Code Body

To use this file copy and paste this: // #URL-lib "http://pin1.org/forthlib/flb/Examples/rotary2.fth" into BV Terminal 3 or here to download.

// REQUIRES: // #URL-lib "http://pin1.org/forthlib/flb/General/soft1.flb" sid=99 // #URL-lib "http://pin1.org/forthlib/flb/General/pinsel.flb" sid=100

// CONSTANTS: // define the three wires used for the encoder 25 constant line1 26 constant line2 6 constant pushb // integer ra integer rb integer det integer rch

Full Contents of File

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
// Rotary encoders 2
// This version does not use interrupts and culd be easily
// used as a library for other projects.
// This is an alternative to Rotary.fth, it possibly works
// slightly better, uses a pattern to detect direction rather
// then detent
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

// REQUIRES:
// #URL-lib "http://pin1.org/forthlib/flb/General/soft1.flb" sid=99
// #URL-lib "http://pin1.org/forthlib/flb/General/pinsel.flb" sid=100

// 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
//
i n t e g e r r a
i n t e g e r r b
i n t e g e r d e t
i n t e g e r r c h

// A rotary encoder presents two switches that are alternatively
// switched on and off.
// This method works by detecting a pattern that is composed of the
// state of the switched last read to this read. If ra,rb are the current
// state andf
// ra rb
// 0 1 0 0 4
// 1 1 0 1 D
// 1 0 1 1 B
// 0 0 1 0 2
// 0 1 0 0 4 etc.
//
// For the other way
// ra rb
// 1 1 1 0 E
// 0 1 1 1 7
// 0 0 0 1 1
// 1 0 0 0 8
// 1 1 1 0 E etc.
//
// r-pat creates this pattern, by determining which pattern is presented
// the direction of rotation can be obtained.
//

// 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 + R a 1 a n d x o r
;
// ( --- 1|0)
: rb@? // detect change
l i n e 2 p @ 1 + 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
r a @? // delay if required here for switch debounce
i f // still different
l i n e 1 p @ 1 + => R a
t h e n
t h e n
R a
;

: Rb@
r b @? // changed
i f
r b @?
i f // still different
l i n e 2 p @ 1 + => R b
t h e n
t h e n
R b
;

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

// detects a change in any of the a,b switches -1 if there has been a change
// since last read
: ch? ( -- -1|0) r a @ r b @ + r c h <> i f -1 r a @ r b @ + => r c h e l s e 0 t h e n ;

// retunrs set and -1 or 0. Det is one of 4 values consisting of a pattern
// for anti clockise [2,4,&b,&d] and clockwise [1,7,8,&e]
// If there has been no change since last read, then it will return 0
: r-pat ( -- det, -1|0)
c h ?
i f
d e t 2 r s h i f t // move ra,rb to
3 a n d // clear bits 2&3
r a @ 8 * + // ad ra
r b @ 4 * + // add rb
=> d e t // put back
d e t -1
e l s e
0
t h e n
;

// returns x = 1 for clockwise and -1 for anticlockwase followed by -1
// if there have been no chenges it returns 0 on its own
: r-rot ( -- x, -1|0)
r -p a t // get rotary pattern
i f
c a s e
2 o f -1 e n d o f
4 o f -1 e n d o f
&b o f -1 e n d o f
&d o f -1 e n d o f
o t h e r w i s e 1
e n d c a s e
-1
e l s e
0
t h e n
;

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