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

Jean-Pierre Desrochers jpdesroc at oricom.ca
Thu Aug 12 02:33:45 CEST 2021


> 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.

That’s exactly what I had coded before the hardware ‘solution’.

Polling the 3 encoder pins.  Everything was working fine until I added some
code to process the encoder changes. Then BOOM..
Many missed counts everywhere (increments/decrements).
The interrupt style was even harder to implement since there were
4 different states to read before any final counts.
A $2 bucks chips solution makes me spend my  time
elsewhere in my  project releasing.
Again..

Any simple, fast and reliable interrupt driven code to suggest ??

Managing all the encoder 4 steps with debouncing too ?

 

 

De : Synth-diy [mailto:synth-diy-bounces at synth-diy.org] De la part de Jay
Schwichtenberg via Synth-diy
Envoyé : 11 août 2021 20:14
À : synth-diy at synth-diy.org
Objet : Re: [sdiy] Rotary encoder reading.. hardware solution (fast &
accurate)

 

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> 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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