Question about the CH_CFG_ST_FREQUENCY

[jonesrayan]

Thanks for the link, but i don't understand what the jitter really is ???. can you give me an example please to understand the problem of the jitter. please

[Giovanni]

It is random variation in timings.

Giovanni

[jonesrayan]

Can you give me more detail ?? can you give me an example

[tfAteba]

Hello Giovanni, JonesRayan,

As said Giovanni, a jitter is a random time that you generally dont want. It appear on your signal.

For Example, if you want to toggle a gpio pin to have a square signal with a period of 100us. You wouldn't have 100us all the time you measure. You will for example have 101us, 99us, 103us and so on.

Here is an image to illustrate my explanation.

I hope that help.

jitter.png (2.07 KiB) Viewed 4680 times

[tfAteba]

Here is a better illustration!

jitter2.png (2.71 KiB) Viewed 4680 times

[jonesrayan]

Merci, thanks
and how who cause this perturbation, how we avoid jitter or how we resolve this situation

[tfAteba]

Hi Jonesrayan,

and how who cause this perturbation

Jitter can be cased mainly by two case:
- External hardware (Bad electronic design).
- The software (Your program).

how we avoid jitter or how we resolve this situation

To try to avoid jitter, you have to:
- In case 1, respect some rules when you design your PCB( electronic circuit.).
- In the case 2: In my opinion, you have to take care of the CPU frequency of the micro-controller you are planing to use.
So that you don't use it in critical case. Giovanni already give you an example on a previous post viewtopic.php?p=26951#p26951.

I hope this will help and answers to your question.