Pic question
Archiver
Posts: 46,084
Hi everyone!
I rarely ask for help. I just suffer with frustration but now I must
ask. Please HELP!!
I am using Chuck's Motor controller with speed and direction control.
It uses a PIC16C54. It takes the signal from a remote control
receiver (in my case AIRTRONICS) that ususally goes to the servo, and
depending on where the joystick on the transmitter is, sends a signal
to an ISO circuit which in turn controls a MOSFET bridge which
controls the motor.
The PICS detects the position of the joystick via the signal usually
meant for the servo. The interpretation is then fed out of PORTA. I
have the chips programmed and the receiver connected as required but
I suspect that the signal may not be detected or misread. I don't
have a scope to measure the input from the receiver to the PIC and I
can't determine if the chip is correctly running the program. The
shortcut to this project is here:
http://professionals.com/~cmcmanis/robotics/servo.html
I have studied this and have successfully build the bridge circuit.
It works. I just need to figure out how to test the PIC circuit.
There is a pulse comming from the signal line from the transmitter.(I
have a digital probe).
I know this is not a basic stamp question but I also know that the
PIC and STAMP are virtually the same.
The PIC ASM file is THIS:
TITLE "Electronic Speed Control SERVO SOFTWARE"
LIST P=16C54A, R=HEX, C=120
include "p16C5X.inc"
include "p16c5xd.inc"
__FUSES _CP_OFF&_HS_OSC&_WDT_OFF
;
; ESC Servo Control Software
; Written 12/29/94 by Chuck McManis
;
; Copyright (c) 1994-1995, Chuck McManis all rights reserved.
;
; Modification history:
; * 12/19/94 - Initial release
; * 1/12/95 - Modified to use PORT A for output.
; * 1/18/95 - Timing constants assume a 20Mhz clock.
;
; Data space
;
CBLOCK H'0008'
COUNT_HI ; High Byte of the Count
COUNT_LO ; Low Byte of the Count
TEMP ; Temporary variable
PWM_CMD ; PWM Constant
PWM_TMP ; Temporary counter for PWM count down
CMD_REG ; Motor control command
CMD_TMP ; Temporary copy of CMD_REGS
OUTER_CNT ; Outer loop count
INNER_CNT ; Inner Loop count
GLITCH ; Our glitch count
ENDC
;
; Bridge Control definitions. The output bits are connected as
follows:
; Bit 3 - Left High Side Switch
; Bit 2 - Right High Side Switch
; Bit 1 - Left Low Side Switch
; Bit 0 - Right Low Side Switch
FORWARD_CMD EQU H'89' ; Move forward (Left high + Right
lower)
REVERSE_CMD EQU H'46' ; Move Backward (Right High + Left
Lower)
COAST_CMD EQU H'00' ; Coast (all off)
BRAKE_CMD EQU H'33' ; Brakes on (Left Lower + Right
Lower).
GLITCH_COUNT EQU D'172' ; 860uS (172 * 5 uS, 20 Mhz clock)
DEADBAND EQU D'6' ; Deadband range + 1
; The input pin
#define SERVO_IN PORTB,0
; The H-bridge ouput
#define BRIDGE_OUT PORTA
;
; System initialization code
;
ORG H'1FF' ; Reset Vector (PIC16C54)
GOTO INIT
ORG 0
INIT
MOVLW 0 ; All bits as outputs.
TRIS BRIDGE_OUT ; Output port is all outputs.
CLRF BRIDGE_OUT ; And all outputs OFF.
MOVLW GLITCH_COUNT ; Initialize vars
MOVWF GLITCH ;
MOVWF COUNT_LO ; Initialize count to 0x1A0
MOVLW 1 ;
MOVWF COUNT_HI ;
;
; IDLE combines both the Idle and the Measure states. This is
accomplished
; by the routine DO_MEASURE which can be called when measuring and
when idle.
;
IDLE:
CALL DO_MEASURE ; Measure input pulse
16
MOVWF TEMP ; Store result in TMP
1
MOVF TEMP,F ; Waste time, set Z bit
1
BTFSS ZERO_BIT ; If zero no new value.
2 1
GOTO PWM ; If got a value, then start.
- 2
GOTO $+1 ; Waste time
2
NOP ; ...
1
GOTO IDLE ; Go back to measuring
2
; Total Clocks in
Loop 25
;
; PWM is the loop that generates the PWM output. We do this
; by turning on the H-Bridge and counting down PWM_CMD steps and
; then turning off the bridge. The loop count is effectively 100.
; This gives a direct percentage relationship between the value
; in PWM_CMD and the output. The value 1 is a 1% duty cycle square
; wave and the value 99 is a 99% duty cycle. (100 is 100%) So
; The range of legal inputs is 1 thru 100.
;
; The loop is structured to take 500 uS, the inner loop takes
; 5uS and the outer loop is designed to take 5uS as well.
; Thus 99 inner loop iterations and one outer loop pass == 100 * 5us
; which is 500uS. That yields a PWM frequency of 2000 Hz.
; The outer loop has 40 iterations so that after 20mS, if no
additional
; pulse has been received the loop exits and the H-bridge turns off.
;
; When we exit due to a timeout we must make sure that we keep calling
; DO_MEASURE on schedule because we may be in the middle of measuring
a
; new input pulse. So we dovetail the outer loops return to idle with
; IDLE making the transistion from the PWM+Measuring state to the
; Idle+Measuring state seamless.
;
PWM:
MOVLW D'40' ; Constant for 20 mS
MOVWF OUTER_CNT ; Outer Count
MOVF PWM_CMD,W ; Set up the inner loop counters
MOVWF PWM_TMP
MOVF CMD_REG,W ; Get H-Bridge Command
MOVWF CMD_TMP ; Put it in our temporary holder
MOVWF BRIDGE_OUT ; Turn on the motors
1
MOVLW D'99' ;
1
MOVWF INNER_CNT ;
1
GOTO PWM_LOOP ; Line up command
2 (4)
PWM_LOOP:
CALL DO_MEASURE ; Do a "measurement"
16
;
; If DO_MEASURE found a pulse, it will modify the control variables ;
; PWM_TMP - Set to FF to prevent swaping CMD_REG
; INNER_CNT - Set to 1 so that this loop will exit immediately
; OUTER_CND - Set to 41 so that the outer loop will run for 20mS
; PWM_CMD - Set to the new PWM constant
; CMD_REG - Set to the new H-Bridge Command
;
DECF PWM_TMP,F ; Decrement the "On" time
1\
BTFSC ZERO_BIT ; If not zero continue
2 1
SWAPF CMD_TMP,F ; Turn off the low side
- 1
MOVF CMD_TMP,W ; Get the Command Register
1/
MOVWF BRIDGE_OUT ; Send it To the H-Bridge.
1
MOVF PWM_CMD,W ; Sort of a NOP
1
DECFSZ INNER_CNT,F ; Decrement inner loop count
1 2
GOTO PWM_LOOP ; Continue Looping
2 -
; Total Clocks (inner loop) 25 (5
uS)
;
;
; Outer loop count down, Note we've combined the MOVF PWM_CMD,W
statement
; above with the MOVWF PWM_TMP statement below to accomplish
reinitializing
; PWM_TMP in only 1 cycle. This works because the DECFSZ above doesn't
; change W. Without this trick there is no way for the outer loop to
work
; in the required 5uS and we lose the ability to call do_measure on
schedule.
;
MOVWF PWM_TMP ; Restore PWM command (loaded above)
1
CALL DO_MEASURE ; This is on a 5uS boundary.
16
MOVLW D'99' ; Reset inner loop count
1
MOVWF INNER_CNT ; Like so
1
MOVF CMD_REG,W ; Put command into W
1
MOVWF CMD_TMP ; Re-initialized CMD_TMP
1
MOVWF BRIDGE_OUT ; Send it to the motors
1
DECF OUTER_CNT ;
1
BTFSS ZERO_BIT ;
1 2
GOTO PWM_LOOP ;
2 -
;
; Getting here means we've timed out our 20 mS of looping. However we
; may be in the process of receiving a pulse so we make sure we call
; DO_MEASURE on schedule and essentially duplicate what the IDLE loop
; does and when we're done we loop to IDLE.
;
CLRF BRIDGE_OUT ; Turn off the motors
1
CALL DO_MEASURE ;
16
MOVWF TEMP ; Store result in TMP
1
MOVF TEMP,F ; Waste time, set Z bit
1
BTFSS ZERO_BIT ; If zero no new value.
2 1
GOTO PWM_LOOP ; If got a new value, then start.
- 2
GOTO $+1 ; else Waste time
2
NOP ; ...
1
GOTO IDLE ; Go back to measuring
2
;
; DO_MEASURE is the pulse measuring routine. It is called from either
; Idle or PWM. It implements a mini-state machine the monitors the
; input pin. The code is written so that it is called every 5uS.
; When called, the input will either be high or low. Depending on the
; input pins state, it either measures or doesn't.
; If the input pin is high, we start counting down our counter.
; Each count represents 5uS. If we ever underflow our counter we
; note that as a timeout (the input pulse was too wide.)
;
; If the input pin is low, we process a potential pulse. If
glitch
; is non-zero (input pulse < 860uS) we treat it as a glitch,
reset
; the counters and return. (Note this happens every time when
the
; input pin is low.)
;
; If Glitch is zero we check for a counter underflow (timeout).
If
; the counter has timed out we reset the counters and return.
(Note
; this happens every time when the input pin stays high)
;
; If we pass both of these tests (not a glitch, not a timeout)
we
; process it as a valid pulse, set all of the variables
appropriately
; and return.
;
; Given the Design, this routine _MUST_ always execute in 14 clocks.
The
; The clock counts in the right margin represent the time spent in
; various "paths" through this code.
;
DO_MEASURE:
BTFSC SERVO_IN ; Check for 'high' 2 1
GOTO INP_HIGH ; Yup, count it. - 2
(3)
MOVF GLITCH,F ; Check Glitch counter 1 -
BTFSS ZERO_BIT ; != 0 means Glitch. 2 - 1
GOTO NO_PULSE ; This was a glitch - - 2
(6)
BTFSS COUNT_HI,7 ; Check for overflow 2 - -
1
GOTO GOT_PULSE ; Process a good count - - -
2 (8)
MOVLW GLITCH_COUNT ; Glitch length 1 - -
*
MOVWF GLITCH ; Store it in GLITCH 1 - -
MOVWF COUNT_LO ; Just a glitch, 1 - -
MOVLW 1 ; Load count with constant 1 - -
MOVWF COUNT_HI ; 1 - -
RETLW 0 ; And return 2 - -
; --
; Total 14
;
;
; This is basically an abort, it resets the counters and state
variables
; and returns.
;
NO_PULSE: ; (6)
MOVLW GLITCH_COUNT ; - - 1
MOVWF GLITCH ; - - 1
MOVWF COUNT_LO ; Just a glitch, - - 1
MOVLW 1 ; Load count with 0x1A0 - - 1
MOVWF COUNT_HI ; - - 1
NOP ; To get an even 14 clocks - - 1
RETLW 0 ; And return - - 2
; --
; Total 14
;
;
; Process a "true" input.
;
INP_HIGH: ; (3)
MOVF GLITCH,F ; Check Glitch - 1
BTFSS ZERO_BIT ; Is it already 0? - 2 1
DECF GLITCH ; No, then decrement it - - 1
BTFSC COUNT_HI,7 ; Not a timeout already - 2
1
GOTO INP_TIMEOUT ; Its a timeout - -
2 (9)
MOVF COUNT_LO,F ; Test COUNT_LO for zero - 1
BTFSC ZERO_BIT ; If its zero, this is it - 2 1
DECF COUNT_HI,F ; Subtract one from COUNT_HI - - 1
DECF COUNT_LO,F ; Subtract one from the count -
1 -
RETLW 0 ; - 2
; --
; Total 14
;
;
; During a timeout condition we basically hold the state variables
; where they are so that when the pin goes low it will be detected and
; the variables reset.
;
INP_TIMEOUT: ;
(9)
NOP ; Filler to get 14 clocks - - -
1
NOP ; Filler to get 14 clocks - - -
1
NOP ; Filler to get 14 clocks - - -
1
RETLW 0 ; - - -
2
; -
-
; Total
14
;
;
; Given a valid measurement, calculate a Command and a PWM Constant.
;
; Algorithim:
; Compute Delta = Count - midpoint;
; If (Delta < 0)
; Command = Forward;
; else
; Command = Reverse;
; Delta = ABS(Delta);
; if (Delta <= DEADBAND)
; if (Delta == DEADBAND)
; Command = Coast
; else
; Command = Brake;
; PWM Constant = 100%.
; Else
; PWM Constant = Min(MAX, delta - 8) * 100/MAX.
; (for MAX == 100, this is simply (Min(MAX, delta - 8))
; Return.
;
;
GOT_PULSE: ; (8)
MOVLW D'128' ; This is the midpoint. 1
SUBWF COUNT_LO,F ; 1
BTFSS CARRY_BIT ; Carry is set (no Borrow) 2 1
GOTO DEAL_WITH_MINUS ; Figure out what to do now. - 2
(13)
POSITIVE_RESULT: ;
(+7)
MOVLW REVERSE_CMD ; Its probably reverse 1
MOVWF CMD_REG ; Store it in command register 1
NEW_PWM_VALUE: ;
(21)
MOVLW DEADBAND ; Dead band is +/- 6 (50uS) 1
SUBWF COUNT_LO,F ; Subtract DEADBAND from count. 1
BTFSS CARRY_BIT ; If no borrow, continue 2 1
GOTO DO_BRAKE ; In the dead zone do braking. - 2
(19) (26)
MOVLW D'100' ; Check if its in the range 1
SUBWF COUNT_LO,W ; Subtract 99 (max range) 1
BTFSC CARRY_BIT ; Check if its Less than MAX 2 1
GOTO MAX_PWM ; Was >= 100 - 2
(23) (30)
MOVF COUNT_LO,W ; Get count value. 1
DONE_PULSE: ; (26)
(+12)(33)
MOVWF PWM_CMD ; This is the new PWM Constant 1 1
INCF PWM_CMD ; Adjust 0 - 99 -> 1 to 100% 1 1
MOVLW 1 ; Put 1 into INNER_CNT 1 1
MOVWF INNER_CNT ; 1 1
MOVWF PWM_TMP ; 1 1
MOVWF COUNT_HI ; Reset counter 1 1
MOVLW GLITCH_COUNT ; for next time 1 1
MOVWF COUNT_LO ; 1 1
MOVWF GLITCH ; 1 1
MOVLW D'41' ; Loop count + 1 1 1
MOVWF OUTER_CNT ; 1 1
RETLW 1 ; Return true 2 2
; Totals 36 39
; Totals (max) 46
; Totals (reverse) 43 46
; Totals (do_brake) 44 51
;
; Various exit times depending on the path. Since the spec says that
; another pulse won't start for at least 5mS the results are not
; critical but they are useful to know. They become the true spec for
; the minimum separation between pulses.
;
; Max time 51 * .2 = 10.20uS, Min time 36 * .2 = 7.2uS
;
MAX_PWM:
MOVLW D'100' ; Else max (does MIN(100, val)) 1
GOTO DONE_PULSE ; Fix up loop values 2
;
; If the result was minus, it could be legitimately minus, or it could
; be that count was 0x100. We fix those by checking COUNT_HI.
;
DEAL_WITH_MINUS:
BTFSC COUNT_HI,0 ; Is bit 0 a one? 2 1
GOTO ADJUST_RESULT ; Yes, so adjust - 2
MOVLW FORWARD_CMD ; Its wider than the midpoint 1
MOVWF CMD_REG ; So this is the command. 1
COMF COUNT_LO,F ; Convert to a positive value 1
INCF COUNT_LO,F ; negate COUNT_LO 1
GOTO NEW_PWM_VALUE ; Now go compute PWM constant. 2
ADJUST_RESULT:
MOVLW D'128' ; 256 - 128 = 128 1
MOVWF COUNT_LO ; Fixup the low byte 1
GOTO POSITIVE_RESULT ; Now treat it normally. 2
;
; Now if the value is -DEADBAND thru +DEADBAND we set the command to
; "BRAKE", if it was exactly -DEADBAND or +DEADBAND we set it to
COAST.
; The reason for this is that given our sample rate/accuracy we find
that
; we get 'jitter' in the input that results in a COUNT value that can
move
; between two values on alternate samples. Given that variation, for
input
; pulse widths that are 'near' DEADBAND-1 or -(DEADBAND-1) we could
see
; alternating DEADBAND and DEADBAND-1 on the input. Without a one
value
; buffer, this causes the output to alternate between a little on (1%
PWM)
; and BRAKE. The motor then sits there and stutters. However by
defining
; the value DEADBAND exactly to be '0' the output is either COAST/ON
or
; COAST/BRAKE, both of which have a predictable and non-harmful
output.
;
DO_BRAKE:
MOVLW DEADBAND ; Restore Count Value
1
ADDWF COUNT_LO,F ; Add it back to Count
1
MOVLW DEADBAND-1 ; Check for boundary condition
1
SUBWF COUNT_LO,W ; Subtrack COUNT LO
1
BTFSC ZERO_BIT ; Check to see if its zero
2 1
GOTO ON_THE_EDGE ; Its exactly DEADBAND - 1
- 2
MOVLW BRAKE_CMD ; This is the brake Command
1 -
ON_THE_EDGE:
MOVWF CMD_REG ; Store it
1
MOVLW D'100' ; Very large PWM Constant
1
MOVWF PWM_CMD ; So we get 100% braking action
1
GOTO DONE_PULSE ; Return indicating new value
available.2 (12)
END
Thanks
Gary
gcompanion@h...
I rarely ask for help. I just suffer with frustration but now I must
ask. Please HELP!!
I am using Chuck's Motor controller with speed and direction control.
It uses a PIC16C54. It takes the signal from a remote control
receiver (in my case AIRTRONICS) that ususally goes to the servo, and
depending on where the joystick on the transmitter is, sends a signal
to an ISO circuit which in turn controls a MOSFET bridge which
controls the motor.
The PICS detects the position of the joystick via the signal usually
meant for the servo. The interpretation is then fed out of PORTA. I
have the chips programmed and the receiver connected as required but
I suspect that the signal may not be detected or misread. I don't
have a scope to measure the input from the receiver to the PIC and I
can't determine if the chip is correctly running the program. The
shortcut to this project is here:
http://professionals.com/~cmcmanis/robotics/servo.html
I have studied this and have successfully build the bridge circuit.
It works. I just need to figure out how to test the PIC circuit.
There is a pulse comming from the signal line from the transmitter.(I
have a digital probe).
I know this is not a basic stamp question but I also know that the
PIC and STAMP are virtually the same.
The PIC ASM file is THIS:
TITLE "Electronic Speed Control SERVO SOFTWARE"
LIST P=16C54A, R=HEX, C=120
include "p16C5X.inc"
include "p16c5xd.inc"
__FUSES _CP_OFF&_HS_OSC&_WDT_OFF
;
; ESC Servo Control Software
; Written 12/29/94 by Chuck McManis
;
; Copyright (c) 1994-1995, Chuck McManis all rights reserved.
;
; Modification history:
; * 12/19/94 - Initial release
; * 1/12/95 - Modified to use PORT A for output.
; * 1/18/95 - Timing constants assume a 20Mhz clock.
;
; Data space
;
CBLOCK H'0008'
COUNT_HI ; High Byte of the Count
COUNT_LO ; Low Byte of the Count
TEMP ; Temporary variable
PWM_CMD ; PWM Constant
PWM_TMP ; Temporary counter for PWM count down
CMD_REG ; Motor control command
CMD_TMP ; Temporary copy of CMD_REGS
OUTER_CNT ; Outer loop count
INNER_CNT ; Inner Loop count
GLITCH ; Our glitch count
ENDC
;
; Bridge Control definitions. The output bits are connected as
follows:
; Bit 3 - Left High Side Switch
; Bit 2 - Right High Side Switch
; Bit 1 - Left Low Side Switch
; Bit 0 - Right Low Side Switch
FORWARD_CMD EQU H'89' ; Move forward (Left high + Right
lower)
REVERSE_CMD EQU H'46' ; Move Backward (Right High + Left
Lower)
COAST_CMD EQU H'00' ; Coast (all off)
BRAKE_CMD EQU H'33' ; Brakes on (Left Lower + Right
Lower).
GLITCH_COUNT EQU D'172' ; 860uS (172 * 5 uS, 20 Mhz clock)
DEADBAND EQU D'6' ; Deadband range + 1
; The input pin
#define SERVO_IN PORTB,0
; The H-bridge ouput
#define BRIDGE_OUT PORTA
;
; System initialization code
;
ORG H'1FF' ; Reset Vector (PIC16C54)
GOTO INIT
ORG 0
INIT
MOVLW 0 ; All bits as outputs.
TRIS BRIDGE_OUT ; Output port is all outputs.
CLRF BRIDGE_OUT ; And all outputs OFF.
MOVLW GLITCH_COUNT ; Initialize vars
MOVWF GLITCH ;
MOVWF COUNT_LO ; Initialize count to 0x1A0
MOVLW 1 ;
MOVWF COUNT_HI ;
;
; IDLE combines both the Idle and the Measure states. This is
accomplished
; by the routine DO_MEASURE which can be called when measuring and
when idle.
;
IDLE:
CALL DO_MEASURE ; Measure input pulse
16
MOVWF TEMP ; Store result in TMP
1
MOVF TEMP,F ; Waste time, set Z bit
1
BTFSS ZERO_BIT ; If zero no new value.
2 1
GOTO PWM ; If got a value, then start.
- 2
GOTO $+1 ; Waste time
2
NOP ; ...
1
GOTO IDLE ; Go back to measuring
2
; Total Clocks in
Loop 25
;
; PWM is the loop that generates the PWM output. We do this
; by turning on the H-Bridge and counting down PWM_CMD steps and
; then turning off the bridge. The loop count is effectively 100.
; This gives a direct percentage relationship between the value
; in PWM_CMD and the output. The value 1 is a 1% duty cycle square
; wave and the value 99 is a 99% duty cycle. (100 is 100%) So
; The range of legal inputs is 1 thru 100.
;
; The loop is structured to take 500 uS, the inner loop takes
; 5uS and the outer loop is designed to take 5uS as well.
; Thus 99 inner loop iterations and one outer loop pass == 100 * 5us
; which is 500uS. That yields a PWM frequency of 2000 Hz.
; The outer loop has 40 iterations so that after 20mS, if no
additional
; pulse has been received the loop exits and the H-bridge turns off.
;
; When we exit due to a timeout we must make sure that we keep calling
; DO_MEASURE on schedule because we may be in the middle of measuring
a
; new input pulse. So we dovetail the outer loops return to idle with
; IDLE making the transistion from the PWM+Measuring state to the
; Idle+Measuring state seamless.
;
PWM:
MOVLW D'40' ; Constant for 20 mS
MOVWF OUTER_CNT ; Outer Count
MOVF PWM_CMD,W ; Set up the inner loop counters
MOVWF PWM_TMP
MOVF CMD_REG,W ; Get H-Bridge Command
MOVWF CMD_TMP ; Put it in our temporary holder
MOVWF BRIDGE_OUT ; Turn on the motors
1
MOVLW D'99' ;
1
MOVWF INNER_CNT ;
1
GOTO PWM_LOOP ; Line up command
2 (4)
PWM_LOOP:
CALL DO_MEASURE ; Do a "measurement"
16
;
; If DO_MEASURE found a pulse, it will modify the control variables ;
; PWM_TMP - Set to FF to prevent swaping CMD_REG
; INNER_CNT - Set to 1 so that this loop will exit immediately
; OUTER_CND - Set to 41 so that the outer loop will run for 20mS
; PWM_CMD - Set to the new PWM constant
; CMD_REG - Set to the new H-Bridge Command
;
DECF PWM_TMP,F ; Decrement the "On" time
1\
BTFSC ZERO_BIT ; If not zero continue
2 1
SWAPF CMD_TMP,F ; Turn off the low side
- 1
MOVF CMD_TMP,W ; Get the Command Register
1/
MOVWF BRIDGE_OUT ; Send it To the H-Bridge.
1
MOVF PWM_CMD,W ; Sort of a NOP
1
DECFSZ INNER_CNT,F ; Decrement inner loop count
1 2
GOTO PWM_LOOP ; Continue Looping
2 -
; Total Clocks (inner loop) 25 (5
uS)
;
;
; Outer loop count down, Note we've combined the MOVF PWM_CMD,W
statement
; above with the MOVWF PWM_TMP statement below to accomplish
reinitializing
; PWM_TMP in only 1 cycle. This works because the DECFSZ above doesn't
; change W. Without this trick there is no way for the outer loop to
work
; in the required 5uS and we lose the ability to call do_measure on
schedule.
;
MOVWF PWM_TMP ; Restore PWM command (loaded above)
1
CALL DO_MEASURE ; This is on a 5uS boundary.
16
MOVLW D'99' ; Reset inner loop count
1
MOVWF INNER_CNT ; Like so
1
MOVF CMD_REG,W ; Put command into W
1
MOVWF CMD_TMP ; Re-initialized CMD_TMP
1
MOVWF BRIDGE_OUT ; Send it to the motors
1
DECF OUTER_CNT ;
1
BTFSS ZERO_BIT ;
1 2
GOTO PWM_LOOP ;
2 -
;
; Getting here means we've timed out our 20 mS of looping. However we
; may be in the process of receiving a pulse so we make sure we call
; DO_MEASURE on schedule and essentially duplicate what the IDLE loop
; does and when we're done we loop to IDLE.
;
CLRF BRIDGE_OUT ; Turn off the motors
1
CALL DO_MEASURE ;
16
MOVWF TEMP ; Store result in TMP
1
MOVF TEMP,F ; Waste time, set Z bit
1
BTFSS ZERO_BIT ; If zero no new value.
2 1
GOTO PWM_LOOP ; If got a new value, then start.
- 2
GOTO $+1 ; else Waste time
2
NOP ; ...
1
GOTO IDLE ; Go back to measuring
2
;
; DO_MEASURE is the pulse measuring routine. It is called from either
; Idle or PWM. It implements a mini-state machine the monitors the
; input pin. The code is written so that it is called every 5uS.
; When called, the input will either be high or low. Depending on the
; input pins state, it either measures or doesn't.
; If the input pin is high, we start counting down our counter.
; Each count represents 5uS. If we ever underflow our counter we
; note that as a timeout (the input pulse was too wide.)
;
; If the input pin is low, we process a potential pulse. If
glitch
; is non-zero (input pulse < 860uS) we treat it as a glitch,
reset
; the counters and return. (Note this happens every time when
the
; input pin is low.)
;
; If Glitch is zero we check for a counter underflow (timeout).
If
; the counter has timed out we reset the counters and return.
(Note
; this happens every time when the input pin stays high)
;
; If we pass both of these tests (not a glitch, not a timeout)
we
; process it as a valid pulse, set all of the variables
appropriately
; and return.
;
; Given the Design, this routine _MUST_ always execute in 14 clocks.
The
; The clock counts in the right margin represent the time spent in
; various "paths" through this code.
;
DO_MEASURE:
BTFSC SERVO_IN ; Check for 'high' 2 1
GOTO INP_HIGH ; Yup, count it. - 2
(3)
MOVF GLITCH,F ; Check Glitch counter 1 -
BTFSS ZERO_BIT ; != 0 means Glitch. 2 - 1
GOTO NO_PULSE ; This was a glitch - - 2
(6)
BTFSS COUNT_HI,7 ; Check for overflow 2 - -
1
GOTO GOT_PULSE ; Process a good count - - -
2 (8)
MOVLW GLITCH_COUNT ; Glitch length 1 - -
*
MOVWF GLITCH ; Store it in GLITCH 1 - -
MOVWF COUNT_LO ; Just a glitch, 1 - -
MOVLW 1 ; Load count with constant 1 - -
MOVWF COUNT_HI ; 1 - -
RETLW 0 ; And return 2 - -
; --
; Total 14
;
;
; This is basically an abort, it resets the counters and state
variables
; and returns.
;
NO_PULSE: ; (6)
MOVLW GLITCH_COUNT ; - - 1
MOVWF GLITCH ; - - 1
MOVWF COUNT_LO ; Just a glitch, - - 1
MOVLW 1 ; Load count with 0x1A0 - - 1
MOVWF COUNT_HI ; - - 1
NOP ; To get an even 14 clocks - - 1
RETLW 0 ; And return - - 2
; --
; Total 14
;
;
; Process a "true" input.
;
INP_HIGH: ; (3)
MOVF GLITCH,F ; Check Glitch - 1
BTFSS ZERO_BIT ; Is it already 0? - 2 1
DECF GLITCH ; No, then decrement it - - 1
BTFSC COUNT_HI,7 ; Not a timeout already - 2
1
GOTO INP_TIMEOUT ; Its a timeout - -
2 (9)
MOVF COUNT_LO,F ; Test COUNT_LO for zero - 1
BTFSC ZERO_BIT ; If its zero, this is it - 2 1
DECF COUNT_HI,F ; Subtract one from COUNT_HI - - 1
DECF COUNT_LO,F ; Subtract one from the count -
1 -
RETLW 0 ; - 2
; --
; Total 14
;
;
; During a timeout condition we basically hold the state variables
; where they are so that when the pin goes low it will be detected and
; the variables reset.
;
INP_TIMEOUT: ;
(9)
NOP ; Filler to get 14 clocks - - -
1
NOP ; Filler to get 14 clocks - - -
1
NOP ; Filler to get 14 clocks - - -
1
RETLW 0 ; - - -
2
; -
-
; Total
14
;
;
; Given a valid measurement, calculate a Command and a PWM Constant.
;
; Algorithim:
; Compute Delta = Count - midpoint;
; If (Delta < 0)
; Command = Forward;
; else
; Command = Reverse;
; Delta = ABS(Delta);
; if (Delta <= DEADBAND)
; if (Delta == DEADBAND)
; Command = Coast
; else
; Command = Brake;
; PWM Constant = 100%.
; Else
; PWM Constant = Min(MAX, delta - 8) * 100/MAX.
; (for MAX == 100, this is simply (Min(MAX, delta - 8))
; Return.
;
;
GOT_PULSE: ; (8)
MOVLW D'128' ; This is the midpoint. 1
SUBWF COUNT_LO,F ; 1
BTFSS CARRY_BIT ; Carry is set (no Borrow) 2 1
GOTO DEAL_WITH_MINUS ; Figure out what to do now. - 2
(13)
POSITIVE_RESULT: ;
(+7)
MOVLW REVERSE_CMD ; Its probably reverse 1
MOVWF CMD_REG ; Store it in command register 1
NEW_PWM_VALUE: ;
(21)
MOVLW DEADBAND ; Dead band is +/- 6 (50uS) 1
SUBWF COUNT_LO,F ; Subtract DEADBAND from count. 1
BTFSS CARRY_BIT ; If no borrow, continue 2 1
GOTO DO_BRAKE ; In the dead zone do braking. - 2
(19) (26)
MOVLW D'100' ; Check if its in the range 1
SUBWF COUNT_LO,W ; Subtract 99 (max range) 1
BTFSC CARRY_BIT ; Check if its Less than MAX 2 1
GOTO MAX_PWM ; Was >= 100 - 2
(23) (30)
MOVF COUNT_LO,W ; Get count value. 1
DONE_PULSE: ; (26)
(+12)(33)
MOVWF PWM_CMD ; This is the new PWM Constant 1 1
INCF PWM_CMD ; Adjust 0 - 99 -> 1 to 100% 1 1
MOVLW 1 ; Put 1 into INNER_CNT 1 1
MOVWF INNER_CNT ; 1 1
MOVWF PWM_TMP ; 1 1
MOVWF COUNT_HI ; Reset counter 1 1
MOVLW GLITCH_COUNT ; for next time 1 1
MOVWF COUNT_LO ; 1 1
MOVWF GLITCH ; 1 1
MOVLW D'41' ; Loop count + 1 1 1
MOVWF OUTER_CNT ; 1 1
RETLW 1 ; Return true 2 2
; Totals 36 39
; Totals (max) 46
; Totals (reverse) 43 46
; Totals (do_brake) 44 51
;
; Various exit times depending on the path. Since the spec says that
; another pulse won't start for at least 5mS the results are not
; critical but they are useful to know. They become the true spec for
; the minimum separation between pulses.
;
; Max time 51 * .2 = 10.20uS, Min time 36 * .2 = 7.2uS
;
MAX_PWM:
MOVLW D'100' ; Else max (does MIN(100, val)) 1
GOTO DONE_PULSE ; Fix up loop values 2
;
; If the result was minus, it could be legitimately minus, or it could
; be that count was 0x100. We fix those by checking COUNT_HI.
;
DEAL_WITH_MINUS:
BTFSC COUNT_HI,0 ; Is bit 0 a one? 2 1
GOTO ADJUST_RESULT ; Yes, so adjust - 2
MOVLW FORWARD_CMD ; Its wider than the midpoint 1
MOVWF CMD_REG ; So this is the command. 1
COMF COUNT_LO,F ; Convert to a positive value 1
INCF COUNT_LO,F ; negate COUNT_LO 1
GOTO NEW_PWM_VALUE ; Now go compute PWM constant. 2
ADJUST_RESULT:
MOVLW D'128' ; 256 - 128 = 128 1
MOVWF COUNT_LO ; Fixup the low byte 1
GOTO POSITIVE_RESULT ; Now treat it normally. 2
;
; Now if the value is -DEADBAND thru +DEADBAND we set the command to
; "BRAKE", if it was exactly -DEADBAND or +DEADBAND we set it to
COAST.
; The reason for this is that given our sample rate/accuracy we find
that
; we get 'jitter' in the input that results in a COUNT value that can
move
; between two values on alternate samples. Given that variation, for
input
; pulse widths that are 'near' DEADBAND-1 or -(DEADBAND-1) we could
see
; alternating DEADBAND and DEADBAND-1 on the input. Without a one
value
; buffer, this causes the output to alternate between a little on (1%
PWM)
; and BRAKE. The motor then sits there and stutters. However by
defining
; the value DEADBAND exactly to be '0' the output is either COAST/ON
or
; COAST/BRAKE, both of which have a predictable and non-harmful
output.
;
DO_BRAKE:
MOVLW DEADBAND ; Restore Count Value
1
ADDWF COUNT_LO,F ; Add it back to Count
1
MOVLW DEADBAND-1 ; Check for boundary condition
1
SUBWF COUNT_LO,W ; Subtrack COUNT LO
1
BTFSC ZERO_BIT ; Check to see if its zero
2 1
GOTO ON_THE_EDGE ; Its exactly DEADBAND - 1
- 2
MOVLW BRAKE_CMD ; This is the brake Command
1 -
ON_THE_EDGE:
MOVWF CMD_REG ; Store it
1
MOVLW D'100' ; Very large PWM Constant
1
MOVWF PWM_CMD ; So we get 100% braking action
1
GOTO DONE_PULSE ; Return indicating new value
available.2 (12)
END
Thanks
Gary
gcompanion@h...
Comments
can someone help me. I am a newbe at programing, that is why I got
the BS2. I have learned alot from the manual and asking you all
questions. I am working on a digital dash for my car, well I do not
know if I want to use the stamp for it. so I thought I might try PIC
programing. but I do not know where to start. Mabe you can tell me
where to start. also how hard would it be for a newbe to do this with
a PIC:
start:
high 0
pause 250
low 0
pause 250
high 1
pause 250
low 1
pause 250
goto start
thanks
TC
there are some tutorials at the rentron site and if you need help Bruce is
always right there .
but then again so is chuck.
good luck
victor
check out some of their products it's the same as a stamp.
Original Message
From: <aconti@n...>
To: <basicstamps@yahoogroups.com>
Sent: Tuesday, May 08, 2001 5:56 PM
Subject: [noparse][[/noparse]basicstamps] PIC question
> hello all,
>
> can someone help me. I am a newbe at programing, that is why I got
> the BS2. I have learned alot from the manual and asking you all
> questions. I am working on a digital dash for my car, well I do not
> know if I want to use the stamp for it. so I thought I might try PIC
> programing. but I do not know where to start. Mabe you can tell me
> where to start. also how hard would it be for a newbe to do this with
> a PIC:
>
> start:
> high 0
> pause 250
> low 0
> pause 250
> high 1
> pause 250
> low 1
> pause 250
> goto start
>
> thanks
> TC
>
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>