topic Re: How much time will MKL16 take when Check IO high input？ in Kinetis Microcontrollers

How much time will MKL16 take when Check IO high input？

jiannianli — Sun, 13 Sep 2020 02:50:47 GMT

Hi ，

I need to wait PTD4 to high ,and then use timer to do something .

follows is my code :

TestIO_00; // Set Test IO low

//other codes

while((GPIOD_PDIR&0x00000010)==0){}; //wait the PTD4 to High ， this code will take different //time, and this is my question

TestIO_11; // Set Test IO High

//other codes

I found that when the PTD4 turn to high , the MKL16 take different time to check . Now the CoreClock is 2MHz , BusClock is 1MHz .

folows are my two records ,and you can find that the time of check PTD4 high is not same . So, how to make the check time same ?

Re: How much time will MKL16 take when Check IO high input？

jiannianli — Sun, 13 Sep 2020 02:54:40 GMT

the record picture are:

Re: How much time will MKL16 take when Check IO high input？

Anonymous — Sun, 13 Sep 2020 03:24:30 GMT

Hi,

Above two images show same time difference Bx-Ax = 960 ns. Please refer data sheet section 2.3.2 General switching specifications for GPIO operation time.

Thanks

Kalaimani Arumugam

Re: How much time will MKL16 take when Check IO high input？

jiannianli — Sun, 13 Sep 2020 03:54:02 GMT

Hi Kalaimani ,

thanks for you reply.

the two picture show that Bx-Ax=9.6 us . I had make a new test pitcure ( put the two test into one picture ) . you can find that the different time is 1.88us ,and is too large for our project now.

Re: How much time will MKL16 take when Check IO high input？

kerryzhou — Mon, 14 Sep 2020 06:29:07 GMT

Hi jiannianli,

You can use the FGPIO to control the GPIO output and the read the input, or use the interrupt to read the PTD4 input, it will be more quick than your polling mode.

In fact, even you just toggle the GPIO output, it will also need the times, FGPIO toggle frequency can reach to the core clock /2.

Your test result time in fact include two part, detect the PTD4 time, and the GPIO output time. Obout the test IO output time, you can toggle it directly in the code and test it, then use your orginal test time minus the GPIO output time, it is your PTD4 detect time.

Wish it helps you!

If you still have questions about it, please kindly let me know!

Best Regards,

Kerry

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Re: How much time will MKL16 take when Check IO high input？

jiannianli — Mon, 14 Sep 2020 07:06:49 GMT

Hi Kerry,

thanks for your reply ,and maybe I know how to do . than you.

Re: How much time will MKL16 take when Check IO high input？

kerryzhou — Tue, 15 Sep 2020 02:56:08 GMT

Hi jiannianli,

You are welcome!

If you have any new questions in the future, welcome to create the new question post. \

Best Regards,

Kerry