decoding quadrature encoders

[Luciano]

Hello ICE,

From the PDF file page 3:
http://www.parallax.com/dl/docs/cols...l1/col/nv8.pdf

In the case of the encoder sequence, it turns out that for
any given sequence, XORing the righthand bit of the old value
with the lefthand bit of the new value tells you the direction
of rotation.
For example, take the clockwise sequence 01 00: 1 XOR 0 = 1.
Now the counter-clockwise sequence 01 11: 1 XOR 1 = 0.
This relationship holds for any pair of numbers in either direction.

* * *
The code for the above is:

direction_bit = old.bit0 ^ new.bit1 ' 1 if CW, 0 if CCW

* * *
In your code:

Pause 10 '= 10 milliseconds

* * *
This will help you to debug your code.

Remove the line
LCDOut $fe,1,"no movement"

Replace the lines
LCDOut $fe,1,"one dir" with LCDOut $fe,1,"Last direction was CCW"
LCDOut $fe,1,"2nd dir" with LCDOut $fe,1,"Last direction was CW"


Luciano

[mister_e]

be sure you have pull-up or pull down attach to both output of your encoder.

depending of you rotary encoder model, you can try this thread and monitor the 'value' variable. or modify it easily to have CW and CCW flag in one shot....

[Luciano]

File attachment = Incremental quadrature encoder direction drawing.

Luciano

[ice]

Luciano>>
Thanks for the file..i figured out the logic of the "XOR"..

i included this in my code...[the counting up and counting down lines]

quad:
	new= PORTC & %00000011
	
start:
	old=new & %00000011 

again:
	new= PORTC & %00000011
	IF new=old Then again
	direction_bit=old.bit1 ^ new.bit0
	IF direct=0 Then  cw
	LCDOut $fe,1,"Last was CCW"
	counter=counter+1
	LCDOut $fe,$c0,DEC counter
	Pause 5
	GoTo start
		
cw:
	LCDOut $fe,1,"Last was CW"
	counter=counter-1
	LCDOut $fe,$c0,DEC counter
	Pause 5
	GoTo start

...I am able to see the counter going up and down as the motor changes it's direction..however the LCD line "last was cw/ccw"..keeps on flipping and never remains the same..even if the motor has moved in the same direction..

Im still working on it..and will keep u all posted...

monitor the 'value' variable. or modify it easily to have CW and CCW flag in one shot....

Thanks for the link M_e
..i'll be doing tht to take care of the above problem

[Luciano]

Try this code. (Not tested).

(Problem in your code: you use 'direction_bit' but also 'direct').

Luciano

	old_val VAR BYTE
	new_val VAR BYTE
	direction_bit VAR BIT
	enc_counter VAR WORD

	enc_counter = 10000
	new_val = PORTC & %00000011
start:
	old_val = new_val
again:
	new_val = PORTC & %00000011
	
	IF new_val = old_val Then again

	direction_bit = old_val.bit0 ^ new_val.bit1
	
	IF direction_bit = 1 Then  
	
		LCDOut $fe,1,"Last was CW"
		enc_counter = enc_counter + 1
		LCDOut $fe,$c0,DEC enc_counter

	else
		LCDOut $fe,1,"Last was CCW"
		enc_counter = enc_counter - 1
		LCDOut $fe,$c0,DEC enc_counter	
	
	endif

	GoTo start

[RodSTAR]

File attachment = Incremental quadrature encoder direction drawing.

Luciano

Luciano: five stars!