nicholastyc
Jun 16 2008, 3:33 AM
Hi,
I have problem writing a code for the shaft encoder to decode for my PIC to read the direction.
Can some one please give me a sample code of the shaft encoder decodes the direction?
thanks.
I have problem writing a code for the shaft encoder to decode for my PIC to read the direction.
Can some one please give me a sample code of the shaft encoder decodes the direction?
thanks.
nicholastyc
Jun 16 2008, 3:51 AM
Ajay, i know you already told me about this...but i try to work it out on ASM code...it doesnot work..
can u give me a sample code of how to decode the shaft encoder direction?
can u give me a sample code of how to decode the shaft encoder direction?
nicholastyc
Jun 16 2008, 4:14 AM
GPIO 4 is the channel A of the shaft encoder
GPIO 5 is the channel B of the shaft encoder
below is part of the program code for the encoder to decode the 4 binary bit to determine the direction.
shaft encoder used Bourns ECW- Digital Contacting Encoder
START
btfsc GPIO,4; waiting for the encoder changes
goto START; keep check for the changes
call SHAFT_0; changes detected
SHAFT_0:
CLRF A11 ; clear memory A11
CLRF A21 ; clear memory A21
BCF STATUS,C; clear carry flag incase there is carry
BTFSC GPIO,4 ; check on the changes, 0 or 1
GOTO SAVEBIT_A11 ; if 1 go savebitA11
GOTO SAVEBIT_A10 ;if 0 go savebit A10
SHAFT_1
BTFSC GPIO,5 ; check on gpio 5 changes, channel B
GOTO SAVEBIT_B11 ;if 1 go savebit B11
GOTO SAVEBIT_B10 ;if 0 go savebit B10
SHAFT_2
BTFSC GPIO,4 ;same as above to check to the 4th bit
GOTO SAVEBIT_A21 ;
GOTO SAVEBIT_A20 ;
SHAFT_3
BTFSC GPIO,5 ;
GOTO SAVEBIT_B21 ;
GOTO SAVEBIT_B20 ;
SAVEBIT_A11
MOVLW b'00000001' ; if 1 received on shaft channel A move 1 to A11 memory
MOVWF A11 ;
RLF A11,1 ; rotate left to make bit 0 avaible for channel B
GOTO SHAFT_1 ;
SAVEBIT_A10
MOVLW b'00000000' ;if 0 received on shaft channel A move 1 to A11 memory
MOVWF A11 ;
RLF A11,1 ;rotate left to make bit 0 avaible for channel B
GOTO SHAFT_1 ;
SAVEBIT_B11
MOVLW b'00000001' ; if 1 received on shaft channel B move 1 to A11 memory
IORWF A11,1 ;added up with channel B to form 1 complete bit for
RLF A11,1 ;each turn, rotate left 2 times for next bit of turn
RLF A11,1 ; of the encoder
GOTO SHAFT_2 ;
SAVEBIT_B10
MOVLW b'00000000' ; same as above ...for 0 bit on channel B
IORWF A11,1 ;
RLF A11,1 ;
RLF A11,1
GOTO SHAFT_2 ;
SAVEBIT_A21
MOVLW b'00000001' ;if 1 received on shaft channel A move 1 to A21 memory
MOVWF A21 ;
RLF A21,1 ;rotate left to make bit 0 avaible for channel B
GOTO SHAFT_3 ;
SAVEBIT_A20
MOVLW b'00000000' ;
MOVWF A21 ;same as above
RLF A21,1 ;
GOTO SHAFT_3 ;
SAVEBIT_B21
MOVLW b'00000001' ;bit 1 , added up with channel A to form 1 complete bit for
IORWF A21,0 ;each turn
IORWF A11,0 ;at here, add up 2 complete bit to determine the
GOTO DIRECTION ; direction of the shaft encoder...
SAVEBIT_B20
MOVLW b'00000000' ;same as above, but 0 bit received from previous action
IORWF A21,0 ;
IORWF A11,0 ;
GOTO DIRECTION ;
DIRECTION
CALL TABLE_1 ; call table to check on the direction after the total 4bit added
ANTI_CLOCKWISE
BSF GPIO, 0; set gpio 0 high
BCF GPIO,1; clear gpio 1
goto START;
CLOCKWISE
BSF GPIO,1;set gpio 1 high
BCF GPIO,0;clear gpio 0
GOTO START;
RESTART_PWM
GOTO START; no changes go back to start
RETURN
;************************************************
;**** DIRECTION TABLE****************************
;************************************************
TABLE_1:
ADDWF PCL,1 ;
GOTO RESTART_PWM ;
GOTO ANTI_CLOCKWISE ;
GOTO CLOCKWISE ;
GOTO RESTART_PWM ;
GOTO CLOCKWISE ;
GOTO RESTART_PWM ;
GOTO RESTART_PWM ;
GOTO ANTI_CLOCKWISE ;
GOTO ANTI_CLOCKWISE ;
GOTO RESTART_PWM ;
GOTO RESTART_PWM ;
GOTO CLOCKWISE ;
GOTO RESTART_PWM ;
GOTO CLOCKWISE ;
GOTO ANTI_CLOCKWISE ;
GOTO RESTART_PWM ;
RETURN
GPIO 5 is the channel B of the shaft encoder
below is part of the program code for the encoder to decode the 4 binary bit to determine the direction.
shaft encoder used Bourns ECW- Digital Contacting Encoder
CODE:
START
btfsc GPIO,4; waiting for the encoder changes
goto START; keep check for the changes
call SHAFT_0; changes detected
SHAFT_0:
CLRF A11 ; clear memory A11
CLRF A21 ; clear memory A21
BCF STATUS,C; clear carry flag incase there is carry
BTFSC GPIO,4 ; check on the changes, 0 or 1
GOTO SAVEBIT_A11 ; if 1 go savebitA11
GOTO SAVEBIT_A10 ;if 0 go savebit A10
SHAFT_1
BTFSC GPIO,5 ; check on gpio 5 changes, channel B
GOTO SAVEBIT_B11 ;if 1 go savebit B11
GOTO SAVEBIT_B10 ;if 0 go savebit B10
SHAFT_2
BTFSC GPIO,4 ;same as above to check to the 4th bit
GOTO SAVEBIT_A21 ;
GOTO SAVEBIT_A20 ;
SHAFT_3
BTFSC GPIO,5 ;
GOTO SAVEBIT_B21 ;
GOTO SAVEBIT_B20 ;
SAVEBIT_A11
MOVLW b'00000001' ; if 1 received on shaft channel A move 1 to A11 memory
MOVWF A11 ;
RLF A11,1 ; rotate left to make bit 0 avaible for channel B
GOTO SHAFT_1 ;
SAVEBIT_A10
MOVLW b'00000000' ;if 0 received on shaft channel A move 1 to A11 memory
MOVWF A11 ;
RLF A11,1 ;rotate left to make bit 0 avaible for channel B
GOTO SHAFT_1 ;
SAVEBIT_B11
MOVLW b'00000001' ; if 1 received on shaft channel B move 1 to A11 memory
IORWF A11,1 ;added up with channel B to form 1 complete bit for
RLF A11,1 ;each turn, rotate left 2 times for next bit of turn
RLF A11,1 ; of the encoder
GOTO SHAFT_2 ;
SAVEBIT_B10
MOVLW b'00000000' ; same as above ...for 0 bit on channel B
IORWF A11,1 ;
RLF A11,1 ;
RLF A11,1
GOTO SHAFT_2 ;
SAVEBIT_A21
MOVLW b'00000001' ;if 1 received on shaft channel A move 1 to A21 memory
MOVWF A21 ;
RLF A21,1 ;rotate left to make bit 0 avaible for channel B
GOTO SHAFT_3 ;
SAVEBIT_A20
MOVLW b'00000000' ;
MOVWF A21 ;same as above
RLF A21,1 ;
GOTO SHAFT_3 ;
SAVEBIT_B21
MOVLW b'00000001' ;bit 1 , added up with channel A to form 1 complete bit for
IORWF A21,0 ;each turn
IORWF A11,0 ;at here, add up 2 complete bit to determine the
GOTO DIRECTION ; direction of the shaft encoder...
SAVEBIT_B20
MOVLW b'00000000' ;same as above, but 0 bit received from previous action
IORWF A21,0 ;
IORWF A11,0 ;
GOTO DIRECTION ;
DIRECTION
CALL TABLE_1 ; call table to check on the direction after the total 4bit added
ANTI_CLOCKWISE
BSF GPIO, 0; set gpio 0 high
BCF GPIO,1; clear gpio 1
goto START;
CLOCKWISE
BSF GPIO,1;set gpio 1 high
BCF GPIO,0;clear gpio 0
GOTO START;
RESTART_PWM
GOTO START; no changes go back to start
RETURN
;************************************************
;**** DIRECTION TABLE****************************
;************************************************
TABLE_1:
ADDWF PCL,1 ;
GOTO RESTART_PWM ;
GOTO ANTI_CLOCKWISE ;
GOTO CLOCKWISE ;
GOTO RESTART_PWM ;
GOTO CLOCKWISE ;
GOTO RESTART_PWM ;
GOTO RESTART_PWM ;
GOTO ANTI_CLOCKWISE ;
GOTO ANTI_CLOCKWISE ;
GOTO RESTART_PWM ;
GOTO RESTART_PWM ;
GOTO CLOCKWISE ;
GOTO RESTART_PWM ;
GOTO CLOCKWISE ;
GOTO ANTI_CLOCKWISE ;
GOTO RESTART_PWM ;
RETURN
Ajay
Jun 16 2008, 7:45 AM
Welcome back nich well in your program you have used so many returns.. i really have no idea where you're returning 
Well minute changes will make your program work..
like..
START
btfsc GPIO,4; waiting for the encoder changes
goto START; keep check for the changes
;call SHAFT_0; changes detected
;No need to call the next statement is same you are going to execute
I found that there is no while(1) kind of loop in your program.
please tell me what your application is or what you are trying to do in your program, so that i can optimize it better. and please review your code and remove the unwanted returns, because they will make your program to go mad and hang!!
Well minute changes will make your program work..
like..
CODE:
START
btfsc GPIO,4; waiting for the encoder changes
goto START; keep check for the changes
;call SHAFT_0; changes detected
;No need to call the next statement is same you are going to execute
I found that there is no while(1) kind of loop in your program.
please tell me what your application is or what you are trying to do in your program, so that i can optimize it better. and please review your code and remove the unwanted returns, because they will make your program to go mad and hang!!
nicholastyc
Jun 16 2008, 8:17 AM
hihi, ajay,
my application is for the LED dimmer, i need to know when i am turning clockwise or anti clockwise of the encoder, the light is either dimmer or brighter.
i want to know the changes of direction, so i can set the PWM.
Thanks
Ajay, the main problem i m having now is, how to detect the changes of the encoder signal bits, and how to save them efficiently and bring them to determine the direction using IOR table i am using.
thanks...
my application is for the LED dimmer, i need to know when i am turning clockwise or anti clockwise of the encoder, the light is either dimmer or brighter.
i want to know the changes of direction, so i can set the PWM.
Thanks
Ajay, the main problem i m having now is, how to detect the changes of the encoder signal bits, and how to save them efficiently and bring them to determine the direction using IOR table i am using.
thanks...
shyam
Jun 17 2008, 6:23 AM
hi
nicholastyc
if u had searched the forum u wud have found an earlier post on the similar topic.
still lemme tell u one technique which i use..
u get two o/p lines
say A and B
u get data in gray code format (cyclic).
thhere will be two sets of data
1. clockwise (depends on what pin A or B is)
A|B
0|0
0|1
1|1
1|0
and
2. anticlockwise
A|B
0|0
1|0
1|1
0|1
now u wud have observed the difference just compare any two occurance of data and u will find the direction...
hope that helps...
nicholastyc
if u had searched the forum u wud have found an earlier post on the similar topic.
still lemme tell u one technique which i use..
u get two o/p lines
say A and B
u get data in gray code format (cyclic).
thhere will be two sets of data
1. clockwise (depends on what pin A or B is)
A|B
0|0
0|1
1|1
1|0
and
2. anticlockwise
A|B
0|0
1|0
1|1
0|1
now u wud have observed the difference just compare any two occurance of data and u will find the direction...
hope that helps...
Ajay
Jun 17 2008, 7:41 AM
like you have done in C already, here also you need to make a look up table for encoder to detect the change in direction.
or... what you can do is.. create three states (CLOCK, ANTICLOCK, NOCHANGE)
like this:
if encoder can be connected to interrupt pins of controller or periodic polling on any two pins, then whenever you sense a change in encoder o/p you can switch between states according to current state of encoder bits.
hence in your main loop when a state changes you can do work according to that state.
I hope you have got my idea?
or... what you can do is.. create three states (CLOCK, ANTICLOCK, NOCHANGE)
like this:
CODE:
CLOCK equ 1H
ANTICLOCK equ 2H
NOCHANGE equ 3H
ANTICLOCK equ 2H
NOCHANGE equ 3H
if encoder can be connected to interrupt pins of controller or periodic polling on any two pins, then whenever you sense a change in encoder o/p you can switch between states according to current state of encoder bits.
hence in your main loop when a state changes you can do work according to that state.
I hope you have got my idea?
nicholastyc
Jun 18 2008, 1:11 AM
I was using both of your idea in my design, i make it working on hardware now...but littlt buggy is that...when u over turned the shaft encoder, the light from the dimmest will changed to Brightest ...lol...
little buggy with my code here...need to prevent it to overshoot....
thanks anyway...i will figure it out...
little buggy with my code here...need to prevent it to overshoot....
thanks anyway...i will figure it out...
nicholastyc
Jun 19 2008, 9:02 AM
CODE:
for example:
START
btfss GPIO,4; check encoder changes
goto START
clrf SWDAT2; clear reg
btfss GPIO,4 ; if bit A lo
bsf SWDAT2,0 ; set SWDAT2 bit 0
btfss GPIO,5 ; if bit B lo
bsf SWDAT2,1 ; set SWDAT2 bit 1
movf SWDAT2,W ; load switch data |B0
andlw b'00000011' ; mask encoder B and A switches |B0
xorwf ENCOLD,W ; same as last reading? |B0
bz START ; yes, branch (no change), else |B0
xorwf ENCOLD,W ; restore encoder bits in W |B0
rrf ENCOLD,f ; prep for B-old ^ A-new |B0
xorwf ENCOLD,f ; ENCOLD bit 0 = direction |B0
rrf ENCOLD,f ; now Carry bit = direction |B0
movwf ENCOLD ; update ENCOLD (new BA bits) |B0
btfss STATUS,C;
goto ANTI_CLOCKWISE;
goto CLOCKWISE;
i m using pic12f629...
can some one suggest me a WORKED code?
nicholastyc
Jun 19 2008, 2:59 PM
Shyam , Ajay...Arun...
i really need help on the encoder part...please help..i already tried my best !
i still cant get the right direction ... i m using pic12f629 ...
i am using Gpio,4 and gpio,5 as Bit A and Bit B of encoder.
1. clockwise
A|B
0|0
0|1
1|1
1|0
and
2. anticlockwise
A|B
0|0
1|0
1|1
0|1
how to make a correct table? i m trying to make 1...its works on the simulation but failed on hardware...dunno y...
do i need the interrupt routine? because i m using the btfss gpio,4 to enter the direction loop and then check on the bit on A and B. same as the code in the thread above...
pplease have a look...or give me a code to try...i m so so so depressed!
thanks
i really need help on the encoder part...please help..i already tried my best !
i still cant get the right direction ... i m using pic12f629 ...
i am using Gpio,4 and gpio,5 as Bit A and Bit B of encoder.
1. clockwise
A|B
0|0
0|1
1|1
1|0
and
2. anticlockwise
A|B
0|0
1|0
1|1
0|1
how to make a correct table? i m trying to make 1...its works on the simulation but failed on hardware...dunno y...
do i need the interrupt routine? because i m using the btfss gpio,4 to enter the direction loop and then check on the bit on A and B. same as the code in the thread above...
pplease have a look...or give me a code to try...i m so so so depressed!
thanks
shyam
Jun 19 2008, 10:57 PM
hi nic,
well u do need those A and B pin as interrupt pins.. or else u may miss the step changes..
or u can try one thing....
wait until states are 1,1
wait for either 0,1 or 1,0
accordigly u wud come 2 know the direction of rotation..
one more point to note..
the shaft is usually very sensitive...
if u are rotating by self (ur hand) well u might observe both the direction so dont panic .. stay calm cause u are using the right procedure..
off topic: any new development regarding your job searh?
all the best.
well u do need those A and B pin as interrupt pins.. or else u may miss the step changes..
or u can try one thing....
wait until states are 1,1
wait for either 0,1 or 1,0
accordigly u wud come 2 know the direction of rotation..
one more point to note..
the shaft is usually very sensitive...
if u are rotating by self (ur hand) well u might observe both the direction so dont panic .. stay calm cause u are using the right procedure..
off topic: any new development regarding your job searh?
all the best.
nicholastyc
Jun 20 2008, 12:04 AM
Hi Shyam, wat is mean by
wait until states are 1,1 , 0,1 or 1,0 ?
is it i need to test the both bit in order to enter the loop for testing the direction?
off topic: i havent start to look for job now...i will start this weekend. do u know any job related in UK? thanks...
wait until states are 1,1 , 0,1 or 1,0 ?
is it i need to test the both bit in order to enter the loop for testing the direction?
off topic: i havent start to look for job now...i will start this weekend. do u know any job related in UK? thanks...
shyam
Jun 20 2008, 12:23 AM
is it i need to test the both bit in order to enter the loop for testing the direction?
nic,
take a variable say
int EncCount_int.
int EncStateClk_int[]= {3,2,0,1};
int EncStateAntiClk_int[]= {3,1,0,2};
since the encoder is fast enough .. there is no harm in waiting for that particular stste that u can mark as START.
case1.
if u r not using the pins as interrupt.
start loop.
now u will have to make the uC idle untill the next state change.. i.e. keep checking for the pins untill u notice a change in either of the pin.
read the pins and store in a vriable
int Pinval_int;
int index =1;
now check
if Pinval_int = EncStateClk_int[index]
// clock wise rotation
//decrease EncCount_int
EncCount_int = EncCount_int -1;
else
// anticlock wise rotation
//increase EncCount_int
EncCount_int= EncCount_int+1;
//increment index;
if ( index ==4)
index =0;
get back to the loop
sorry for not being clear enough... am amidst a project needing some attention...
please se if it helps...
nicholastyc
Jun 20 2008, 4:32 AM
i think something is wrong with my code that its only detects 1 direction!!
i have made my program on interrupt on change to the both input port,
the will go into the ISR to save the bit data...
but its still failed to detect the correct direction.
why?
thanks Shyam for your times...i still failed..
i have made my program on interrupt on change to the both input port,
the will go into the ISR to save the bit data...
but its still failed to detect the correct direction.
why?
thanks Shyam for your times...i still failed..
Ajay
Jun 20 2008, 8:26 AM
can i see your code again?
shyam
Jun 20 2008, 8:36 AM
yes lets see the code again.. the interrupt one.
sashijoseph
Jun 20 2008, 11:26 PM
Hi Nic,
This is a small adaptation of your polling routine using a single variable A11.It savs the current and previous AB values in this manner as a nibble....
This is a small adaptation of your polling routine using a single variable A11.It savs the current and previous AB values in this manner as a nibble....
CODE:
START
CLRF A11 ; clear memory A11
BCF STATUS,C; clear carry flag incase there is carry
SHAFT_0
BTFSC GPIO,4 ; check on the changes, 0 or 1
GOTO SAVEBIT_A11 ; if 1 go savebitA11
GOTO SAVEBIT_A10 ;if 0 go savebit A10
SHAFT_1
BTFSC GPIO,5 ; check on gpio 5 changes, channel B
GOTO SAVEBIT_B11 ;if 1 go savebit B11
GOTO SAVEBIT_B10 ;if 0 go savebit B10
SHAFT_2
BTFSC GPIO,4 ;same as above to check to the 4th bit
GOTO SAVEBIT_A21 ;
GOTO SAVEBIT_A20 ;
SHAFT_3
BTFSC GPIO,5 ;
GOTO SAVEBIT_B21 ;
GOTO SAVEBIT_B20 ;
SAVEBIT_A11
MOVLW b'00000001' ; if 1 received on shaft channel A move 1 to A11 memory
MOVWF A11 ;
RLF A11,1 ; rotate left to make bit 0 avaible for channel B
GOTO SHAFT_1 ;
SAVEBIT_A10
MOVLW b'00000000' ;if 0 received on shaft channel A move 1 to A11 memory
MOVWF A11 ;
RLF A11,1 ;rotate left to make bit 0 avaible for channel B
GOTO SHAFT_1 ;
SAVEBIT_B11
MOVLW b'00000001' ; if 1 received on shaft channel B move 1 to A11 memory
IORWF A11,1 ;added up with channel B to form 1 complete bit for
RLF A11,1 ;each turn, rotate left 2 times for next bit of turn
of the encoder
GOTO SHAFT_2 ;
SAVEBIT_B10
MOVLW b'00000000' ; same as above ...for 0 bit on channel B
IORWF A11,1 ;
RLF A11,1 ;
GOTO SHAFT_2 ;
SAVEBIT_A21
MOVLW b'00000001' ;if 1 received on shaft channel A move 1 to A21 memory
IORWF A11,1 ;
RLF A11,1 ;rotate left to make bit 0 avaible for channel B
GOTO SHAFT_3 ;
SAVEBIT_A20
MOVLW b'00000000' ;
IORWF A11,1 ;same as above
RLF A11,1 ;
GOTO SHAFT_3 ;
SAVEBIT_B21
MOVLW b'00000001' ;bit 1 , added up with channel A to form 1 complete bit for
IORWF A11,1
GOTO DIRECTION ; direction of the shaft encoder...
SAVEBIT_B20
MOVLW b'00000000' ;same as above, but 0 bit received from previous action
IORWF A11,1 ;
GOTO DIRECTION ;
RET_FROM_DIRECTION
RLF A11,1
MOVLW b'00000110'
ANDWF A11,1
GOTO SHAFT_2
DIRECTION
......
......
GOTO RET_FROM_DIRECTION
CLRF A11 ; clear memory A11
BCF STATUS,C; clear carry flag incase there is carry
SHAFT_0
BTFSC GPIO,4 ; check on the changes, 0 or 1
GOTO SAVEBIT_A11 ; if 1 go savebitA11
GOTO SAVEBIT_A10 ;if 0 go savebit A10
SHAFT_1
BTFSC GPIO,5 ; check on gpio 5 changes, channel B
GOTO SAVEBIT_B11 ;if 1 go savebit B11
GOTO SAVEBIT_B10 ;if 0 go savebit B10
SHAFT_2
BTFSC GPIO,4 ;same as above to check to the 4th bit
GOTO SAVEBIT_A21 ;
GOTO SAVEBIT_A20 ;
SHAFT_3
BTFSC GPIO,5 ;
GOTO SAVEBIT_B21 ;
GOTO SAVEBIT_B20 ;
SAVEBIT_A11
MOVLW b'00000001' ; if 1 received on shaft channel A move 1 to A11 memory
MOVWF A11 ;
RLF A11,1 ; rotate left to make bit 0 avaible for channel B
GOTO SHAFT_1 ;
SAVEBIT_A10
MOVLW b'00000000' ;if 0 received on shaft channel A move 1 to A11 memory
MOVWF A11 ;
RLF A11,1 ;rotate left to make bit 0 avaible for channel B
GOTO SHAFT_1 ;
SAVEBIT_B11
MOVLW b'00000001' ; if 1 received on shaft channel B move 1 to A11 memory
IORWF A11,1 ;added up with channel B to form 1 complete bit for
RLF A11,1 ;each turn, rotate left 2 times for next bit of turn
of the encoder
GOTO SHAFT_2 ;
SAVEBIT_B10
MOVLW b'00000000' ; same as above ...for 0 bit on channel B
IORWF A11,1 ;
RLF A11,1 ;
GOTO SHAFT_2 ;
SAVEBIT_A21
MOVLW b'00000001' ;if 1 received on shaft channel A move 1 to A21 memory
IORWF A11,1 ;
RLF A11,1 ;rotate left to make bit 0 avaible for channel B
GOTO SHAFT_3 ;
SAVEBIT_A20
MOVLW b'00000000' ;
IORWF A11,1 ;same as above
RLF A11,1 ;
GOTO SHAFT_3 ;
SAVEBIT_B21
MOVLW b'00000001' ;bit 1 , added up with channel A to form 1 complete bit for
IORWF A11,1
GOTO DIRECTION ; direction of the shaft encoder...
SAVEBIT_B20
MOVLW b'00000000' ;same as above, but 0 bit received from previous action
IORWF A11,1 ;
GOTO DIRECTION ;
RET_FROM_DIRECTION
RLF A11,1
MOVLW b'00000110'
ANDWF A11,1
GOTO SHAFT_2
DIRECTION
......
......
GOTO RET_FROM_DIRECTION
sashijoseph
Jun 20 2008, 11:40 PM
Now for the nibble A11 you can have the following valid values
0x01,0x07,0x08 and 0x0E representing clockwise direction
and
0x2,0x04,0x0B,0x0D representing anticlock direction.
Thus you need to check the nibble for 1,7,8 or E (hex) for a clockwise rot and 2,4,B or D for anti.
Any other value means either no change or invalid... so you need to ignore.
In the 'direction' part of the code you need to implement this logic.
After that the nibble is rotated left once and 'anded' with 00000110 to save the current AB value(which will now become the previous AB value) and the loop is started again for acquiring the current AB value.
0x01,0x07,0x08 and 0x0E representing clockwise direction
and
0x2,0x04,0x0B,0x0D representing anticlock direction.
Thus you need to check the nibble for 1,7,8 or E (hex) for a clockwise rot and 2,4,B or D for anti.
Any other value means either no change or invalid... so you need to ignore.
In the 'direction' part of the code you need to implement this logic.
After that the nibble is rotated left once and 'anded' with 00000110 to save the current AB value(which will now become the previous AB value) and the loop is started again for acquiring the current AB value.
Arun Kumar V
Jun 21 2008, 4:55 AM
Hi nic,
i think SJ nailed it !
Arun