KL05 low power mode

[francopaggio]

Hello,

I'm starting working with KL05 (not on FRDM-KL05 board) and I'm trying to find a low power mode suitable for my specs.

My goal is to achieve 500uA running with an instruction clock of about 2MHz. (active peripherals are one UART rx-only and two timers).

(my actual application based on MC9S08 runs for 10% of time and 90% sleeps in wait condition).

Is it better to use an external crystal/resonator or internal clock to reduce consumption?

Could you suggest me any literature about kinetis low power modes and if possible source code to switch among the MCG modes?

Is there a way to check if instruction clock is the desired one?

Another question: in my project I add the "BitIO" component to drive an output pin, but running at 20.97152 MHz and using "SetVal/ClrVal" functions, it takes 1,2us to set or reset the pin (20us @ 1.31072MHz core clock). So long execution times force my main loop to spend a lot of processing time increasing consumption. --> are available lower level functions? (not only for pin management, but in general for all peripherals).

Thanks in advance,

Franco

[Monica]

Hello Franco!

How is the project going? Was this helpful? Keep us posted! :smileywink:

Best regards,

Monica.

[francopaggio]

Hello all,

thanks for your suggestion. I'm still trying to find the best operating mode to achieve a compromise between consumption and performance.

Is available any source code with functions to switch among the MCG modes of operation?

Thanks in advance,

Franco

[adriansc · Accepted solution]

Hi,

First of all I recommend you to take a look at Kinetis L Peripheral Module Quick Reference document (KLQRUG)

http://cache.freescale.com/files/32bit/doc/quick_ref_guide/KLQRUG.pdf  specially Chapter 4: Clocking System.

FLL Engaged Internal (FEI) mode for MCG is controlled by Internal Clock. This mode is the lowest consumption mode but maybe is not the best one for your application. Check the KL05 Sub-Family Reference Manual in section MCG modes of operation. http://cache.freescale.com/files/32bit/doc/ref_manual/KL05P48M48SF1RM.pdf?fsrch=1&WT_TYPE=Reference%...

According to your last question PEx (Processor Expert) functions normally spend more time than functions in a bare board project without this development system.

Hope this helps.