[sdiy] Inifinity encoders

[Csaba Zvekan]

On Jul 9, 2008, at 1:12 AM, Samppa Tolvanen wrote:

> Hi again,
>
> On Wed, Jul 9, 2008 at 1:31 AM, Csaba Zvekan <czvekan at gmail.com>  
> wrote:
>
>>>
>>> I connect my encoders to shift registers to poll them over a  
>>> serial link
>>> (3 wires). Works well enough even when polling at pretty low speeds.
>>
>> Interesting . All though I don't quiet get it. What is clocking the  
>> Shift
>> register when it's idle? How do you distinguish between the different
>> encoders . Do you have a schematic so I can look at it?
>>
>
> Just go looking in uCApps site again for more midibox schematics,
> You'll find shift register examples from there.. basicly the shift
> register has a defined lenght, so different encoders are just
> different positions in the bits shifted in and all this is done so
> fast that transitions in encoder positions (bits seen by shift
> register) are detected.
>
Aha . Now I get it . It constantly reads the two 8 bits (total 16- 
bit / 8 encoders  in your case 5 encoders 6 buttons awesome :)) status  
and the clocks it over to the µCU. And do I understand it correctly :  
If pin 1  are (IC1/IC5)  Low (SH Pin Low) then the Shift Register IC's  
go into serial input mode and IC5 receives the 8-Bit from IC1?But  
since the IC1's serial input pin 10 is tied ground it will shift out  
the parallel (or 8 Zeros??) data, from IC1, Right?
Does the 10nF to ground help to debounce the pulses from switching?
This is highly interesting thanks for saving me  a lot of input  
pins . :)

Csaba


> Samppa