using external libraries

[schmurfy]

Hi,
I received my boards some days ago and currently playing with examples to learn how everything works, one application I wanted to try on this board is try porting part of libpHash to do images hash computation/comparaison on the epiphany to find duplicates in large sets (it also serves as a test project ) but I have some gray area I would need to fill first:

- how can I compile a library for use as part of an epiphany program ? more specifically a library with a configure script.
- I suppose the program loaded on the cores must be self contained so static compiling would be a requirement, right ?
- is there a limit on program size for the epiphany ? (the srec file if I got it right)

I read a lot both in the pdf docs and here on the forum but there is lot of thing to get right, any help/pointers on these would be much appreciated

[simoncook]

Hi schmurfy,

Using a normal configure script, you can specify --host=epiphany-elf to configure to specify that the library is to be built for an Epiphany core. Note you will probably want to also specify --prefix=/some/path to install it somewhere you can easily use it later after running "make install".

Yes, compiling the library statically is required, as there is no support for shared librarys on Epiphany as there is no filesystem to load the library from.

The only limit on program size is how large the memory where the program will be stored. Each Epiphany core has 32KB internally so if code is to sit within the core, the program can be no larger than that. If code will however live in shared DRAM, the linker script for that specifies 1MB as storage for each core, so the program will have to fit in that space.

Hope this helps.

[schmurfy]

thanks, that's really helpful !
About where the program is stored, how would you decide/control this ?
Does it switchs to DRAM automatically when the program is too big ?

[simoncook]

Where the program is stored is decided depending on which linker script you give to the compiler.

In the bsps/current directory in the eSDK directory you will find the three different linker scripts. You can pass the one you wish to use to the compiler via -Wl,-T,/path/to/fast.ldf when doing the final compilation for your Epiphany program.

[schmurfy]

Thanks, I am starting to understand how all this works.
That's quite an interesting beast we have

[Tylerlee12]

schmurfy, were you able to find a way to add your libraries in? We have 3 compiled .a files, but we can't seem to find a way to include them. Anyone have idea how to add these 3 files into the compilation process?

[simoncook]