PC to PIC® bi-directional Dialogue

    '     PIC Defines
    '     -----------
    @ DEVICE pic16F628, INTRC_OSC_NOCLKOUT
        ' System Clock Options    
    @ DEVICE pic16F628, WDT_ON
        ' Watchdog Timer
    @ DEVICE pic16F628, PWRT_ON
        ' Power-On Timer
    @ DEVICE pic16F628, MCLR_OFF
        ' Master Clear Options (Internal)
    @ DEVICE pic16F628, BOD_ON
        ' Brown-Out Detect
    @ DEVICE pic16F628, LVP_OFF
        ' Low-Voltage Programming
    @ DEVICE pic16F628, CPD_OFF
        ' Data Memory Code Protect
    @ DEVICE pic16F628, PROTECT_OFF
        ' Program Code Protection

    '
    '    Debug (Communication) Defines (Transmit)
    '    ----------------------------------------
    DEFINE DEBUG_REG PORTB
    DEFINE DEBUG_BIT 2
    DEFINE DEBUG_BAUD 300
    DEFINE DEBUG_MODE 1

    '
    '    DEBUG (Communication) Defines (Receive)
    '    ----------------------------------------
    DEFINE DEBUGIN_REG PORTB
    DEFINE DEBUGIN_BIT 1
    DEFINE DEBUGIN_BAUD 300
    DEFINE DEBUGIN_MODE 1

    '
    '    EEPROM Data 
    '    -----------
    '    The FIRST character of each line holds the Command Word LENGTH
    '    and the remaining 7 characters are the actual COMMAND WORD
    '    Space allocated for 10 commands although I'm only using the first five
    '    See CONSTANT CommandMax if you want to make the table larger or smaller
    '    Commands here should be in UPPERCASE although the PC can send aNyThiNg.

    '
    Data    @0,2,"ON",0,0,0,0,0
    Data    3,"OFF",0,0,0,0
    Data    5,"BLINK",0,0
    Data    5,"SWEEP",0,0
    Data    4,"BEER",0,0,0
    Data    0,0,0,0,0,0,0,0
    Data    0,0,0,0,0,0,0,0
    Data    0,0,0,0,0,0,0,0
    Data    0,0,0,0,0,0,0,0
    Data    0,0,0,0,0,0,0,0

    '
    '    RAM Assignments and Variables
    '    -----------------------------
    BadFlag var BIT            ' Flag for Bad Command
    CounterA var BYTE        ' Just a Counter
    CounterB var BYTE        ' Just a Counter
    CounterC var BYTE        ' Just a Counter
    CounterW var WORD        ' Word-sized Counter
    Command var BYTE        ' Holds the Command action to execute
    CommsBuffer var BYTE [10]    ' Max Comms Command Line size
    CommsPointer var BYTE        ' Pointer to data in Comms Buffer
    LEDStatus var BYTE
    DataA var BYTE            ' Usage as Data Byte
    Xvariable var BYTE        ' 1st Numeric Variable
    Yvariable var BYTE        ' 2nd Numeric Variable

    '
    '    Program Constants
    '    -----------------
    BufMax con 10            ' Max size of data Buffer
    CommandMax con 10        ' Max number of COMMANDS to be processed


    '
    '    Start - Initialise Processor
    '    ============================
    TRISA=%00000000
    TRISB=%00000010
    Xvariable=0:Gosub LEDsOFF    ' All LEDs OFF
    '
    '    Clear Buffer ready for start of New Command Line
    '    ------------------------------------------------
RestartLine:
    For CounterA=1 to BufMax
        CommsBuffer[CounterA-1]=0
        Next CounterA
    CommsPointer=0            ' Set Pointer to Start of Buffer
    '
    '    Communications (Closed) Loop
    '    ----------------------------
ReadLoop:
    DEBUGIN [DataA]
    If DataA<32 then 
        If DataA=8 then                 ' Process BACKSPACE Key
            If CommsPointer>0 then             ' ---------------------
                CommsPointer=CommsPointer-1    ' Rewind one position
                CommsBuffer(CommsPointer)=0    ' Erase character in Buffer
                DEBUG $08,$20,$08        ' Echo Erase sequence to PC
                Goto ReadLoop
                endif
            endif
        If DataA=13 then goto ENTERKey
        Goto ReadLoop
        endif
    If DataA>126 then goto ReadLoop
    DEBUG DataA            ' Only Echo Printable Characters
    If DataA>96 then        ' Convert all alphabetics to UPPERCASE
        If DataA<123 then DataA=DataA-32
        endif
    CommsBuffer(CommsPointer)=DataA    ' Save to Buffer
    CommsPointer=CommsPointer+1    ' Bump Pointer
    If CommsPointer<10 then goto ReadLoop
                    ' Loop for next character
    '
    '    Process [ENTER] Key
    '    -------------------
    '    also execute if Command Buffer exceeded
ENTERKey:
        '
        '    This section Parses the Command Line
        '    ====================================
            '
            '    Look for Command WORD 
            '    (scan through available Command vocabulary)
            '    -------------------------------------------
    Gosub LSpace            ' Remove Leading Blanks
    Gosub REnd            ' Locate Command Word End
    If CounterA=0 then goto EchoCRLF
                    ' Nothing to Process
    For Command=1 to CommandMax
        BadFlag=0
        CounterB=(Command-1)*8
        Read CounterB,DataA    ' Get Preset Command word Length
        If DataA=CounterA then    ' If Length correct, process entire word
            For CounterC=1 to CounterA
                CounterB=CounterB+1
                Read CounterB,DataA
                If CommsBuffer(CounterC-1)<>DataA then BadFlag=1
                Next CounterC
            If BadFlag=0 then goto GoodCommand
            endif
        Next Command
            '
            '    Bad Command Word
            '    ----------------
BadMove:
    DEBUG REP $00\8,13,10,"Bad!"
                    ' Tell User No Cigar
    
EchoCRLF:
    DEBUG 13,10            ' New Line
    Goto RestartLine        ' Loop Round and Do again

            '
            '    Scan for First Numeric Variable (if any)
            '    ----------------------------------------
GoodCommand:
    Gosub ShuffleData        ' Advance Command Line to start of next Word (if any)
    Gosub REnd            ' Locate End of next word
    Gosub GetNumericWord        ' Get numeric value
    If BadFlag=1 then goto BadMove    ' Invalid Data
    Xvariable=DataA            ' Save 1st Numeric Variable
            '
            '    Now check for 2nd Numeric Variable (if any) on the Command Line
            '    ---------------------------------------------------------------
    Gosub ShuffleData        ' Advance Command Line to start of next (last) Word (if any)
    Gosub REnd            ' Locate End of word
    Gosub GetNumericWord
    If BadFlag=1 then goto BadMove    ' Invalid Data
    Yvariable=DataA            ' Save 2nd Numeric Variable
    '
    '    Execute Command
    '    ---------------
    If (Command<4 and Xvariable>5) then
        DEBUG REP $00\8,13,10,"No such LED!"
        goto EchoCRLF
        endif
    If Command<3 then
        If Yvariable>9 then goto BadMove
        If Yvariable>1 then gosub WaitMessage
        endif
    If Command=3 then
        If Yvariable>60 then goto BadMove
        If Yvariable>5 then gosub WaitMessage
        endif
    If Command=4 then
        If Xvariable>5 then gosub WaitMessage
        endif
        '
        '    ON LED Command
        '    --------------
    If Command=1 then 
        Gosub LEDsON
        If Yvariable>0 then
            CounterW=Yvariable*1000
            Pause CounterW
            Gosub LEDsOFF
            endif
        endif
        '
        '    OFF LED Command
        '    ---------------
    If Command=2 then 
        Gosub LEDsOFF
        If Yvariable>0 then
            CounterW=Yvariable*1000
            Pause CounterW
            Gosub LEDsON
            endif
        endif
        '
        '    BLINK LED Command
        '    -----------------
    If Command=3 then
        For CounterA=1 to Yvariable
            Gosub LEDsON
            Pause 200
            Gosub LEDsOFF
            Pause 200
            Next CounterA
        endif
        '
        '    SWEEP Command
        '    -------------
    If Command=4 then
        CounterB=Xvariable
        If CounterB<1 then CounterB=1
        For CounterA=1 to CounterB
            For Xvariable=1 to 5
                Gosub LEDsON
                Pause 100
                Gosub LEDsOFF
                Next XVariable
            Next CounterA
        endif
        '
        '    BEER Command
        '    ------------
    If Command=5 then DEBUG REP $00\8,13,10,"Yes Please!"
    '
    '    Tell User all executed OK
    '    -------------------------
    DEBUG REP $00\8,13,10,"OK"
    Goto EchoCRLF

    '
    '    Subroutine Area
    '    ===============

    '
    '    Subroutine extracts Numeric Value from Command Line
    '    ---------------------------------------------------
GetNumericWord:
    DataA=0
    BadFlag=0
    If CounterA>2 then Goto BadWord
    If CounterA>0 then
        CounterB=CommsBuffer(0)
        If CounterB<48 then goto BadWord
        DataA=CounterB-48
        If DataA>9 then goto BadWord
        If CounterA=2 then
            CounterB=CommsBuffer(1)
            If CounterB<48 then goto BadWord
            CounterB=CounterB-48
            If CounterB>9 then goto BadWord
            DataA=DataA*10+CounterB
            endif
        endif
    Return
BadWord:
    BadFlag=1
    Return

    '
    '    Shuffle Data to remove processed word
    '    -------------------------------------
ShuffleData:
    For CounterB=0 to 9
        CounterC=CounterA+CounterB
        If CounterC<=9 then
            CommsBuffer(CounterB)=CommsBuffer(CounterC)
            else
            CommsBuffer(CounterB)=0
            endif
        Next CounterB
    '
    '    Subroutine removes leading SPACES (Blanks) from Buffer
    '    ------------------------------------------------------
LSpace:
    If CommsBuffer(0)=32 then
        For CounterA=1 to 9
            CommsBuffer(CounterA-1)=CommsBuffer(CounterA)
            Next CounterA
        CommsBuffer(9)=0
        Goto LSpace
        endif
    Return

    '
    '    Subroutine Locates end of Dataword in Comms Buffer
    '    --------------------------------------------------
    '    CounterA on exit End Point
REnd:    
    For CounterA=0 to 9
        If CommsBuffer(CounterA)=32 then goto REndExit
        If CommsBuffer(CounterA)=0 then goto REndExit
        Next CounterA
    CounterA=10
REndExit:
    Return

    '
    '    Subroutine tells User to Wait
    '    -----------------------------
WaitMessage:
    DEBUG REP $00\8,13,10,"Wait..."
    Return

    '
    '    Subroutine DISABLES LEDs
    '    ------------------------
LEDsOFF:
    If Xvariable=0 then
        LEDStatus=$1F
        else
        LEDStatus.0(Xvariable-1)=1
        endif
    PortA=LEDStatus
    Return

    '
    '    Subroutine ENABLES LEDs
    '    -----------------------
LEDsON:
    If Xvariable=0 then
        LEDStatus=$0
        else
        LEDStatus.0(Xvariable-1)=0
        endif
    PortA=LEDStatus
    Return

    End