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glena
member
Joined: 25 Jul 2007
Posts: 265
Location: PA near Philly
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 Posted: Mon Jul 07, 2008 5:24 pm Post subject: Examples of Quad Decode, PID, SD File IO & a basic Sched |
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I have decided to post my code for a line follower I made.
While there are lots of basic line followers out there this one has some
advanced features that you might find useful in other projects.
I wrote this to learn how to do Quadrature Decoding and PID motor control. I also wanted to write to an SD card to log the movement and to replay the movements.
Here are some of the features:
* Use of Pin Change Interrupts for fast Quadrature Decoding
* P.I.D. motor control using the quadrature feedback and PWM
* Fat File IO to SD card for logging movement
* Basic scheduler
* Auto adapts to light levels for line following
and more...
Let me know what you think and if you have any questions on operation.
You can see pics here: http://bah.net/gallery/main.php?g2_itemId=58
Sorry, no schematic at this time...
-Glen
| Code: |
'==============================================================================
' Project: RoverX
' Created: 2007-08-05
' Edited: 2008-03-21
' By: Glen Aidukas
' Description:
' RoverX is a line Follower, Movement Logger.
' RoverX uses two geared down motors with a hall effect shaft encoders for
' feedback loop (PID).
' It is controlled by an Atmel ATmega644 8bit micro controller.
' It also has an SD/MMC attached for FAT16/32 file IO to read/write logs.
' It uses a SN754410 Quad half bridge driver for motor drive control.
'==============================================================================
'=====[ Compiler Directives ]==================================================
$crystal = 8000000 ' set via fuse bits to internal RC at 8megs
$regfile = "m644def.dat"
$baud = 38400
$hwstack = 256
$swstack = 256
$framesize = 256
'------------------------------------------------------------------------------
'=====[ Includes ]=============================================================
$include "Config_MMC.bas" ' Load SD/MMC code and config
$include "Config_AVR-DOS.BAS" ' Load FAT File system code
'------------------------------------------------------------------------------
'=====[ Aliases... ]===========================================================
M1En Alias Portd.7 ' Motor-1 Drive Enable
M1Ha Alias Portc.2 ' Motor-1 H-Bridge-A
M1Hb Alias Portc.3 ' Motor-1 H-Bridge-B
M1Qa Alias Portb.0 ' Motor-1 Quadrature Phase-A
M1Qb Alias Portb.1 ' Motor-1 Quadrature Phase-B
M2En Alias Portd.6 ' Motor-2 Drive Enable
M2Ha Alias Portc.4 ' Motor-2 H-Bridge-A
M2Hb Alias Portc.5 ' Motor-2 H-Bridge-B
M2Qa Alias Portc.0 ' Motor-2 Quadrature Phase-A
M2Qb Alias PortC.1 ' Motor-2 Quadrature Phase-B
ButtonC7 Alias Pinc.7 ' Used to initiat line following
'------------------------------------------------------------------------------
'=====[ Global Vars ]==========================================================
Dim Btemp1 As Byte ' Needed for Fat Drivers
Dim Filename As String * 14 ' Fat Filename
Dim TmpStr As String * 9 ' temp string
Dim Tick as long ' Clock tick counter
Dim Tick_Print as long ' Update Display
Dim Tick_FileIO as long ' FileIO timer
Dim Tick_UpDatePID as long ' PID Polling
Dim Tick_Movement as long ' Control Movement
Dim Tick_Look as Long ' Led sensor array update
Dim Tick_Button as Long ' Button timeout
' Motor(1&2)
Dim Kp(2) as long ' Proportional gain
Dim Ki(2) as long ' Integral gain
Dim Kd(2) as long ' Derivative gain
DIM P(2) as long ' tmp value for Proportional
DIM I(2) as long ' tmp value for Integral
DIM D(2) as long ' tmp value for Derivative
DIM previous_err(2) as long ' used in PID
Dim Scale(2) as long ' used in PID
Dim PriorErr(2) as long '
Dim IntegralErr(2) as long '
Dim PIDerr(2) as long ' Vars used in PIDpoll
Dim PIDtmp(2) as long ' Vars used in PIDpoll
Dim PIDval(2) as long ' Vars used in PIDpoll
Dim MaxSpeed(2) as integer ' Max Speed for Travel
Dim SetSpeed(2) as integer ' SetSpeed requested
Dim TargetPos(2) as Long ' Target Postion to go to
Dim CurPos(2) As Long ' Curent possition
Dim Q_NewValue(2) As Byte ' Used in Quadrature ISR
Dim Q_OldValue(2) As Byte ' Used in Quadrature ISR
Dim Q_Direction(2) As Byte ' Used in Quadrature ISR
Dim fwrite as byte ' file open/closed flag
Dim ch as byte ' junk var used for uart input
Dim x as integer ' junk var
Dim z as byte ' junk var
Dim Eye(6) as integer ' Led sensor array
Dim EyeL(6) as integer ' Low value
Dim EyeF(6) as integer ' Factor
Dim LinePos as integer ' line position
Dim LineSpeed as byte ' following speed
Dim LineFollow as Bit ' 1= follow line, 0=dont follow.
Dim DebugFlag as Bit ' 1= print debug info
'------------------------------------------------------------------------------
'=====[ Constants ]============================================================
Const Next_Tick_Print = 500
Const Next_Tick_FileIO = 100
Const Next_Tick_UpDatePID = 10
Const Next_Tick_Movement = 50
Const Next_Tick_Look = 50
Const Next_Tick_Button = 500
Const LineSpeedMax = 25
'------------------------------------------------------------------------------
'=====[ Routine declarations ]=================================================
Declare Sub PIDPoll ' This is the main PID code
Declare Sub PrintDebug ' Print out the uart some of the current values
Declare Sub LogIt ' Write log data to the SD/MMC card
Declare Sub ProcessCMD ' Process commands from uart
Declare Sub MovenentControl ' Process movement
Declare Sub Look ' Read LED Sensor Array
Declare Sub LineFollowCMD ' Turn on/off line following
Declare Sub OpenLogFile ' Open file for logging
'------------------------------------------------------------------------------
'=====[ Set IO Pins ]==========================================================
''' set data direction registors for io pins
DDRa = &B00000000 ' bits 1-6 are used for LED sensors
' bits 0&7 not used
DDRB = &B10110000
' bits 0 & 1 are for M1 quadrator(a&b) position ticks
' bits 2&3 not used
' bit 4 - SD/MMC CS (DDIR is reset by Config_MMC.bas)
' bit 5 - SD/MMC MOSI (DDIR is reset by Config_MMC.bas)
' bit 6 - SD/MMC MISO (DDIR is reset by Config_MMC.bas)
' bit 7 - SD/MMC SCK (DDIR is reset by Config_MMC.bas)
DDRC = &B00111100
' bits 0 & 1 are for M2 quadrator(a&b) position ticks
' bits 2-5 used for Motor (M1& M2) direction control
' bit 6 not used, bit 7 used for button
DDRD = &B11000000
' bits 0&1 used by uart0
' bits 2&3 not used (future uart1)
' bits 4&5 not used
' bit 6 M2 drive enable
' bit 7 M1 drive enable
PortC.7 = 1 ' turn on resistor pullup for button
'------------------------------------------------------------------------------
'=====[ Setup Timer1 for Tick isr ]============================================
''' Timer1 is used for Tick counter
Config Timer1 = Timer , Prescale = 8 , Compare A = Disconnect , Clear Timer = 1
' crystal / Prescale / CountWanted = reload value
' 8000000 / 8 / 1000 = 1000 (trigger ever 1000th sec)
Compare1a = 1000
On Compare1a T1_TickCounter_isr
Enable Timer1
Enable Compare1a
'------------------------------------------------------------------------------
'=====[ Config Timer2 for Motor PWM power Control ]============================
' Timer2 is used for motor power control on M1 & M2
' This is done by using the PWM out puts on Timer2 (OC2A and OC2B) and
' connecting them to the Enable inputs on the H-Bride that drives the motors.
Config Timer2 = Pwm , Compare A Pwm = Clear Down , Compare B Pwm = Clear Down , Prescale = 1
Pwm2a = 0 ' Set initial speed to 0
Pwm2b = 0 ' Set initial speed to 0
'------------------------------------------------------------------------------
'=====[ Enable Pin change interrupt ]==========================================
' The Pin Change Interupts are used for the quadrature imputs from the motors.
Pcmsk1 = &B0000011 ' Set mask for pcint1 (PortB.0&1)
Pcmsk2 = &B0000011 ' Set mask for pcint2 (PortC.0&1)
Pcicr.1 = 1 ' Enable Pcint1 (Pin Change Interrupt)
Pcicr.2 = 1 ' Enable Pcint2 (Pin Change Interrupt)
On Pcint1 M1Quad_count_isr ' Set interrupt vector for PCINT1
On Pcint2 M2Quad_count_isr ' Set interrupt vector for PCINT2
'------------------------------------------------------------------------------
'=====[ Setup ADC ]============================================================
''' ADC1-6 are used for LED sensors
Config Adc = Single , Prescaler = Auto , Reference = Avcc
Start Adc
'------------------------------------------------------------------------------
'=====[ Config misc stuff ]====================================================
Config Serialout = Buffered , Size = 254 ' Serial Buffering
' setup default gains for the PID rutine
Kp(1) = 128 : Kp(2) = Kp(1)
Ki(1) = 30 : Ki(2) = Ki(1)
Kd(1) = 196 : Kd(2) = Kd(1)
Scale(1) = 8 : Scale(2)= Scale(1)
' setup timer off sets for the sub rutines.
' the lower the number the higher the priority
Tick_UpDatePID = 0
Tick_Movement = 1
Tick_FileIO = 2
Tick_Look = 4
Tick_Print = 3
Tick_Button = 5
for z = 1 to 6 ' set the initial optic values...
EyeL(z) = 1000
EyeF(z) = 1
next z
Enable Interrupts
'------------------------------------------------------------------------------
print chr(27) ; "[2J"; ' ansi clear screen...
print "Starting..."
waitms 300
'******************************************************************************
'*****[ Start of main loop ]***************************************************
'******************************************************************************
do
select case Tick
case is > Tick_UpDatePID : Gosub PIDPoll ' update PID
case is > Tick_FileIO : Gosub LogIt
case is > Tick_Print : Gosub PrintDebug
case is > Tick_Movement : Gosub MovenentControl
case is > Tick_Look : Gosub Look
case else :
if ButtonC7 = 0 then Gosub LineFollowCMD
if ISCHARWAITING() = 1 then Gosub ProcessCMD
end select
Loop
End
'^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
'^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
'=====[ PrintIt routine ]======================================================
''' Send out the uart some curent internal values
Sub PrintDebug
portd.5 = 0
if DebugFlag = 1 then
print chr(27) ; "[1;1H"; ' Move to top of page
Print "Tick: " ; Tick
print
print "TargetPos: " ; TargetPos(1) ; ", " ; TargetPos(2) ; " "
print "CurPos : " ; CurPos(1) ; ", " ; CurPos(2) ; " "
print "PIDerr : " ; PIDerr(1) ; ", " ; PIDerr(2) ; " "
print "PriorErr : " ; PriorErr(1) ; ", " ; PriorErr(2) ; " "
print "P : " ; P(1) ; ", " ; P(2) ; " "
print "I : " ; I(1) ; ", " ; I(2) ; " "
print "D : " ; D(1) ; ", " ; D(2) ; " "
print "PIDval(a&b): " ; PIDval(1) ; ", " ; PIDval(2) ; " "
print "Kp : " ; Kp(1) ; " "
print "Kd : " ; Kd(1) ; " "
print "Ki : " ; Ki(1) ; " "
print "Scale: " ; Scale(1) ; " "
print "Speed: " ; SetSpeed(1) ; " "
print "write: " ; fwrite
' print "Eyes: " ;
' print Eye(1);",";Eye(2);",";Eye(3);",";Eye(4);",";Eye(5);",";Eye(6);" "
' Print "LinePos: " ; LinePos ; " "
' Print "LineFollow: " ; ButtonC7 ; " , " ; LineFollow ; " "
' print "LineSpeed: " ; LineSpeed ; " "
endif
Tick_Print = Tick_print + Next_Tick_Print
portd.5 = 1
end sub
'------------------------------------------------------------------------------
'=====[ Process Commands routine ]=============================================
''' Check for chars from uart and process them
Sub ProcessCMD
ch = inkey()
if ch <> 0 then
SELECT CASE ch
Case "P" : ' incrament P factor
Incr Kp(1) : Incr Kp(2)
Case "p" : ' decrament P factor
Decr Kp(1) : Decr Kp(2)
Case "I" : ' incrament I factor
Incr Ki(1) : Incr Ki(2)
Case "i" : ' decrament I factor
Decr Ki(1) : Decr Ki(2)
Case "D" : ' incrament D factor
Incr Kd(1) : Incr Kd(2)
Case "d" : ' decrament D factor
Decr Kd(1) : Decr Kd(2)
Case "S" : ' increase scale
Incr Scale(1) : Incr Scale(2)
Case "s" : ' decrease scale
Decr Scale(1) : Decr Scale(2)
Case ")" : ' increase set speed
Incr SetSpeed(1) : Incr SetSpeed(2)
Case "(" : ' decrease set speed
Decr SetSpeed(1) : Decr SetSpeed(2)
Case "o" : ' Stop!
SetSpeed(1) = 0 : SetSpeed(2) = 0
Case "+" : ' move forward one tick position
Incr TargetPos(1) : Incr TargetPos(2)
Case "-" : ' move back one tick position
Decr TargetPos(1) : Decr TargetPos(2)
Case "]" : ' + 10
TargetPos(1) = TargetPos(1) + 10
TargetPos(2) = TargetPos(2) + 10
Case "[" : ' -10
TargetPos(1) = TargetPos(1) - 10
TargetPos(2) = TargetPos(2) - 10
Case "}" : ' +100
TargetPos(1) = TargetPos(1) + 100
TargetPos(2) = TargetPos(2) + 100
Case "{" : ' -100
TargetPos(1) = TargetPos(1) - 100
TargetPos(2) = TargetPos(2) - 100
Case "." : ' turn left (one tick)
TargetPos(1) = TargetPos(1) + 1
TargetPos(2) = TargetPos(2) - 1
Case "," : ' turn right (one tick)
TargetPos(1) = TargetPos(1) - 1
TargetPos(2) = TargetPos(2) + 1
Case ">" : ' turn right (5 ticks)
TargetPos(1) = TargetPos(1) + 5
TargetPos(2) = TargetPos(2) - 5
Case "<" : ' turn left (5 ticks)
TargetPos(1) = TargetPos(1) - 5
TargetPos(2) = TargetPos(2) + 5
case "1" :
decr TargetPos(1)
case "2" :
decr TargetPos(1) : decr TargetPos(2)
case "3" :
decr TargetPos(2)
case "4" :
decr TargetPos(1) : incr TargetPos(2)
case "5" :
'
case "6" :
incr TargetPos(1) : decr TargetPos(2)
case "7" :
incr TargetPos(1)
case "8" :
incr TargetPos(1) : incr TargetPos(2)
case "9" :
decr TargetPos(2)
case "0" :
TargetPos(1) = 0 : TargetPos(2) = 0
CurPos(1) = 0 : CurPos(2) = 0
case " " : ' reset positions to 0
TargetPos(1) = 0 : TargetPos(2) = 0
CurPos(1) = 0 : CurPos(2) = 0
SetSpeed(1) = 0 : SetSpeed(2) = 0
print chr(27) ; "[2J";
case "c" : ' clear the screen
print chr(27) ; "[2J";
Case "z" : DebugFlag = 1
Case "Z" : DebugFlag = 0
Case "W" : ' open fie for writing...
Gosub OpenLogFile
case "w" : ' close file
print #10, "Closing..."
close #10
fwrite = 0
End Select
end if
end sub
'------------------------------------------------------------------------------
'=====[ LogIt routine ]========================================================
''' Write data to the SD/MMC card
Sub LogIt
if fwrite = 1 then
print #10, Tick;",";TargetPos(1);",";TargetPos(2);",";CurPos(1);",";CurPos(2)
endif
Tick_FileIO = Tick_FileIO + Next_Tick_FileIO
end sub
'------------------------------------------------------------------------------
'=====[ Timer ISR routine ]====================================================
T1_TickCounter_isr:
Incr Tick
Return
'------------------------------------------------------------------------------
'=====[ M1 Quadrature ISR routine ]============================================
M1Quad_count_isr:
Q_NewValue(1) = Pinb
Q_Direction(1) = Q_OldValue(1).0 Xor Q_NewValue(1).1
If Q_Direction(1) = 1 Then
Incr CurPos(1)
Else
Decr CurPos(1)
End If
Q_OldValue(1) = Q_NewValue(1)
Return
'------------------------------------------------------------------------------
'=====[ M2 Quadrature ISR routine ]============================================
M2Quad_count_isr:
Q_NewValue(2) = Pinc
Q_Direction(2) = Q_OldValue(2).0 Xor Q_NewValue(2).1
If Q_Direction(2) = 1 Then
Incr CurPos(2)
Else
Decr CurPos(2)
End If
Q_OldValue(2) = Q_NewValue(2)
Return
'------------------------------------------------------------------------------
'=====[ PID polling routine]===================================================
''' Motor PID Control.........................................................
Sub PIDPoll
dim tmp as long
dim Itmp as long
For z = 1 to 2
''' set Proportional P = (Target - CurPos) * Kp
PIDerr(z) = TargetPos(z) - CurPos(z)
P(z) = PIDerr(z) * Kp(z)
''' set Integral I = I + (error * Ki)
tmp = PIDerr(z) * Ki(z)
I(z) = I(z) + tmp
If I(z) > 10230 then I(z) = 10230 ' limit windup
If I(z) < -10230 then I(z) = -10230
if PidErr(z) = 0 then
if I(z) > 0 then I(z) = I(z) - 1
if I(z) < 0 then I(z) = I(z) + 1
endif
Itmp = I(z) / 10
''' set Derivative D = (error - previous_error) * Kd
tmp = PIDerr(z) - PriorErr(z)
D(z) = tmp * Kd(z)
''' PIDval = P - I + D / scale
' PIDval(z) = P(z) + I(z)
PIDval(z) = P(z) + Itmp
PIDval(z) = PIDval(z) + D(z)
PIDval(z) = PIDval(z) / scale(z)
PriorErr(z) = PIDerr(z)
''' Set Limits
if PIDval(z) > 255 then
PIDval(z) = 255
elseif PIDval(z) < -255 then
PIDval(z) = -255
endif
Next z
''' Set Motor Direction and PWM for motor 1
if PIDval(1) > 0 then
M1Ha = 1 : M1Hb = 0 ' Set h-bridge to go farward
PWM2a = PIDval(1)
end if
if PIDval(1) < 0 then
M1Ha = 0 : M1Hb = 1 ' Set h-bridge to go backwards
PWM2a = -PIDval(1) ' invert pwm value
end if
if PIDval(1) = 0 then ' Set h-bridge to Coast
M1Ha = 0 : M1Hb = 0
PWM2a = 0
end if
''' Set Motor Direction and PWM for motor 2
if PIDval(2) > 0 then
M2Ha = 1 : M2Hb = 0 ' Set h-bridge to go farward
PWM2b = PIDval(2)
end if
if PIDval(2) < 0 then
M2Ha = 0 : M2Hb = 1 ' Set h-bridge to go backwards
PWM2b = -PIDval(2) ' invert pwm value
end if
if PIDval(2) = 0 then ' Set h-bridge to Coast
M2Ha = 0 : M2Hb = 0
PWM2b = 0
end if
Tick_UpDatePID = Tick_UpDatePID + Next_Tick_UpDatePID ' next pid update
end sub
'------------------------------------------------------------------------------
'=====[ Control Movement routine ]=============================================
Sub MovenentControl
' line following..
if LineFollow = 1 then
TargetPos(1) = TargetPos(1) + LineSpeed
TargetPos(2) = TargetPos(2) + LineSpeed
x = abs(LinePos)
if LinePos < 0 then ' Turn left
TargetPos(1) = TargetPos(1) - x
TargetPos(2) = TargetPos(2) + x
endif
if LinePos > 0 then 'Turn right
TargetPos(2) = TargetPos(2) - x
TargetPos(1) = TargetPos(1) + x
endif
else
TargetPos(1) = TargetPos(1) + SetSpeed(1)
TargetPos(2) = TargetPos(2) + SetSpeed(2)
endif
Tick_Movement = Tick_Movement + Next_Tick_Movement
end sub
'------------------------------------------------------------------------------
'=====[ Line Following routine ]===============================================
Sub LineFollowCMD
''' Toggle line following mode (on/off)
if Tick < Tick_Button then return
While ButtonC7 = 0
Wend
If LineFollow = 0 then
SetSpeed(1) = 0
SetSpeed(2) = 0
LineFollow = 1
else
SetSpeed(1) = 0 : SetSpeed(2) = 0
TargetPos(1) = 0 : TargetPos(2) = 0
CurPos(1) = 0 : CurPos(2) = 0
M1Ha = 0 : M1Hb = 0 : PWM1b = 0
M2Ha = 0 : M2Hb = 0 : PWM2b = 0
LineFollow = 0
endif
Tick_Button = Tick + Next_Tick_Button ' Don't listen until some time passes.
end sub
'------------------------------------------------------------------------------
'=====[ Look at LED array ]====================================================
Sub Look
''' get the LED(1-6) values and auto adjust for new lows and highs
for z = 1 to 6
Eye(z) = Getadc(z)
if Eye(z) < EyeL(z) then ' we have a new low....
EyeL(z) = Eye(z)
endif
Eye(z) = Eye(z) - EyeL(z) ' zero adjust for proper low.
x = Eye(z) / EyeF(z) ' ajust for the high value
if x > 25 then ' we have a new high...
EyeF(z) = Eye(z) / 25
endif
Eye(z) = Eye(z) / EyeF(z) ' ajust for the high value
next z
''' Set speed based on quality and possition of line
x = Eye(3)
x = x + Eye(4)
x = x * 4
x = x + Eye(2)
x = x + Eye(5)
x = x / 3
x = x + 5
LineSpeed = LineSpeed + x
LineSpeed = LineSpeed / 3
if LineSpeed > LineSpeedMax then LineSpeed = LineSpeedMax
''' get the line possition (left to right)
''' adjust weight based on how far from center the line is
LinePos = 0
x = Eye(1) * -2 : LinePos = LinePos + x
x = Eye(2) * -1 : LinePos = LinePos + x
x = Eye(3) * -1 : LinePos = LinePos + x
x = Eye(4) * 1 : LinePos = LinePos + x
x = Eye(5) * 1 : LinePos = LinePos + x
x = Eye(6) * 2 : LinePos = LinePos + x
LinePos = LinePos / 7
Tick_Look = Tick_Look + Next_Tick_Look
end sub
'------------------------------------------------------------------------------
'=====[ Open file for logging ]================================================
Sub OpenLogFile
Btemp1 = Initfilesystem(1) ' Init Partition 1
If Btemp1 <> 0 Then
Print "Error: " ; Btemp1 ; " at Init file system"
Else
' look for an unused filename...
z = 0 : x = 0
while z = 0
Filename = "000" + str(x)
TmpStr = Right(Filename, 3)
Filename = "RvrX-" + TmpStr + ".log"
Open Filename For Input As #10
if EOF(#10) <> 0 then z = 1
close #10
incr x
if x > 999 then
print "To many files!!!!!"
return
endif
wend
print "Filename: " ; Filename
Open Filename For Output As #10
print #10, "Tick,TargetPos(1),TargetPos(2),CurPos(1),CurPos(2)"
fwrite = 1
endif
end sub
'------------------------------------------------------------------------------
end
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WanaGo
member
Joined: 15 Aug 2008
Posts: 111
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| Posted: Wed Sep 10, 2008 9:57 am Post subject: |
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Hello,
I am just trying to get my head around the code used for quadrature encoder inputs.
I have looked through your code and see this section, which appears to be the main setup for the quadrature input pins
'=====[ Enable Pin change interrupt ]==========================================
' The Pin Change Interupts are used for the quadrature imputs from the motors.
Pcmsk1 = &B0000011 ' Set mask for pcint1 (PortB.0&1)
Pcmsk2 = &B0000011 ' Set mask for pcint2 (PortC.0&1)
Pcicr.1 = 1 ' Enable Pcint1 (Pin Change Interrupt)
Pcicr.2 = 1 ' Enable Pcint2 (Pin Change Interrupt)
On Pcint1 M1Quad_count_isr ' Set interrupt vector for PCINT1
On Pcint2 M2Quad_count_isr ' Set interrupt vector for PCINT2
'------------------------------------------------------------------------------
I see above this there was setting up the pins as inputs etc.
Question, where abouts in the help is there about the PCMSK and PCINT and PCICR etc?
I cant seem to find much about it, or that it even existed.
Can you tell me what the PCICR is?
I read in the help on the READHITAG topic, this:
| Quote: | | When you use the PCINT interrupt it is important to realize that other pins must be masked off. The PCMSK register may have only 1 bit enabled. Otherwise there is no way to determine which pin was changed. |
but that is about all I can find on the topic.
Basically I am wanting to find any help about setting pins up to work to read a quadrature input, and how you set them to read the 'pin change' style input.
What you have written in the ISR etc is all fine, its just the setting up of the actual pins and interrupt I am having problems with.
Thanks in advance
James |
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pseddon
member
Joined: 20 Oct 2006
Posts: 75
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| Posted: Thu Sep 11, 2008 2:19 pm Post subject: |
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The function of PCMSK etc. can be found in the chip data sheet.
regards Peter |
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glena
member
Joined: 25 Jul 2007
Posts: 265
Location: PA near Philly
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| Posted: Sat Sep 13, 2008 4:27 am Post subject: |
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James (WanaGo),
The main issue I had when first trying to understand how to use pin change interrupts is to first note that there is not one interrupt for each pin but rather there are only 4 separate interrupts (one per port). So you first need to select the pins on a given port (using the Pcmsk0, 1, 2 or 3) for the given pins you want to get an interrupt for.
In: Pcmsk1 = &B0000011 I am saying on PortB, pins 0 & 1 are going to trip the interrupt (Pcint1).
If you are using more then one pin on a given port then you will need to test for what pin actually changed on that port when you get the interrupt. Once the mask is set for all the pins you want to use you then need to turn on the interrupt for the port that the pins are connected to. You do this with the PCICR register. Bit 0 for porta, bit 1 for portb and so on. Lastly you need to setup the interrupt vector via the "On Pcint1 M1Quad_count_isr" statement.
In the example I have there are actually 4 pins total that I need to get an interrupt on. I could have put them all on one port but since I don't know when the the pulses are going to come in, I separated the two different AB signals from the first motor and AB from the second motor. Since A & B can not happen at the same moment they can share the interrupt. I then test use their state to determine the state (up or down).
Note that I only test for two possible states out of four. Up, Down, NoChange and ErrorState. As long as the encoder out put is clean and not so fast that the ISR cant keep up then the only states you should get interrupts for are Up or Down. I don't remember what speed I tested the code to but it was error free to the fasted speed I was able to push the motors too.
I hope this helps. 
Let me know if you have any other questions...
-Glen |
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dbrother
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Joined: 07 Jan 2007
Posts: 7
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| Posted: Thu Jan 22, 2009 3:38 am Post subject: |
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| thank u very much! |
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