Probe to read quadrature encoder with DT_INT need help

[Acetronics2]

Just try PortB.7 and PortB.6 ...

and read the '877 Databook , Interrupts section :

WHICH are the 4 pins that create "interrupts on change" ???

HOW to avoid the " Mismatch condition " ???

Alain

[phoenix_1]

These code count pulses from one pin of quadrature encoder good and fast.
It use RB0 INT very good.
Now I need idea to implement full reading quadrature encoder A and B inputs with count of pulses and direction indication..
Encoder is with 500 pulses per full revolution.
How - need idea..?
Procesor 16F877 @ 20MHz

define OSC 20
DEFINE HSER_RCSTA 90h ' Enable serial port & continuous receive
DEFINE HSER_TXSTA 24h ' Enable transmit, BRGH = 1
DEFINE HSER_SPBRG 64  ' 19200 Baud @ 20MHz, 0.16%
DEFINE HSER_CLROERR 1 ' Clear overflow automatically

ADCON1 = 7                       
TRISB = %00000011
a var word
a = 0
INTCON = %10010000 ; Enable INTE RB0 interrupt $90 
INCLUDE "DT_INTS-14.bas" 
INCLUDE "ReEnterPBP.bas" 
ASM
INT_LIST macro ; IntSource, Label, Type, ResetFlag?
    INT_Handler INT_INT,    _TEST,  PBP, yes
    endm
    INT_CREATE ; Creates the interrupt processor
ENDASM

Main: 
if a >= 5000 then
a = 0
endif
hserout [ dec a ]
pause 100
GOTO Main

'---[INT_INT - interrupt handler]------------------------------------------

TEST:
a = a + 1
@   INT_RETURN

Regards Robert

[aratti]

Connect encoder channel A to portB.0 (I assume you already have it) and channel B to portB.1. Since channel A is out of phase on channel B turning your encoder CW channel A will be high before channel B and turning it CCW channel B will be high first.

In your interrupt handler check the above conditions

If portB & %00000011 = 1 Then
a = a + 1
CW = 1
Else
a = a - 1
CW = 0
Endif

If variable CW is 1 then your motor is turning clockwise if CW = 0 then is turning counterclockwise, while word variable a will contain the updated count.

Al.

[aratti]

I have forgotten to say, in my previuos post, that the code snippet is not a quadrature count, and it counts only channel A, while Channel B is used only for direction. So total count per encoder turn will be n/2.

To get a quadrature count you need to detect the rising and falling edges of the square waves, thing that is not possible with the pic you have in use. To obtain the quadrature count you either need additional external logic or you have to choose a pic with the quadrature counter. (Much easier)

Al.

[phoenix_1]

I have forgotten to say, in my previuos post, that the code snippet is not a quadrature count, and it counts only channel A, while Channel B is used only for direction. So total count per encoder turn will be n/2.

To get a quadrature count you need to detect the rising and falling edges of the square waves, thing that is not possible with the pic you have in use. To obtain the quadrature count you either need additional external logic or you have to choose a pic with the quadrature counter. (Much easier)

Al.

Yes I was buy today 18F4431 for start...
But there is 400 pages of datasheet and I need to be a WIZARD to SETUP that PIC

Regards Robert