Thread: concerned about bogging down rc?
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Unread 30-01-2007, 09:36
Mike Bortfeldt Mike Bortfeldt is offline
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Re: concerned about bogging down rc?
Orborde,

Back in 2004/2005 I calculated the processor "free time" by counting the number of times the routine "Process_Data_From_Local_IO" was called in a 1 second period. Since this routine continually gets executed as long as there is nothing better to do (and we didn't have any custom code in it), it's a good way to see how loaded the processor is. In my case it took 14 instruction clock cycles to complete the while loop in "Main.c" as well as the call/addition/return of the "Process_Data_From_Local_IO" routine as long as there wasn't new OI data. With the processor running at 10 MHz instruction clock speed, it was a simple matter to calculate a % free time. We posted this to one of the User_Bytes so we could monitor it on the dashboard, and you could see the % free time change as the number of interrupts varied due to motor speeds (drive encoders mainly).

As for the 8% for the generate_pwms call, it sounds about right. My understanding is that the routine uses a loop to "wait" for the required amount of time to generate the 1-2 msec PWM pulse. Assuming a maximum 2 msec pulse, executed at about 38 times per second, that comes out to a delay of about 76 msec, or about 8% of the processor.

Mike