often not start oscillation MK10DN128VLH5

[daido]

The circuit is same as TWR-K20D50M

Resonator : CSTCE8M00G55-R0

Rf : 1 meg ohm

Cx : 18 pF

Cy : 18 pF

I am using __pe_initialize_hardware() of mqx\source\bsp\twrk20d50m\bsp_cm.c

It often do not start the oscillation.

What can I do ?

[john_suchyta]

A ceramic resonator with internal load caps does not require any external load caps. It just needs a feedback resistor. Do not add any internal capacitance in the MCU since the load caps are sufficient for oscillation.

Regards,

John

[soledad]

Hi,

MQX 4.2 doesn't support the MK10DN128VLH5 device so I assume you are cloning the twr-k20d50m bsp, is it correct??

If you are using the same clock configuration then you don't need to modify the bsp_cm.c file, however if you need made some modification then you need to follow the attached document, this document that explains how to change the default clock configurations.

Have a great day,
Sol

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[daido]

Hi Sol,

The oscillator curcuit of PK20DX128VFM5 in TWR-KM34Z50M is different from TWR-K20D50M's.

Is there any reason?

Minoru

[michael_galda]

Hi Minoru,

CSTCE8M00G55-R0 Reference manual / datasheet says, that the resonator, has a built in loading capacitance 33pF

CSTCE8M00G55-R0 pdf, CSTCE8M00G55-R0 description, CSTCE8M00G55-R0 datasheets, CSTCE8M00G55-R0 view :...

- Additional capacitive loading of the circuit may cause issues!

Moreover, if I am not mistaken the MCU supports the internal loading capacitors, they can be enabled in the SW.

And I guess, that there is also internal resistor inside the MCU

Please try to remove/depopulate the CAPs from the board.

And if the oscillator circuit is still unstable, check the SW settings as well. Oscillator High Gain mode (HGO=1) and the proper frequency range has to be selected in SW.

- I am the author of the TWR-KM34Z50M. I have copied the resonator components from other design. This resonator doesn't have internal loading caps, and the external capacitor values have been calculated for this resonator.

The main advantage was that the resonator component is available in small packages. - comparing to the crystals.

resonators are ususaly cheaper than precise crystals.

Anyway, there are disadvantages of the resonators:

1. (frequency deviation) The generated frequency is not so precise comparing to the crystals.

2. The frequency may vary from one component to other and with the enviromental influences.

- So for the precise timing, I would never use resonators again. And I would preffer crystal or canned osc.

Thanks,

Michael G.

[daido]

Hi Michael,

I removed caps.

Although never oscillated, I increase caps using OSC0_CR register.

12pF stable

14pF stable

16pF stable

18pF stable

20pF stable

22pF unstable

It might depend on the load caps...

regards

Minoru

[michael_galda]

It depends if the external ones + their stray parasitic capacitance are not > 20pF due external component tolerances.

Standard cheap caps are +/- 20% tolerance in precision.

Thanks,

Michael