servo feed revisited
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Imagine a sewing machine. When the needle goes down, the thread is held steady and travels with the needle. When the needle goes up, the thread is fed out at the same rate that it travels up, feeding slack. There is a servo motor with an encoder feeding the thread and a matching encoder reading the travel distance and speed. There is also an aux encoder (ManDrive) that can be used to retract or feed the thread to trim or allow for excess so you can cut the thread. The manual feed/trim works as expected, but after a manual encoder change, sometimes the travel feed operates on both directions of input from the travel encoder instead of just retract. The feed is the correct direction, but when bad, the "down" feeds at twice the input rate while the "up" feeds normally. A change on the Man encoder allows it to work correctly again.
Anyone care to take another look?Code:' 1) Quadrature encoder reading direction and speed of mechanical slide. ' 2) Motor (servo) driven in ONE direction of slide movement, ' not driven for other direction. Pulse & Direction drive LOW. ' 3) Manual Encoder to drive servo either direction manually. ' ADD pull-up to GPIO.3 on 12F675 ' DEBUG splash on power-up on GPIO.5 ' 12F675 ' -----------u---------- ' -|Vdd(+) (-)Vss |- ' D_out -|GP5 GP0/PGD|- A_trav ' P_out -|GP4 GP1/PGC|- B_trav ' B_man -|GP3/MCLR/Vpp GP2/INT|- A_man ' ---------------------- DEFINE DEBUG_REG GPIO DEFINE DEBUG_BIT 5 DEFINE DEBUG_BAUD 2400 ' DEFINE DEBUG_MODE 0 DEFINE OSC 4 clear A_trav VAR GPIO.0 ' Travel encoder A input B_trav VAR GPIO.1 ' Travel encoder B input A_man var GPIO.2 ' Manual Encoder A input B_man var GPIO.3 ' Manual Encoder B input P_out var GPIO.4 ' PULSE output to motor, Active LOW D_out var GPIO.5 ' LEVEL output for direction AutoCnt var word 'preprogrammed feed @ end of cycle Dir VAR byte 'Direction EncOld var byte EncNew var byte ManCnt var byte 'Counter for recent Man Pulses TrvCnt var byte ' Travel Encoder before change INTCON = %10001000 ' GLOBAL ON, GPIO Int ON CMCON = 7 ' Comparator off, Digital I/O OPTION_REG = %00000000 ' GPIO Pull-up Enabled TRISIO = %001111 WPU = %11111111 ' weak p/u on 0-2,4,5, GPPU must be enabled for p/u IOC = %00001111 ' Interrupt on Change for GPIO: 0-3 ANSEL = 0 ' Analog off ManCnt = 0 TrvCnt = 0 P_out = 1 ' start out HI. Moves on LOW pulse INCLUDE "DT_INTS-14-0.bas" 'Base Inturrupt program:0 banks 'include "ReEnterPBP-0.pbp" 'allow PBP int ASM RBIF = GPIF RBIE = GPIE INT_LIST macro ;IntSource, Label, Type, ResetFlag? INT_Handler RBC_INT, _EncChg, ASM, yes endm INT_CREATE ;creates the INT processor INT_ENABLE RBC_INT ;enable RB change int ENDASM debug "LW-FiberDrive-7" Main: ManualDrive: ' MANUAL first: set direction bit if ManCnt > 0 then Dir = EncNew.3 ^ EncOld.2 ' XOR new L bit > Old Rt bit=Direction D_out = Dir 'set direction pin pauseus 2 P_out = 0 'send drive pulse either dir pauseus 2 P_out = 1 'reset drive pulse ManCnt = ManCnt - 1 ' empty out pulse counter endif D_out = 1 'set direction pin TravelDrive: D_out = 1 'set direction pin if TrvCnt > 0 then Dir = EncNew.1 ^ EncOld.0 ' XOR new L bit > Old Rt bit=Direction If DIR = 0 then TravDown 'end if travel DOWN pauseus 2 P_out = 0 'send drive pulse retract only pauseus 2 P_out = 1 'reset drive pulse TravDown: TrvCnt = TrvCnt - 1 endif goto main '++++++++ Motor Drive Pulse Out interrupt handler ++++++++++++++++++ EncChg: 'got here if GPIO 0-3 changed EncOld = EncNew EncNew = GPIO if (EncNew & (%00001100)) = (EncOld & (%00001100))then ' man enc same? TrvCnt = TrvCnt + 1 ' trav moved: count travel interrupts endif ManCnt = ManCnt + 1 ' else: Man moved:count man interrupts @ INT_RETURN end
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