Didn't get much actually done today. I mostly fought with GCC and Binutils. Specifically, the linker and linker scripts and trying to compile with -nostdlib. I may skip this bit for now and come back to it as the stdlib works for now.

I seem to be unable to find the documentation regarding interrupts (especially with regard to the generated assembly.) I decided to write a quick C test to figure out what it's expecting. It's interesting, but not surprising, the old toolchain and new toolchain produce interrupts differently.

#include <msp430.h>
#define t_int(i) void __interrupt(i) test_##i() {}
t_int(TRAPINT_VECTOR)
t_int(PORT1_VECTOR)
t_int(PORT2_VECTOR)
t_int(ADC10_VECTOR)
t_int(USCIAB0TX_VECTOR)
t_int(USCIAB0RX_VECTOR)
t_int(TIMER0_A1_VECTOR)
t_int(TIMER0_A0_VECTOR)
t_int(WDT_VECTOR)
t_int(COMPARATORA_VECTOR)
t_int(TIMER1_A1_VECTOR)
t_int(TIMER1_A0_VECTOR)
t_int(NMI_VECTOR)
t_int(RESET_VECTOR)

compiled with:

msp430-elf-gcc -I$MSPGCC/include -mmcu=msp430g2553 -S test_inter.c

It results in (just a snippet):

        .balign 2
        .global test_TIMER0_A0_VECTOR
        .section        __interrupt_vector_10,"ax",@progbits
        .word   test_TIMER0_A0_VECTOR
        .text
test_TIMER0_A0_VECTOR:
; start of function
; attributes: interrupt 
; framesize_regs:     0
; framesize_locals:   0
; framesize_outgoing: 0
; framesize:          0
; elim ap -> fp       2
; elim fp -> sp       0
; saved regs:(none)
        ; start of prologue
        ; end of prologue
        ; start of epilogue
        RETI
        .size   test_TIMER0_A0_VECTOR, .-test_TIMER0_A0_VECTOR

A similar macro

#define t_int(i) void __attribute__((interrupt(i))) test_##i() {}

for the old toolchain produced:

        .p2align 1,0
.global test_TIMER0_A0_VECTOR
        .type   test_TIMER0_A0_VECTOR,@function
/***********************
 * Interrupt Vector 9 Service Routine `test_TIMER0_A0_VECTOR' 
 ***********************/
test_TIMER0_A0_VECTOR:
.global __isr_9
__isr_9:
        push    r4
        mov     r1, r4
        add     #2, r4
        pop     r4
        reti
.Lfe7:
        .size   test_TIMER0_A0_VECTOR,.Lfe7-test_TIMER0_A0_VECTOR
;; End of function

It's interesting that the new toolchain puts the interrupt in a different section, while the old toolchain has a predefined global that, I'm assuming, the linker knows to look for. Not sure which one I like, but both feel relatively under documented.

Today is my 15th day in a row. I think I'm more proud of that than what I was able to accomplish today.

I didn't get nearly as much as I would have liked to done. I started reading the documentation for USCI UART in the User's Guide, I started to look at how MSPGCC generates interrupts in assembly. At about that time, I realized I'm not yet using the upstream Ti MSP430 GCC. I ended up downloading that, and fixing my code to compile with that toolchain, which was trivially adding a couple ampersands in front of some constants. It was actually more work to edit the Makefile to work out the MSP430 GCC toolchain directory. I find it slightly inconvenient to need to tell msp430-elf-gcc where to include standard headers from. Overall, I think the new toolchain is the right switch going forward.