Since my old thread regarding this problem was filled with some off-topic-trash and never was answered, I'll try it again here:
I'm using the dmtimer-Example to toggle an output and to toggle a LED (this LED is of course switched only every 10000th..100000th call of ISR execution to see it blinking).
I'm using exactly the code from the BeagleBone example of Starterware except the serial interface output and timer start and reload count value. When I use values of 0xFFFFFE00 (equal to 21 usec) here, the ISR is called periodically as expected.
When I change the timer count/reload to 0xFFFFFF00 (equal to 10.6 usec) or higher values, the ISR is no longer called in expected way:
- ISR is called once more or less immediately (possibly after these 10.6 usec)
- then it is not called for several minutes
- then it is called periodically but according to frequency it seems the 32kHz clock is used instead of 24MHz CLK_M_OSC
My calculation is as follows: in 10.6 usec a CPU @1GHz can execute about 10000 clock cycles in ISR which should be more than enough for my little code, so this should not be a reason for stumbling about timing.
Is this calculation correct?
If not: there is an internal RAM/cache available that should be much faster - is it possible to move the ISR and all used variables into that RAM to execute the whole thing faster and to avoid timing problems?
All I want to do is to call a ISR with a frequency of 100 kHz (equal 10usec, equal timer value of 0xFFFFFF0F) which really should not be too fast for such a CPU?
Thanks!