Kinetis MicrocontrollersのトピックRe: KL03 Fast GPIO Registers

KL03 Fast GPIO Registers

ChristopherParn — Thu, 30 Apr 2015 21:11:50 GMT

Hello

I have started to used the fast GPIO registers on the KL03 but only seeing a marginal increase in I/O performance from 3.6MHz to 4MHz.

What performance increase should I be seeing?

How is the KL03 correctly setup to enable the faster I/O performance?

many thanks

Chris Parnell

Re: KL03 Fast GPIO Registers

egoodii — Fri, 01 May 2015 12:45:28 GMT

I expect the 'fast GPIO register' accesses are but a small part of your total instruction count. You MUST look very carefully at the assembly-code for ANY application needing speed-optimization., and understand the consequences of 'functions' and 'branches' in such a loop. Above all, you must maximize CPU register usage to avoid excess loads & stores.

Re: KL03 Fast GPIO Registers

mjbcswitzerland — Fri, 01 May 2015 19:24:47 GMT

Hi Chris

WIth 48MHz system clock, 24MHz bus clock and 24MHz flash clock (last one probably not relevant) the port output toggle rate using the normal GPIO is 8MHz

The same using the FGPIO is 24MHz.

The FPGIO accesses are 3x faster (1 output change per core clock, compared to 1 output change per 3 core clocks).

As Earl pointed out, it depends on your test SW since if it has additional instructions being executed the port accesses will only be a percentage of the overhead.

Regards

Mark

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