> Our RTOS, which is available for all PICmicro devices, is also
> available in a freeware version called Salvo Lite. You may want to
> download it and take it for a spin. The Salvo User manual has a
> chapter dedicated to RTOS fundamentals -- not as in-depth as Jean
> Labrosse's book, but a good starting point, and free for the
> downloading.

The main problem with any RTOS running on 12 and 14 bit PICs (including
Salvo) is that a task switch can only occur in the main body of a task, not
in a called function. Think about the implications for a HD44780-LCD or I2C
library that has to wait between operations: it must either use a busy wait
(stalling the other tasks) or be in-lined in the main task (with grave
consequences for the code size). I think I must agree with Olin: no
accessible purpose stack? In that case an RTOS makes no sense. Note that a
library of usefull routines might still make sense (an Salvo seems to fall
in that category), but it is misleading to call it an RTOS. Note also that
the size of the microcontroller (RAM, ROM, interrupt or not) has nothing to
do with it. It is just the fact that you can not stack-switch.

Wouter van Ooijen

van Ooijen Technische Informatica: http://www.xs4all.nl/~wf/
Jal compiler for PIC microcontrollers:  http://www.xs4all.nl/~wf/wouter/jal

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