I have searched far in the forum and I haven seen much about eCos, I have been working long in RTLinux, uLinux , and in eCos.
Still eCos have been the "SMALLEST" of all them and for me has worked prety well.
eCos is royalty free, released under GPL and has very good suport under cygwin(the same people did cygwin), for the windows users, even there's a Insight for every cross-compiler.
It's ported tor:
ARM, Hitachi H8300, Intel x86, MIPS, Matsushita AM3x, Motorola 68k, PowerPC, SuperH, SPARC and NEC V8xx
And the following core functionality is provided:
* Hardware Abstraction Layer (HAL)
* Real-time kernel
o Interrupt handling
o Exception handling
o Choice of schedulers
o Thread support
o Rich set of synchronization primitives
o Timers, counters and alarms
o Choice of memory allocators
o Debug and instrumentation support
* µITRON 3.0 compatible API
* POSIX compatible API
* ISO C and math libraries
* Serial, ethernet, wallclock and watchdog device drivers
* USB slave support
* TCP/IP networking stacks
* GDB debug support
Yo can found it at: **broken link removed**