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TMS320F28P650DH: Generic questions about MIPS you need and CPU usage rate in system

Johnny Chen
Expert 4990 points
Part Number: TMS320F28P650DH


Tool/software:

Hi Champ,

I am asking for my customer.

(1). Before getting more details about user's application and system such as the communications involved at what frequency, and what kind of processing is done in their control loop, etc., is the a generic way to preliminary assess at least how many MIPS you need, to determine whether you need dual CPUs or not and additional CLA for designing system ? 

(2). Any generic way to know current CPU usage (MIPS) across the system ? 

Could I assess by GPIO toggling in the fastest ISR, or within the fastest few ISRs, and see them together.

For example: 50 KHz (20us) ISR uses 10us,10 KHz (100 us) ISR uses 5 us. So, I can reasonably launch around every 20 us, it runs 10+5/1 = 11 us since the fastest one or the first few ISRs are the most critical. Therefore, I could get the CPU utilization is about 11 us / 20 us = 55%. 

Does the assessment look reasonable from the expert ?

Thanks and regards,

Johnny

  • 0
    TI__Mastermind 38240 points

    Hi Johnny,

    There is no straightforward way to benchmark the code but there are steps you can take to approximate CPU usage.  First, as you described involves using GPIOs but when it comes to fast control loop execution, GPIO toggling command would take up some time.  There are code profiling examples in C200Ware that employ the ERAD module.  These examples can be found in folder f28p65x/examples/c28x/erad/application_owned_examples.  Look for the examples with profile in the test name.  Once customer gets an idea on how long the code execution takes, customer can then decide if a second CPU, or CLA is needed.  There are also some ode optimizations that customer can use.  I can point you to our SW team if additional information is needed.

    Regards,

    Joseph