Code Body

To use this file copy and paste this: // #URL-lib "http://pin1.org/forthlib/flb/Examples/rotary.fth" into BV Terminal 3 or here to download.

// REQUIRES: // #URL-lib "http://pin1.org/forthlib/flb/General/pinsel.flb"

// CONSTANTS: // define the three wires used for the encoder 25 constant line1 26 constant line2 6 constant pushb // variable oldRa variable oldRb variable detent variable temp

Full Contents of File

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
// Rotary encoders 1
// This version does not use interrupts and culd be easily
// used as a library for other projects.
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

// REQUIRES:
// #URL-lib "http://pin1.org/forthlib/flb/General/pinsel.flb"

// CONSTANTS:
// define the three wires used for the encoder
2 5 c o n s t a n t l i n e 1
2 6 c o n s t a n t l i n e 2
6 c o n s t a n t p u s h b
//
v a r i a b l e o l d R a
v a r i a b l e o l d R b
v a r i a b l e d e t e n t
v a r i a b l e t e m p

// A rotary encoder presents two switches that are alternatively
// switched on and off. There is a DETENT period when the switches
// are either both on or both off, i.e the same. What happens after
// this determines the direction of rotation. If follows from this
// description that this is dynamic, the state of the switches must
// be read only AFTER the detent state.
//
// Looking at two outputs A and B
// time1 Aon + Bon = detent+
// time2 Aoff + Bon = clockwise
//
// time1 Aoff + Boff = detent-
// time2 Aon + Boff = clockwise
//
// The reading is therfore a two stage process, the detent stage and
// the read stage, only one channel needs to be read as follows:
// After detent:
// detent+ and Aoff = clocwise, detenet+ and Aon = CCW
// detent- and Aon = clockwise, detent- and Aoff = CCW
//
// We have therfore 3 states of detent 0, + and -, + and - where
// both A and B are on and 0 where either A to B is off.
//

// Set up rotary encoder lines A and B
: r-set
l i n e 1 i o -i n
l i n e 2 i o -i n
p u s h b i o -i n // push switch
;

// return 1 if the values are different
// from last time
// ( --- 1|0)
: ra@? // detect change
l i n e 1 p @ 1 + o l d R a @ 1 a n d x o r
;
// ( --- 1|0)
: rb@? // detect change
l i n e 2 p @ 1 + o l d R b @ 1 a n d x o r
;
// this is a pin detect with switch debounce
// returns 1 when off 0 when on
// ( --- 1/0)
: Ra@
r a @? // changed
i f
1 m s r a @?
i f // still different
l i n e 1 p @ 1 + o l d R a !
t h e n
t h e n
o l d R a @ 1 -
;

: Rb@
r b @? // changed
i f
1 m s r b @?
i f // still different
l i n e 2 p @ 1 + o l d R b !
t h e n
t h e n
o l d R b @ 1 -
;

// push switch
// ( value ---)
: Rc@p u s h b p @ ;

// At the switch detent both A and B are either high or
// low, this is noted and saved in DETENT as a value of either
// -1 or 1. *This can only be done when DETANT is = to 0
// When the switch is not at detent, *if detent does not = 0 a
// -1 or +1 is left depending on the combined value of Ra and DETENT
// When the value is left *DETENT is cleared.
// * The variable DETENT is used for saving the previous state of the coincedent
// switches and also as a flag to prevent re-triggering.
// ( --- value, -1 |0)
: r-rot
r a @ r b @ 2 d u p x o r // NOT detent
i f // NOT detent
d r o p // drop Rb
d e t e n t @ // get saved
?d u p
i f // should be > 0 if valid
0 d e t e n t ! // clear detent
x o r // detent+Ra
0 < i f 1 e l s e -1 t h e n // leave value
-1 // and indicator
e l s e
d r o p 0 // drop Rb and leave 0
t h e n
e l s e
d e t e n t @ 0 = // should be 0
i f
+ 1 + // add Ra+Rb+1 gives -1 or 1
d e t e n t ! // save for NOT detent
0 // leave 0
e l s e
2 d r o p 0 // drop Ra+Rb and leave 0
t h e n
t h e n
;

: r-test
r -s e t
0 t e m p !
b e g i n
r -r o t
i f t e m p +! t e m p @ . t h e n
k e y ?
u n t i l
;