andyzammy wrote: > I'm currently trying to use the INT0 to trigger
FIQ. It's the same
> problem as last time: I'm confused because i don't know what offset
to
> give the FIQ_Handler line in the startup file. I would have said #-0x134
> but that didn't work when i tried it.
FIQ is not vectored by VIC. Typically the FIQ handler is coded in
assembler starting right from the FIQ vector address. Otherwise the idea
of the FIQs may vanish.
Of course you can alternatively put a direct branch to your C function
into the FIQ vector address.
bump this up please, still not too sure about how this works
Reply by andyzammy●August 12, 20092009-08-12
I'm currently trying to use the INT0 to trigger FIQ. It's the same
problem as last time: I'm confused because i don't know what offset to
give the FIQ_Handler line in the startup file. I would have said #-0x134 but
that didn't work when i tried it.
Could someone please explain how this works?
Thanks for your time,
Zammy
Reply by Andy Zammy●April 21, 20092009-04-21
--- In l..., "rolf_meeser" wrote: >
> With this code you will end up in an infinite loop when an IRQ interrupt
occurs!
>
> Change the line containing
> LDR PC, IRQ_Addr
> to
> LDR PC, [PC, #-0x120]
>
> This will fetch the handler address from the VIC (VICAddress), and jump to the
handler all in one instruction.
>
> Rolf
wow, i've read those comments loads of times and not once did it ever hit
me. i can see now how the handlers branch to themselves. dow! i don't
really know any assembly so nothing is obvious to me at this point.
the interrupt now works, thanks very much for the fix Rolf, and thanks everyone
for their time and posts!
zammy
With this code you will end up in an infinite loop when an IRQ interrupt
occurs!
Change the line containing
LDR PC, IRQ_Addr
to
LDR PC, [PC, #-0x120]
This will fetch the handler address from the VIC (VICAddress), and jump to the
handler all in one instruction.
Rolf
Reply by Andy Zammy●April 21, 20092009-04-21
> In a previous post you said that your code is based
on an LPC2148 example.
>
> Did you take the whole project, and then modified it for the LPC2368?
> If yes, did you modify the LDR instruction in the startup code at address
0x18?
> The LPC2148 should have something like "LDR PC,[PC,#-0xFF0]", while for the
LPC2368 this should be "LDR PC,[PC,#-0x120]".
>
> Just an idea. This is a pretty common mistake...
>
> Rolf
I didn't use a startup file for the 2148, there was only the c code on that
site anyway (afaik), i used my own startup file. I have very little
understanding about startup and linker files, so there could be a problem in
there. I know that interrupts aren't enabled in my startup code, which is
why i needed the EnableIRQ functions with the assembly in it. Here is my startup
code, just in case anyone needs to look at it:
# *** Startup Code (executed after Reset) ***
# Standard definitions of Mode bits and Interrupt (I & F) flags in PSRs
.equ I_Bit, 0x80 /* when I bit is set, IRQ is disabled
*/
.equ F_Bit, 0x40 /* when F bit is set, FIQ is disabled
*/
# Stack Configuration
.equ Top_Stack, 0x40004000
.equ UND_Stack_Size, 0x00000004
.equ SVC_Stack_Size, 0x00000004
.equ ABT_Stack_Size, 0x00000004
.equ FIQ_Stack_Size, 0x00000004
.equ IRQ_Stack_Size, 0x00000080
.equ USR_Stack_Size, 0x00000400
# Starupt Code must be linked first at Address at which it expects to run.
.text
.arm
.global _startup
.func _startup
_startup:
# Exception Vectors
# Mapped to Address 0.
# Absolute addressing mode must be used.
# Dummy Handlers are implemented as infinite loops which can be modified.
Undef_Handler: B Undef_Handler
SWI_Handler: B SWI_Handler
PAbt_Handler: B PAbt_Handler
DAbt_Handler: B DAbt_Handler
IRQ_Handler: B IRQ_Handler
FIQ_Handler: B FIQ_Handler
# Reset Handler
Reset_Handler:
# Initialise Interrupt System
# ...
# Setup Stack for each mode
LDR R0, =Top_Stack
# Enter Undefined Instruction Mode and set its Stack Pointer
MSR CPSR_c, #Mode_UND|I_Bit|F_Bit
MOV SP, R0
SUB R0, R0, #UND_Stack_Size
# Enter Abort Mode and set its Stack Pointer
MSR CPSR_c, #Mode_ABT|I_Bit|F_Bit
MOV SP, R0
SUB R0, R0, #ABT_Stack_Size
# Enter FIQ Mode and set its Stack Pointer
MSR CPSR_c, #Mode_FIQ|I_Bit|F_Bit
MOV SP, R0
SUB R0, R0, #FIQ_Stack_Size
# Enter IRQ Mode and set its Stack Pointer
MSR CPSR_c, #Mode_IRQ|I_Bit|F_Bit
MOV SP, R0
SUB R0, R0, #IRQ_Stack_Size
# Enter Supervisor Mode and set its Stack Pointer
MSR CPSR_c, #Mode_SVC|I_Bit|F_Bit
MOV SP, R0
SUB R0, R0, #SVC_Stack_Size
# Enter User Mode and set its Stack Pointer
MSR CPSR_c, #Mode_USR
MOV SP, R0
# Setup a default Stack Limit (when compiled with "-mapcs-stack-check")
SUB SL, SP, #USR_Stack_Size
# Relocate .data section (Copy from ROM to RAM)
LDR R1, =_etext
LDR R2, =_data
LDR R3, =_edata
LoopRel: CMP R2, R3
LDRLO R0, [R1], #4
STRLO R0, [R2], #4
BLO LoopRel
# Clear .bss section (Zero init)
MOV R0, #0
LDR R1, =__bss_start__
LDR R2, =__bss_end__
LoopZI: CMP R1, R2
STRLO R0, [R1], #4
BLO LoopZI
# Enter the C code
ADR LR, __main_exit
LDR R0, =main
BX R0
__main_exit: B __main_exit
.size _startup, . - _startup
.endfunc
.end
Reply by rolf_meeser●April 21, 20092009-04-21
--- In l..., Andy Zammy wrote:
> > What's the size of your IRQ stack? I bet
it's too small, so
> > overflows into your System/User stack, trashing it.
>
> the IRQ stack is currently 0x80. i tried making it bigger but it didn't
seem to make any difference.
In a previous post you said that your code is based on an LPC2148 example.
Did you take the whole project, and then modified it for the LPC2368?
If yes, did you modify the LDR instruction in the startup code at address
0x18?
The LPC2148 should have something like "LDR PC,[PC,#-0xFF0]", while for the
LPC2368 this should be "LDR PC,[PC,#-0x120]".
Just an idea. This is a pretty common mistake...
Rolf
Reply by Andy Zammy●April 21, 20092009-04-21
--- In l..., "mjames_doveridge" wrote:
> Well, what happens when you put a debugger breakpoint
at the start of the interrupt handler?
>
> There are those in this group that maintain that they can get these complex,
embedded systems working without a debugger, but I really do not see how,
especially with interrupts and possibly an OS .
>
> Rgds,
> Martin
Unfortunately i do not have access to a jtag debugger and i doubt i will be able
to get a hold of one. I will look into it though.
--- In l..., Jan Brittenson wrote:
> What's the size of your IRQ stack? I bet
it's too small, so
> overflows into your System/User stack, trashing it.
the IRQ stack is currently 0x80. i tried making it bigger but it didn't
seem to make any difference.
Reply by Jan Brittenson●April 20, 20092009-04-20
Andy Zammy wrote: > bump. i still haven't been able to get anywhere
with this. any suggestions would be really appreciated. What's the size of your IRQ stack? I bet it's too small, so
overflows into your System/User stack, trashing it.
Reply by mjames_doveridge●April 20, 20092009-04-20
--- In l..., Andy Zammy wrote: >
> bump. i still haven't been able to get anywhere with this. any
suggestions would be really appreciated.
>
Well, what happens when you put a debugger breakpoint at the start of the
interrupt handler?
There are those in this group that maintain that they can get these complex,
embedded systems working without a debugger, but I really do not see how,
especially with interrupts and possibly an OS .
