Smart Pin Quadrature Encoder Demo

JonnyMac

Turns out that using the smart pin quadrature encoder mode is as easy as it seems -- still, it's better to put up real code than to simply talk about it, so here we go.

Interestingly, I tested this across the pin 31-32 boundary and it worked.

Things that I used to do in my P1 encoder cog (preset value, range limiting) turned out easy to handle with simple variables. The object also accounts for those detented encoders that return 4 counts per click (I'm testing with one).

Here's the setup code for the object:

pub start(a, b, btn, d4x, preset, lo, hi) : result | dif

'' Start the encoder object
'' -- continuous count mode
'' -- a & b are encoder inputs (active-low)
'' -- btn is the button input (active-low, -1 if not used)
'' -- set d4x to true if each "click" is 4 counts
'' -- preset is initial value for encoder
'' -- lo & hi are limit values for encoder

  dif := b - a
  if ((dif == 0) or (dif < -3) or (dif > 3))
    result := false
  else
    apin := a                                                   ' save pins & limits
    longmove(@btnpin, @btn, 5)
    mod4x := (d4x) ? 2 : 0                                      ' fix detent modifier
    pinstart(apin, SP_ENC | dif.[2..0] << 24, 0, 0)             ' start a/b quadrature mode
    set(preset)                                                 ' preset encoder value
    result := true

This is the code that returns the encoder value -- handles the 4x detent issue, preset value, and range limiting.

pub value() : result

'' Return encoder value

  result := (rdpin(apin) sar mod4x) + offset
  
  if (result < lolimit)                                         ' limit range
    result := set(lolimit)
  elseif (result > hilimit)
    result := set(hilimit)

Edit: Improved button() method and updated files for PNut v34n.

Publison

Jon, That is an awesome contribution!

Mickster

Thanks Jon.

This such an important feature but has been given no priority which I find to be ridiculous when there is so much emphasis on "ROBOTICS" here.

Instead it's all about graphics which will never compete with the Pi. Go figure.

evanh

Rayman and Roger and Gary and James and Peter and Eric and others have their own interests. They aren't being paid to contribute here. Not everyone is into motion control.
Be happy that there's quadrature hardware in every smartpin. It's just a RDPIN away.