> I'm trying to get a frontend running on an arduino yun single board computer
> (cpu is Atheros AR9331 and OS is a linux derivate
> http://arduino.cc/en/Main/ArduinoBoardYun )

What you want to do should be possible.

Here, the smallest machine we used to run a MIDAS frontend was a 300MHz PowerPC processor inside a 
Virtex4 FPGA with 256 Mbytes of RAM. Looks like your machine is a 400MHz MIPS with 64 Mbytes of RAM 
so there should be enough hardware available to run a MIDAS frontend underLinux.

One source of trouble could be if your MIPS CPU is running in big-endian mode (MIPS can do either big-
endian or little-endian). MIDAS supports big-endian frontends connecting to little-endian x86 PC hosts, 
but with big-endian machines getting less common, this code does not get much testing. If you run into 
trouble with this, please let us know and we will fix it for you.

> The idea is to use this device for some slow control for our experiment (ASACUSA
> Antihydrogen) we are using midas as main DAQ system and we would like to
> integrate the slow control with this small boards.

> My question is: How can I compile the midas library with the openwrt crosscompiler?

In the MIDAS Makefile, looks for the "crosscompile" target which we use to cross-build MIDAS for our 
PowerPC target using the regular GCC cross compiler chain. If you have very new MIDAS, you will also see 
some make targets for ARM Linux machines, also using GCC cross compilers.

> the system discspace is very limited (6 MB) therefore I don't want to have mysql, zlib an so on.

The MIDAS Makefile crosscompiler builds a very minimalistic version of MIDAS - no mysql, no sqlite, etc 
requirements for the MIDAS libraries and frontend. zlib may be required but it is not used by frontend 
code, so you may try to disable it.

If that is still too big, there is a possibility for building a super-minimal version of MIDAS just for running 
cross-compiled frontends. We use this function to build MIDAS for VxWorks. If you want to try that, I 
think it is not in the main Makefile, but in the VxWorks Makefile. Let me know if you want this and I can 
probable restore this function into the main Makefile fairly quickly.

> Do you have any suggestions on how to realize something like that?

1) cross compile MIDAS (see  the Makefile "make crosscompile" target)
2) cross compile your frontend
3) run it, with luck, it will fit into your 64 Mbytes of RAM

If you run into problems, please post them here (so other people can see the problems and the solutions)

K.O.