[fpc-devel] fpc on ARM without OS

[Bernd Mueller]

Florian Klaempfl wrote:
> Bernd Mueller schrieb:
>> Hello,
>>
>> I am trying hard to avoid C on an ARM7TDMI/ARMv4T Controller
>> (AT91SAM7Sx) ;-)
> 
> What about simply supporting the interrupt keyword on arm? Point me to
> some description and I'll implement it.

I searched the web for some details:

http://www.state-machine.com/arm/Building_bare-metal_ARM_with_GNU.pdf
    shows the complete interrupt mess on Page 6-1ff regarding gcc.

http://www.inf.ethz.ch/personal/wirth/Articles/Oberon/Interrupts.pdf
    Page 1 and 2.

http://www.mikrocontroller.net/topic/71979
    Last post from Martin Thomas.

and did not look further. I really think it is not worth your effort to 
implement this in fpc now. ARM interrupt handling is so complex, because 
of the different ARM modes and the different exception types (IRQ/Fast 
IRQ/SWI etc. which need different return address alignment). Another 
point are the vendor specific vector controller implementations. I think 
this would be very hard to implement, hard to debug and maybe error prone.

I could live with a performance penalty and think my second approach 
(going via the wrapper in the startup code) is perhaps the better start 
with fpc. This would have had the advantage too, that this should work 
with other controller vendors (ATMEL, ST, NXP, Samsung) without changing 
the compiler. Only the linker script and the startup code had to be adapted.

Regards, Bernd.