.3.00034
My programs up to this point have been C code and they have been working great! I can compile them and download them onto the board and everything works as it should.
Recently I started learning assembly language and now I am seeing some very odd behavior that I cannot describe and I really need someone who has experience in this area to help me. This is NOT for a class project. I am a simple hobbyist who loves to tinker and right now I am at this dead end and could use some help.
The issue is that when I try to run a very simple assembly program to blink an LED on the board, nothing happens. That is not odd and I am sure we all have been there when your program doesnt do what it is supposed to do, right? But here comes the weird part. If I run a C program to do the same thing; turn on an LED; the C program will work just fine. If I then go back to my assembly program and try to run my assembly program again, it will work this time!! But if I shutdown and restart CCS and try to run my assembly program I again get the same output of having no LED turn on. What is going on?!
I have been reading all of these documents from TI and pouring over examples from the web and nothing can explain why my assembly program will only work if I first run a C program before I try to run my assembly program.
Here is the assembly program code:
;-------------------------------------------------------------------------------
; MSP430 Assembler Code Template for use with TI Code Composer Studio
;
;
;-------------------------------------------------------------------------------
.cdecls C,LIST,"msp430fr4133.h" ; Include device header file
;-------------------------------------------------------------------------------
.def RESET ; Export program entry-point to
; make it known to linker.
;-------------------------------------------------------------------------------
.text ; Assemble into program memory.
.retain ; Override ELF conditional linking
; and retain current section.
.retainrefs ; And retain any sections that have
; references to current section.
;-------------------------------------------------------------------------------
RESET mov.w #__STACK_END,SP ; Initialize stackpointer
StopWDT mov.w #WDTPW|WDTHOLD,&WDTCTL ; Stop watchdog timer
mov.b #00000001b, &P1OUT ; Load the P1OUT register so it turns on LED # 1 which is tied to bit 0 of the P1OUT register
mov.b #00000001b, &P1DIR ; Set the direction of the P1 register to be an output for bit 0 which is tied to LED 1
;-------------------------------------------------------------------------------
; Main loop here
;-------------------------------------------------------------------------------
InfLoop: jmp InfLoop
NOP
;-------------------------------------------------------------------------------
; Stack Pointer definition
;-------------------------------------------------------------------------------
.global __STACK_END
.sect .stack
;-------------------------------------------------------------------------------
; Interrupt Vectors
;-------------------------------------------------------------------------------
.sect ".reset" ; MSP430 RESET Vector
.short RESET
Now here is the C code that does the same thing:
#include <msp430fr4133.h>
int main(void)
{
PM5CTL0 &= ~LOCKLPM5; // Disable the GPIO power-on default high-impedance mode
// to activate previously configured port settings
WDTCTL = WDTPW | WDTHOLD; // Stop the watchdog timer
P1DIR = 0x01;
P1OUT = 0x01;
for(;;)
{
}
return (0);
}
Can anyone please help me understand why the assembly language project will only work if I first run the C program????
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