FiXos is a project of kernel, targetting Casio's calculators in a first place, designed to be UNIX-like, even if full POSIX compatibility is not aimed.

As Casio's default OS on these platforms never switches to user mode, the kernel can be started like an Addin and deals directly with protected mode. A bootloader is included, and allows to run ELF files as a kernel (so this is not really a "bootloader", the real boot is in all case done by Casio's code for now).

The CPU primarly targeted is the SH3 7705 modified by Casio, used on fx9860, but other SuperH support may be added later. This CPU has a modern architecture, with priviligied/user modes, MMU for virtual memory and memory access control, cache, embedded USB device controller... All these things allow to have a modern kernel, with a good process isolation.

Finally, do not forget the goal is not to do an amazing kernel. I am working on that because it's fun, really interesting, and to do some proof-of-concept.

First of all : be sure about what you are doing before to start! This software is not a stable release of your favorite linux kernel. Any part of the program may cause damage to your machine, especially if you are using it on a not tested platform. Of course, I assure you I have never issued important problem when testing the kernel on my own calculator, but if for any reason this happens for you, you are warned.

To build the project, you must use a GCC toolchain configured for SuperH targets. In theory, the whole project use -nostdlib option when invoking GCC, so only binutils and compiler itself is needed. In addition, you must have a G1A Wrapper tool. Two tools exist : my own, C G1A Wrapper and the original version from Andreas Bertheussen, the fxSDK's G1A Wrapper which is better for icons but depends on Qt 4 SDK. Finaly, even if you can build everything manually, the project uses GNU make to be build.

If you are using make tool, please check and modify the values of Makefile variables for the different tool names and locations (in most case, only "global.mk" need to be changed, or in simplest case you can add option "TOOLCHAIN_PREFIX={prefix}" to make command). Check root Makefile for the kernel, bootloader/Makefile for the bootloader and user/Makefile for userspace things.

Once all is configured, simply execute :

make all

to build the kernel, bootloader and userland test programs. If everything works, to run the kernel using the bootloader, you will need to copy "bootloader/bootldr.g1a", "bootloader/bootldr.cfg", "fixos" and "user/test.elf" on the root of your calculator SMEM file system. Any shared library (*.so file) should be put in a directory named "LIB" located on the root of SMEM.

To run the kernel, start bootldr.g1a (its icon shows "FiXos"), and select the first loadable entry with [EXE].

Due to a bug into GNU ld 2.21 and earlier, please use a more recent version. The fixos.ld script was tested using binutils 2.22 (11/21/2011). If you have some troubles like "fixos.ld:xx cannot move location counter backwards" it's probably a ld problem.