On Fri, May 4, 2012 at 2:38 PM, Adam Ford <adam.f...@braemarinc.com> wrote:
> We have an older project at my work where we use the TI BSL loaded to
> load code over RS-232. Our code is broken up into two categories a
> configuration file and a firmware file and they are both loaded together.
>
> The configuration file is a list of constants stored in flash and
> specific addresses and they are unique for each of our customers, but
> the firmware file is the same.
>
> The code we have now was written with IAR, and I'm trying to port it
> over to mspgcc.
>
> What I'd like to be able to do is compile the firmware with the linker
> script specifying certain addresses of data, but I don't want the
> compiler to actually put any data at those locations.
>
> For the configuration, I'd like to just compile the constant variables
> without firmware.
>
> The problem I see is that GCC initializes the constant variables in the
> FW which I have to go and manually delete because those constants are
> loaded from a separate txt file. I'd like to have that more streamlined
> technique to build both. Any ideas on the best way to do that?
If the variables have no initializer in the source, the firmware image
shouldn't include data that gets written to their location. However, in
that case they will normally be assigned to the .bss section, and will be
zeroed in the startup code.
If you want to specify the actual address in a linker script, place the
variable declarations in the .noinit section using a section attribute.
That should be safe: I'd have to play around to see if it's necessary; it
may be that with a specific address the linker won't accrue the object sizes
to the data size or bss size.
An alternative that avoids the linker script is to use an asm statement so
there's no symbol used at all: everything is relative to the fixed address.
Play with the example below.
#include <stdio.h>
__attribute__((section(".noinit")))
const char client_id[20]
//__asm__("0x8000")
;
__attribute__((section(".noinit")))
char mutable_client_data[32]
//__asm__("0x3000")
;
struct client_data_t {
int n1;
int n2;
} client_data __asm__("0x3100");
int putchar (int c) { return c;}
int main ()
{
printf("Client %d.%d %s, mutable %s\n", client_data.n1,
client_data.n2, client_id, mutable_client_data);
}
> thanks
>
> adam
>
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Please note: http://www.spinics.net/lists/gcchelp/msg16825.html and
http://gcc.gnu.org/lists.html#policies
mspgcc-users doesn't currently follow this, though it would apply if
msp430 support is integrated into GCC upstream.
Peter
>
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