Lpc2000

Karl Olsen wrote:

> --- In lpc2000@yahoogroups.com, "friese99de" <jens.hildebrandt@e...> 
> wrote:
> 
>>Hi,
>>
>>I just came across this group because I have a problem similar to 
> 
> that
> 
>>of the OP. Did you find a solution meanwhile? 
>>I'm using gcc 3.2.1 under cygwin and tried to build the blinky_irq
>>example for a LPC2106. Since it didn't work I stripped the program
>>down to a bare endless loop in main() and a timer ISR that toggles a
>>LED an GPIO24. After approx. 3min. the LED stops toggling and I get 
> 
> an
> 
>>Abort exception. A look at the disassembled code showed that gcc is
>>messing up the stack pointer in IRQ mode, losing some words every 
> 
> time
> 
>>the ISR is invoked.
>> The code looks the following way:
>>
>>00000278 <tc0>:
>> 278:	e52dc004 	str	ip, [sp, -#4]!
>> 27c:	e1a0c00d 	mov	ip, sp
>> 280:	e24ee004 	sub	lr, lr, #4	; 0x4
>> 284:	e92dd80c 	stmdb	sp!, {r2, r3, fp, ip, lr, pc}
>> 288:	e24cb004 	sub	fp, ip, #4	; 0x4
>> 28c:	e3a0320e 	mov	r3, #-536870912	; 0xe0000000
>> 290:	e283390a 	add	r3, r3, #163840	; 0x28000
>> 294:	e5933000 	ldr	r3, [r3]
>> ... some load and store operations on GPIO registers with r2, 
> 
> r3 ...
> 
>> 2e0:	e3a02000 	mov	r2, #0	; 0x0
>> 2e4:	e5832000 	str	r2, [r3]
>> 2e8:	e95b980c 	ldmdb	fp, {r2, r3, fp, ip, pc}^
>>
>>As you can see, in the beginning registers are saved on the stack 
> 
> thus
> 
>>decrementing sp. BTW, the way ip is saved in the beginning is
>>pointless since ip is not restored from that location upon ISR exit.
>>At the end, registers are restored from stack using fp as base
>>pointer. The pc is loaded with the adjusted return address and
>>simultaneously cpsr is restored from spsr_irq. Sp however is not
>>restored so that at ISR exit sp is seven words lower than at ISR
>>entry.
>>Either I missed some point when building the program (e.g. forgot
>>certain gcc options) or gcc 3.2.1 is buggy here.
>>Options I use are  "-mcpu=arm7tdmi -gstabs" for the assembly of
>>startup.s and "-c -g -I. -mcpu=arm7tdmi" for compiling of C-source
>>files. Linker options are "-T Flash.ld -nostartfiles -Lgcc -L.", 
> 
> where
> 
>>Flash.ld is the linker script supplied with Keil's blinky_irq 
> 
> example
> 
>>adjusted to the actual Flash and RAM sizes of the LPC2106.
>>Has anybody else in the group encountered similar problems and if 
> 
> so,
> 
>>have you found a solution?
> 
> 
> The interrupt entry and exit code in gcc 3.2.x and older doesn't 
> work.  Either upgrade to gcc 3.3.x, where it works, or write the 
> entry/exit code yourself.
> 
> Regards,
> Karl Olsen
> 
> 
> 
>
>  
> 
> 

Hi Karl,

thanks for the clear answer. I just wanted to be sure that an upgrade of gcc 
wouldn't be in vain (at least with respect to my problem).

Regards,
Jens