[sdiy] Rotary encoder reading.. hardware solution (fast & accurate)

Jay Schwichtenberg jschwich53 at comcast.net
Thu Aug 12 02:13:31 CEST 2021


I agree with Tom, this is a trivial uC problem that can be solved with 
about a page of firmware.

Don't know where there is any code out there for this. Might check out 
in Arduino land or MicroChip.

I can think of 4-6 ways of doing this, depends on what else the uC needs 
to do.

Typically I'd use a 1 ms timer to poll the switch and run a state 
machine. State machine would look for the encoder changing, start a 
count down timer for debouncing, when timer is 0 read encoder and 
compare it to last stable value to see if it has changed.

Jay S.


On 8/11/2021 3:53 PM, Jean-Pierre Desrochers wrote:
>
> _Any simple_, fast and reliable interrupt driven code to suggest ??
>
> Managing all the encoder 4 steps with debouncing too ?
>
> *De :*Tom Wiltshire [mailto:tom at electricdruid.net]
> *Envoyé :* 11 août 2021 18:38
> *À :* Jean-Pierre Desrochers
> *Cc :* SDIY
> *Objet :* Re: [sdiy] Rotary encoder reading.. hardware solution (fast 
> & accurate)
>
> Gagh! Two whole chips to save writing a few lines of code! Heresy! ;)
>
> Tom
>
>
>
> On 11 Aug 2021, at 21:27, Jean-Pierre Desrochers <jpdesroc at oricom.ca 
> <mailto:jpdesroc at oricom.ca>> wrote:
>
> For anybody who could be interested..
>
> Just found this video yesterday and tried the circuit..
>
> https://www.youtube.com/watch?v=UlehqasO-fo&t=1471s 
> <https://www.youtube.com/watch?v=UlehqasO-fo&t=1471s>
>
> Outputs A and B (CD4013) connected to PORTB of a PIC16F1783
>
> (RB0 and RB1) using interrupts on change (rising edges).
>
> Now I only have to check one incoming pulse on each RB0 & RB1
>
> to increment or decrement a counter.
> Much faster than computing  all the 4 possible states in each encoder step
> to finally get a result.
>
> My interrupt uses TIMER1 (1msec steps), RB0 & RB1 on change.
>
> No missing counts anymore even rotating fast, on both direction.
>
> <image001.jpg>
>
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