Hi Julien,

both ROM and RAM space are very tight now. To my knowlede disabling some unneeded modules or code is the only real cure if you really need the space, only some specific space issues can now be resolved manually.

Generally, a look at the C18 user guide and the Microchip forum is always worth while.

The "cannot fit" error need not be related to a ROM space issue, it depends on the section type. "idata" is meant for initialized variables, i.e. global and static variables with a compile time constant init value. This needs additional memory and can mostly be avoided by using an efficient init function and proper coding.

"udata" is for uninitialized globals and statics -- the compiler may switch the section itself if you mix initialized with uninitialized vars, take care to avoid that.

Normally a section can only hold up to 256 bytes, so you also need to take care about the size of your variables and arrange them manually into sections with remaining capacity -- the compiler will not optimize section layout by itself. That's the reason I noted all RAM struct usages in the comments and used two different sections already.

Function parameters are placed on the software stack, which is by default a fixed bank of 256 bytes. The stack does not overlay with data sections, so that should not be the source of problems unless you nest calls too deeply.

Another fixed section "tmpdata" is used for intermediate storage, this is stressed by complex calculations, and the compiler does not optimize these very well. So you may be better off breaking complex calculations down and using vars to keep intermediate results.

You may give the C18 "overlay" storage class and the currently unused optimizer options a try.

Good luck & tell us if you find a solution.

Regards,
Michael

Am 08.01.2015 um 17:28 schrieb Julien NOZAIS:

Hi everybody, best wishes for 2015.

I came across a memory limit while working on my project, I hope you could help me with it.
I am working on the vehicle_twizy.c file. So far I added about 300 lines of running code, and I started getting the compilation error "can not fit the section", which in general appears when you have too many modules enabled while compiling.

Error - section '.idata_net.o_i' can not fit the section. Section '.idata_net.o_i' length=0x00000035

I identified that the memory issue is happening as I add more code, and disappearing when I comment the code, independently of the nature of the code. I first resorted to switching to less memory intensive variables such as INT8.

I then tried to put as many of my variables as I could in a separate memory section. I used a pragma directive in the same fashion that is used for the battery monitoring system extension.

#pragma udata overlay vehicle_overlay_data2

It helped for a while, but at some point as I was writing calls to the writesdo(..) function a few times, it started again. I guess writesdo's arguments are stored in a memory section that was already at almost full capacity. I thought there would have been some margin before running into this kind of memory problem.

For now my workaround is to remove the battery monitoring from the compilation, as it leaves enough space for my code to run.

Do you have any comments or ideas on this ?

Best regards,

Julien
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