' ==============================================================================
'
'   File...... IRB Slave.BS2
'   Purpose... Buffered serial comms with IR Buddy
'   Author.... Parallax, Inc.
'   E-mail.... stamptech@parallaxinc.com
'   Started...
'   Updated... 25 NOV 2002
'
'   {$STAMP BS2}
'   {$PBASIC 2.5}
'
' ==============================================================================


' ------------------------------------------------------------------------------
' Program Description
' ------------------------------------------------------------------------------
'
' This program waits on an eight-byte packet from a master controller.  The
' packet is checked and, if valid, the command and data are acted upon.  A
' corresponding eight-byte packet is returned to the master.
'
' Note: For best performance, shield IR Buddy from external interference


' ------------------------------------------------------------------------------
' Revision History
' ------------------------------------------------------------------------------


' ------------------------------------------------------------------------------
' I/O Definitions
' ------------------------------------------------------------------------------

IRbSIO          PIN     15                      ' IR Buddy serial I/O
LEDs            VAR     OutA                    ' LED control outputs


' ------------------------------------------------------------------------------
' Constants
' ------------------------------------------------------------------------------

IRbDataTx       CON     $44                     ' 8-byte data transmit
IRbDataRx       CON     $64                     ' 8-byte data receive

IRbMod          CON     38                      ' modulation freq: 30, 38 or 56

IRb96           CON      84 + $8000             ' 9600 baud, open
IRb48           CON     188 + $8000             ' 4800 baud, open
IRb24           CON     396 + $8000             ' 2400 baud, open
IRbBaud         CON     IRb96

STX             CON     $02
ACK             CON     $06
NAK             CON     $15

ErrHeader       CON     %0001                   ' bad header
ErrChkSum       CON     %0010                   ' bad checksum
ErrCommand      CON     %0100                   ' invalid command

LightLeds       CON     $C0                     ' commands for slave
LedsOff         CON     $C1

Busy            CON     0                       ' IR Buddy is transmitting


' ------------------------------------------------------------------------------
' Variables
' ------------------------------------------------------------------------------

buffer          VAR     Byte                    ' rx-tx buffer (8 bytes)
cmd             VAR     Byte
data1           VAR     Byte
data2           VAR     Byte
data3           VAR     Byte
data4           VAR     Byte
data5           VAR     Byte
chkSum          VAR     Byte

header          VAR     buffer                  ' rx packet
ackByte         VAR     buffer                  ' ack/nak byte
rxChkSum        VAR     Byte                    ' comparison checksum
errorLevel      VAR     Nib                     ' possible packet errors

idx             VAR     Nib                     ' loop counter


' ------------------------------------------------------------------------------
' EEPROM Data
' ------------------------------------------------------------------------------


' ------------------------------------------------------------------------------
' Initialization
' ------------------------------------------------------------------------------

Setup:
  LEDs = %0000                                  ' LEDs off
  DirA = %1111                                  ' make LED pins outputs


' ------------------------------------------------------------------------------
' Program Code
' ------------------------------------------------------------------------------

Main:
  GOSUB IR_Buddy_Reset
  SEROUT IRbSIO, IRbBaud, [IRbDataRx]           ' prep for 8-byte RX

RX_Packet:
  SERIN IRbSIO, IRbBaud, 2000, TO_Error, [STR buffer\8]
  errorLevel = %0000

Check_RX_Packet:
  IF (header = STX) THEN
    rxChkSum = chkSum                           ' save rx checksum
    GOSUB Make_CheckSum                         ' calc checksum of rx packet
    IF (rxChkSum <> chkSum) THEN                ' compare checksum values
      errorLevel = errorLevel | ErrChkSum
    ENDIF
  ELSE
    errorLevel = errorLevel | ErrHeader
  ENDIF

Process_Command:
  IF (errorLevel = 0) THEN
    SELECT cmd
      CASE LightLEDs
        LEDs = data1                            ' move data1 value to LEDs

      CASE LedsOff
        LEDs = %0000

      CASE ELSE
        errorLevel = errorLevel | ErrCommand
    ENDSELECT
  ENDIF

Make_Packet:
  IF (errorLevel = 0) THEN 
    header = ACK
  ELSE
    header = NAK
    data1 = errorLevel
  ENDIF
  GOSUB Make_CheckSum

TX_Packet:
  GOSUB IR_Buddy_Reset
  SEROUT IRbSIO, IRbBaud, [IRbDataTx, IRbMod, STR buffer\8]
  PAUSE 5                                       ' let IRB grab SIO line

TX_Wait:
  DO WHILE (IRbSIO = Busy) : LOOP               ' wait for TX to end
  GOTO Main


TO_Error:

  ' put code here that handles timeout error

  GOTO Main                                     ' reset, look for new packet

  END

' ------------------------------------------------------------------------------
' Subroutines
' ------------------------------------------------------------------------------

' Reset the IR Buddy.  This code is useful for clearing data from the RX
' buffer and prepping to switch modes.  Timing specific; do not change.

IR_Buddy_Reset:
  LOW IRbSIO                                    ' signal reset
  PAUSE 5
  INPUT IRbSIO                                  ' release reset signal
  PAUSE 50                                      ' allow time for reset actions
  RETURN


Make_CheckSum:                                  ' checksum of bytes 0 to 6
  chkSum = 0
  FOR idx = 0 TO 6
    chkSum = chkSum + buffer(idx)
  NEXT
  RETURN