Teensy 3.2 RTC clock crystal

[ColdFire]

Hello,

My first post here, but I'm following since quite some time. I like this forum, very nice people here. Beside some Arduinos and clones I use a Teensy 3.6 since 2 months and ordered a 3.2.

Let me proceed to my question: For my new Teensy 3.2 I need to solder a clock crystal. I learned that there are different specs for the 32.768 kHz / 12.5 pF crystals showing either +-20 ppm or +-15 ppm. Would one notice the difference?

Thx,
Karl

 

[Frank B]

ppm means parts per million.
20 ppm are 0.0020 %, 15ppm are 0.0015%

If you notice the difference depends on you

Grüße nach Innsbruck.

 

[ColdFire]

Danke, Frank!

So, with a Teensy3Clock.compensate(+-40) I could adjust the crystal's stability to +-15ppm?

 

[Frank B]

I've never tried this, but in this forum are specialists who archieved much more. Maybe they read this...
As far as I know all crystals are very sensitive to temperature. That's all I can say

 

[manitou]

There are several threads in the teensy forums discussing RTC compensation, e.g.
https://forum.pjrc.com/threads/24563-Question-re-RTC-compensation-function

you might also search for rtc_compensate. As Frank notes, frequency is affected by temperature (and age and voltage ...)

 

[ColdFire]

Thx, I will do some research.

Karl

 

[manitou]

There are several threads in the teensy forums discussing RTC compensation, e.g.
https://forum.pjrc.com/threads/24563-Question-re-RTC-compensation-function
https://forum.pjrc.com/threads/18170-teensy-3-0-RTC-experiments?highlight=rtc_compensate

you might also search for rtc_compensate. As Frank notes, frequency is affected by temperature (and age and voltage and capacitance ...)

 

[ninja2]

üß

totally off topic ... but how did you type those special German characters, are they just keystrokes or a special keyboard?
tks

 

[Frank B]

A German keyboard

 

[ColdFire]

For instance, you can get the ü with 'Alt' and 252 on the numerical keyboard. By the way, my PC has an English keyboard for the sace of easier coding. The frequently used characters like [] {} are more convenient and quicker to type.

 

[ninja2]

I found the alt sequence for ß (alt-0223) which is all I need
großer Erfolg!
danke