I2C Slave with a PIC

[rswain]

Here's my slave code that's not sending back the ACK. I appologize for the "dead code" and commented out parts in advance. Maybe you'll see something I'm missing...

Robert
----------------

'Oscillator Initialization
    DEFINE OSC 32               ' Osc. in MHz
    OSCCON = %01110000          
    OSCTUNE.6 = 1               
    ADCON0.0 = 0                ' Turns off A-to-D module
    ADCON1 = $0F                ' Makes 100% port A digital 
    TRISA = %00000000
    CMCON = 7 ' Comparators Off

DEFINE I2C_HOLD 1
'DEFINE I2C_SLOW 1

' Define used register flags
SSPIF    VAR PIR1.3 ' SSP (I2C) interrupt flag
SSPIE    VAR PIE1.3 ' SSP Int Enable
BF       VAR SSPSTAT.0 ' SSP (I2C) Buffer Full
R_W      VAR SSPSTAT.2 ' SSP (I2C) Read/Write
D_A      VAR SSPSTAT.5 ' SSP (I2C) Data/Address
CKP      VAR SSPCON1.4 ' SSP (I2C) SCK Release Control
SSPEN    VAR SSPCON1.5 ' SSP (I2C) Enable
SSPOV    VAR SSPCON1.6 ' SSP (I2C) Receive Overflow Indicator
WCOL     VAR SSPCON1.7 ' SSP (I2C) Write Collision Detect
'STRETCH  VAR SSPCON2.0 ' SSP (I2C) Clock stretch

A        var byte      ' my counter variable for testing
'---------------- Alias pins -----------------------------------

TRISC.3 = 1         ' input
TRISC.4 = 1         ' input

'--------------- Define used register flags -------------------

'STAT_BF             VAR SSPSTAT.0           ' SSP (I2C) Buffer Full
'STAT_RW             VAR SSPSTAT.2           ' SSP (I2C) Read/Write
'STAT_DA             VAR SSPSTAT.5           ' SSP (I2C) Data/Address
CKE                 VAR SSPSTAT.6           ' SSP (I2C) Data/Address

'------------------- Rx Buffer definition --------------------
RxBufferLEN         con 3           
RxBuffer            var byte[Rxbufferlen]
RxBufferIndex       var byte

'------------------ Tx Buffer definition ----------------------
TxBufferLEN         con 3
TxBuffer            var byte[txbufferlen]
TxBufferIndex       var byte

'------------------ Define constants ------------------------
'I2Caddress          CON $2                  ' Make address = 2
I2Caddress          CON $06                  ' Make address = 2

' Define constants
U8       var byte
U17      var byte
InByte   var byte
OutByte  var byte
readcnt  VAR BYTE 
'U8 = $06
U17 = $08

'STRETCH = 1
WRData var byte
' Initialize I2C slave mode
'SSPCON2 = 0 ' General call address disabled

'SSPADD = My_I2C_address                     ' Set our address
SSPADD = I2Caddress                         ' Set our address
SSPCON2.7 = 0                               ' General call address disabled
SSPCON1 = $36                               ' Set to I2C slave with 7-bit address
SSPSTAT = 0
SSPIE = 1 
SSPIF = 0 
RxBufferIndex = 0
TxBufferIndex = 0
bf = 0
SSPOV = 0

    'Port C harware UART settings 
    DEFINE HSER_RCSTA 90h              
    DEFINE HSER_TXSTA 20h              
    DEFINE HSER_BAUD 9600              
    DEFINE HSER_CLROERR 1       
'----------------- Initialization Done! -----------------------------
rxbuffer[0] = 0
rxbuffer[1] = 0
rxbuffer[2] = 0

GoTo main
  

I2C_Slave:                                  ' I2C slave subroutine
  hserout ["SSPIF = ",#SSPIF,"  BF = ",#bf,13,10]
  hserout ["R_W = ",#R_w,"  D_A = ",#D_A,13,10]
  hserout ["SSPBUF = ",#SSPBUF,13,10]
  SSPIF = 0                                 ' Clear interrupt flag
  SSPov = 0                                 ' Clear interrupt flag
  bf = 0                                      ' clear buffer full
  IF R_W = 1 Then 
    hserout ["R_W = 1, Read data from U8",13,10]
    goto I2C_Read                  ' Read data from us
  endif
  IF SSPBUF = I2Caddress Then 
    hserout ["It's to me! ",#SSPBUF," = ",#I2Caddress,13,10]
  endif
  IF D_A = 1 Then 
    hserout ["Data (not address)",13,10]
    goto I2C_Write                 ' Data for us (not address)
  endif
  GoTo I2C_Exit
  
I2C_Write:                                      ' I2C write data to us
  InByte = SSPBUF                             ' Put buffer data into array
  Rxbuffer[Rxbufferindex] = InByte
  rxbufferindex = rxbufferindex + 1

  hserout ["SSPBUF Write = ",#SSPBUF,13,10]
  GoTo i2c_exit

I2C_Read:                                 ' I2C read data from us
  hserout ["SSPBUF Read = ",#SSPBUF,13,10]
  IF D_A = 0 Then
    TxBufferIndex = 0
  EndIF

while BF : wend                        ' loop while buffer is full
wcol = 0                                    ' clear collision flag
SSPBUF = TxBuffer[TxBufferIndex]
while wcol 
wcol = 0
SSPBUF = TxBuffer[TxBufferIndex]
wend
  hserout ["SSPBUF Outbyte = ",#SSPBUF," should be outbyte 16 or 31",13,10]
CKP = 1                                     ' release clock, allowing read by master
TxBufferIndex = TxBufferIndex + 1           ' increment index
if TxBufferIndex = TxBufferlen then         ' all bytes have been tx
TxBufferIndex = 0                           ' reset index            
endif
             
I2C_Exit:
Return

main:
  pause 300
  hserout [13,10,"Start of program U8",13,10]
  hserout ["RxBuffer = "]
  for a = 0 to 2
    hserout [dec rxbuffer[a],"  "]
  next a
  hserout [13,10]
loop:
'  IF SSPIF = 1 Then
  IF BF = 1 Then
    hserout [13,10,"Went into I2C_Slave routine",13,10]
    GoSub i2c_slave
    hserout ["RxBuffer = "]
    for a = 0 to 2
      hserout [dec rxbuffer[a],"  "]
    next a
    hserout [13,10]
    hserout ["SSPCON1 = ",hex sspcon1,"  ",bin sspcon1,13,10]
    hserout ["SSPCON2 = ",hex sspcon2,"  ",bin sspcon2,13,10]
    hserout ["SSPSTAT = ",hex sspstat,"  ",bin sspstat,13,10]
    hserout ["SSPBUF = ",#sspbuf,13,10]
    
    if rxbufferindex = RxBufferLEN then           ' end of buffer transfer 
      WrData = 1
      rxbufferindex = 0
      rxbuffer[0] = 0
      rxbuffer[1] = 0
      rxbuffer[2] = 0
      hserout ["RxBuffer Cleared = "]
      for a = 0 to 2
        hserout [dec rxbuffer[a],"  "]
      next a
      hserout [13,10]
    endif
  endif

  SSPOV = 0
  WCOL = 0
  IF RxBuffer[0] = 15 Then
    hserout ["Got a 15",13,10]
    hserout ["  Readcount is: ",#readcnt,13,10]
    hserout ["Have a 16 to send if asked",13,10]
    TxBuffer[0] = 16
  EndIF
  
  IF RxBuffer[0] = 30 Then
    hserout ["Got a 30",13,10]
    hserout ["  Readcount is: ",#readcnt,13,10]
    hserout ["Have a 31 to send if asked",13,10]
    TxBuffer[0] = 31
  EndIF
WrData=0  
pause 50
GoTo loop

End