'
' Project MagCard
' ===============
' Embedded Software Version 1.00
' Target Processor PIC16F628-04/SP
' Target PCB - BB-01
' Created 15/06/02
'
'

'
' Magnetic Card Reader Program
' Designed for Mag-Card Track 2
' This track contains the numeric information that
'
'
' This is a PICBASIC variation on MicroChip application
'
'
'
' Written for one LED
' LED On=Ready
' LED Off=Card Inserted
' LED Slow single Blink=Good Read
' LED multiple Rapid Blink=Bad Read
'
' MagData is a 40 byte array buffer containing all of Track 2
' the first byte (SS) is in MagData(0)
' MagError contains any Error Flags
'

'
' Device Programming Options
' --------------------------
DEVICE pic16F628, XT_OSC
' System Clock Options
DEVICE pic16F628, WDT_ON
' Watchdog Timer
DEVICE pic16F628, PWRT_ON
' Power-On Timer
DEVICE pic16F628, BOD_ON
' Brown-Out Detect
DEVICE pic16F628, MCLR_ON
' Master Clear Options (External)
DEVICE pic16F628, LVP_OFF
' Low-Voltage Programming
DEVICE pic16F628, CPD_OFF
' Data Memory Code Protect

DEVICE pic16F628, PROTECT_OFF
' Program Code Protection
'
' Hardware Assignments
' --------------------
'
' Mag Reader Connections
' ----------------------
' No Resistors required - relies on Weak Pull-Up's
'
MagRDA var PORTB.5 ' Mag-Reader Data Pin
MagCLK var PORTB.6 ' Mag-Reader Clock Pin
MagCIN var PORTB.7 ' Mag-Reader Card Loaded & Running Signal
'
' LED Connections
' ---------------
GreenLED var PORTA.4 ' 330R Resistor from Vdd via LED
' Port goes LOW for LED=ON
'
' Unused Ports
' ------------
' RA0, RA1, RA2, RA3, RA5, RA6, RA7
' RB0, RB1, RB2, RB3, RB4

'
' EEPROM Locations
' ----------------
' None used

'
' RAM Assignments and Variables
' -----------------------------
CounterA var byte ' General purpose Variable
' Used as incomming Card-Data bit counter
CounterB var byte ' General purpose Variable
' Used as byte pointer into Data Buffer
CounterC var byte ' General purpose Variable
' Used as LRC Summing character
CounterD var byte ' General purpose Variable
' Used to temporarily store incomming Card-Data bits
' and form byte ready for transfer out
'
' The four Counter variables above can be reused. Once the
' Mag-Reader program completes, they are no longer required
' However CounterB on exit holds the number of bytes in the Data buffer
'
MagData var byte [40] ' Data Array for Mag-Strip Track
' Increase this number for larger buffer size (subject
' to the maximum allowed by the PIC and PBP), but
' don't forget to also change the constant MagMax
' (below) to reflect the new buffer size.
MagError var byte ' Error Flags
' bit 7 - Used as Temporary Storage for Parity Toggle
' it is set to Zero on exit
' bit 6 - Unused
' bit 5 - Unused
' bit 4 - ES (End Sentinel) Not Found
' bit 3 - SS (Start Sentinel) Not Found
' bit 2 - Buffer Over-Run, Card Data exceeded Buffer space
' bit 1 - Parity Error
' bit 0 - LRC Error

'
' Program Constants
' -----------------
MagMax con 40 ' Max Buffer Size

'
' Start Program
' =============
' This goto below is unnescessary if you are never going to have
' any subroutines, so remove it if you wish.
'
goto JumpStart

'
' Subroutine Nest Area
' ====================
' There are no subroutines in this program
' but if there were any, put them here.

'
' End of Subroutine Nest Area
' ---------------------------

'
' Actual Start of Real Program
' ============================
JumpStart:
'
' Set Hardware Directions
' -----------------------
CMCON=%00000111 ' Disable Comparators
TRISA=%00000000 ' PORTA all set to Output
TRISB=%11111111 ' PORTB all set to Input
OPTION_REG.7=0 ' Enable Weak Pull-Ups
'
' Reset Hardware
' --------------
Pause 250 ' Timeout for Hardware to settle
'
' Zero variables ready for Card Read
' ----------------------------------
ReadReadyLoop:
For CounterA=0 to MagMax-1
' Clear Data Buffer
MagData(CounterA)=0
Next CounterA
'
' Ready to Read
' -------------
Low GreenLED ' Switch-On LED to indicate Ready to Read
While MagCIN=1:Wend ' Wait for Card to be inserted
'
' Read Card
' ---------
High GreenLED ' LED Off to indicate Card inserted
CounterB=0 ' Point to first byte in Data buffer
CounterC=0 ' Reset LRC Check byte
MagError=%00011000 ' Reset Read Error Flags
' Preset SS and ES errors (to be cleared later)
MagReadByteLoop:
CounterA=0 ' Reset for first bit of Data
CounterD=0 ' Reset holding buffer
MagError.7=0 ' Reset Temporary byte Parity Error Flag
'
' Loop for incomming Data bit
' ---------------------------
MagReadBitLoop:
If MagCIN=1 then goto MagReadErrorCheck
' Card Removed or movement stopped
If MagCLK=1 then goto MagReadBitLoop
' Loop waiting for Clock Pulse to go Low
CounterD.4=MagRDA^1 ' Read-in inverting One Card-Data Bit as we go
MagError.7=MagError.7^CounterD.4
' Toggle bit Parity for later byte Parity chaeck
CounterA=CounterA+1 ' Increment bit Counter
If CounterA<5 then
' There a 5-bits to a byte from the Card... execute
' this section if insufficient bits have been received
CounterD=CounterD>>1
' Shift bit Right one place
While MagCLK=0:Wend
' Wait for Clock to go High
Goto MagReadBitLoop
' Loop for next data bit
endif
'
' Start Bit Synchronisation
' -------------------------
'
' Synchonise incomming bits on Start Sentinel
' otherwise trash all incomming bits.
' Explanation: Until the SS byte, there could be
' an uneven and unpredictable number of bits
' in the run-up. Until the SS is recognised, all such
' bits are trashed
'
If MagError.3=1 then
' This section is only executed if SS has not
' yet been detected...
If CounterD=$0B then
MagError.3=0
' Reset SS Error Flag if SS Received
else
CounterA=CounterA-1
CounterD=CounterD>>1
' Shift Bits Right one place and trash one on the end
While MagCLK=0:Wend
Goto MagReadBitLoop
endif
endif
'
' 5th Data Bit Parity Check on received byte
' ------------------------------------------
If MagError.7<>1 then
' Parity must be odd, otherwise there's an error
MagError.1=1 ' Set Parity Error Flag
endif
'
' Save byte to main buffer and increment pointer
' ----------------------------------------------
MagData(CounterB)=CounterD
' Good or Bad, Save the data byte to buffer
'
' If you want to automatically strip-out the parity from the data,
' replace the above line with... MagData(CounterB)=CounterD&$0F
'
CounterC=CounterC^CounterD
' Add received byte for LRC Check at end
CounterB=CounterB+1 ' Increment to next byte in Data buffer
'
' Deal with LRC
' -------------
If MagError.4=0 then
' This section is executed only for the LRC
' byte following the ES...
If (CounterC&$0F)<>0 then MagError.0=1
' Test for LRC bit error
goto MagReadErrorCheck
' This is the very last valid byte, so Exit now
endif
'
' Check for End Sentinel
' ----------------------
'
' The ES (End Sentinel) signifies the end of data.
' Note that different Cards have different lengths of
' data so the ES can be anywhere in the incomming block
' of data read from the Card. Only ONE byte following
' the ES (the LRC byte) is valid. Anything following
' the LRC is considered junk and not bothered with.
'
If CounterD=$1F then MagError.4=0
' Reset ES Error Flag
' only one more time thru the loop left once flag Reset
' in order to pick up the LRC byte
'
' Check for Buffer Full
' ---------------------
If CounterB=>MagMax then
MagError.2=1 ' You should never exit here unless the Card contains
' more data than is expected (ie this is Buffer over-run)
goto MagReadErrorCheck
endif
'
' Loop around for next incomming byte
' -----------------------------------
While MagCLK=0:Wend ' Wait for Clock to go High
Goto MagReadByteLoop ' Loop for Next Data Byte

'
' Card Read Complete - Process Exit Proceedure
' ============================================

'
' Check if Good or Bad Card Read
' ------------------------------
MagReadErrorCheck:
MagError.7=0 ' Reset Temporary Parity-Count bit
If MagError<>0 then
'
' Blink LED ten times rapidly to indicate Bad Read
' ------------------------------------------------
For CounterA=1 to 10
Low GreenLED:Pause 50
High GreenLED:Pause 50
Next CounterA
else
'
' Blink LED slowly to indicate Good Read
' --------------------------------------
Pause 500:Low GreenLED:Pause 500:High GreenLED
endif
'
' At this point we have one of two possible scenario's...
'
' (1) MagError=0, There are No Errors and MagData is full of Good Data
' additionally, CounterB contains the number of data bytes held
' in MagData (these bytes include SS, ES and LRC). Also the
' Parity bit (bit 5) has NOT been stripped out in case you wanted
' the whole byte intact for your programming... see in the section
' "Save byte to buffer..." you'll find a comment indicating what to
' change if you want the parity bit removed for you.
' (2) MagError<>0. There's a problem...
' Check the flags within MagError to indicate what kind of error
' happened, and remember that MagData is probably incomplete or may
' contain corrupt or erroneous bytes.

'
' For the purposes of demonstration, all I'm going to do here is pause
' a second and then loop back to the start for another Card read.
' So you either had a single slow blink on the LED for a Good card-swipe, or
' a bunch of rapid blinks on the LED for a Bad card-swipe.
'

Pause 1000
Goto ReadReadyLoop

'
End