How can I test RTX166 load? Is it possible to measure cpu busy rate?
No. Not without first defining what the difference between "busy" and "not busy" might be. The CPU doesn't really make such a distinction (unless you explicitly put it to sleep mode, that is).
Here is how I did it. I defined a task which would do only one thing: increment a counter. Then I defined a timer interrupt to work out fom the contents of the counter how long CPU spends executing this task. This would be "CPU idle time." Of course, this approach is not without problems. It steals time from other tasks, since RTX tiny is supposed to give all active tasks an equal share of CPU time. And it doesn't put CPU into low power mode. The good thing is, it gives you some idea about CPU utilization and helps find bootlenecks in the program which require optimization. - mike
In RTX166 Tiny, there is an IDLE task that you can modify to simply set a port pin low on entry and high on exit. Then, you can measure the duty cycle of that pin to figure out how much time the CPU is idle. Jon