Building an I2C monitor ... but i think it is not Slave....

[LakisFM1]

While speed-optimizing an IRQ Bit-bang routine i am working on now , i though it would be useful to use the EUSART Synchronous Slave Reception mode (asuming using the 2 EUSART pins of course).
Eg.

On SDA (P/N) /SCL (P only) port change Interrupt :
1. Check if STARTbit
2. If it is STARTbit then Enable the EUSART in Slave RX mode (and stay in IRQ routine ! , don't leave out!)
3. EUSART gets the 8 bit BYTE (done in hardware , no bitbanging and bit-shifting )
4. Ignore the 9th (N)ACK bit (i don't need it...)
5. Resume

6. In the next interrupt i will check if i get a STOP or a RESTART ...and so on...

I guess i am not mistaken ....

[LakisFM1]

I am happy to say that the bit-banging I2C monitor is done.

It is written all in PBP , and uses interrupts for the input-bit sensing using a...12F1822 at... 32MHz of course.

Tommorow i will post the code here , since i dont' have it now here.

Cheers!

[LakisFM1]

ASM
 __CONFIG _CONFIG1, _FOSC_INTOSC & _WDTE_ON & _PWRTE_ON & _MCLRE_OFF & _CP_OFF & _CPD_OFF & _BOREN_OFF & _CLKOUTEN_OFF & _IESO_OFF & _FCMEN_OFF
 __CONFIG _CONFIG2, _WRT_OFF & _PLLEN_ON & _STVREN_OFF & _BORV_19 & _LVP_OFF

ENDASM
 
  DEFINE OSC 32
  
    TX  VAR PORTA.0 
    SCL VAR PORTA.1 
    SDA VAR PORTA.2 

    SCLB VAR PORTAB.1
    SDAB VAR PORTAB.2
    SCLF VAR IOCAF.1
    SDAF VAR IOCAF.2
            
    BIT_COUNTER VAR BYTE
    STOP_COUNTER VAR BYTE
    BYTE_READY VAR BIT
    BYTEINT VAR BYTE
    BYTEINT2 VAR BYTE
    BYTEINB VAR BYTE
    BYTEIN VAR BYTE[30]  
    PORTAB VAR BYTE            
    BYTE_COUNTER VAR BYTE
    BYTES_RECEIVED VAR BYTE
    STOPFLAG VAR BIT

    OSCCON = %01110000         
    IOCAN = %00000100
    IOCAP = %00000110 
    
    ON INTERRUPT GoTo INT   ' Declare interrupt handler routine
 
 START:    
    PAUSE_1000
 
    OPTION_REG.7 = 1         ' DISABLE PORTB PULLUPS
       
    PORTA = %00000110        ' SWAP PORTA.0 /PORTA.2 FOR SMALL PCB
    TRISA = %00001110        ' SWAP PORTA.0 /PORTA.2 FOR SMALL PCB
    ANSELA = $00             ' MAKE ALL INPUTS DIGITAL I/O PINS
    WPUA = $00
   
    BIT_COUNTER = 0
    BYTE_COUNTER = 0
    
    INTCON = %10001000        ' Enable GLOBAL AND IOCHANGE interrupts  
    
MAIN_LOOP:
      
    IF STOPFLAG = 1 THEN   
    '/ Here we have the received bytes in the array BYTEIN(x)
    ' The size of the array is in the variable BYTES_RECEIVED.
    ' You have to process them  and then ...
    BYTE_COUNTER = 0 ' in order to get the next bytes
    ENDIF
  
    GOTO MAIN_LOOP
    
    
   
'============================================================================
'================ BIT BANGING interrupt handler  ============================
'============================================================================

Disable                                ' Don't check for interrupts in this section

INT:                                
    PORTAB = PORTA                  'Buffer the STATUS OF THE PORT
    
    '------------------------- ignore errory databits ------------------------
    'using the I2CWRITE command of PBP i got an errory SDA pulse ...
    'using the next line i ignore this error-y line ...
    'for other uses you may ommit it .

    IF SCLB = 0 THEN IOCAF = $00 : RESUME ' IGNORE WHEN CLK = 0 

    '-----------------------receive data bit -----------------------------------    
        
    if SCLF = 1 THEN                'CLK_FLAG SET : IT IS DATA !
       
    '----------------------- store byte ----------------------------------------
    
     IF BIT_COUNTER.3 = 1 THEN       ' IF WE GET 8 BITS RESET BITCOUNTER
      BIT_COUNTER.3 = 0              
   
      BYTEIN(BYTE_COUNTER) = BYTEINT ' AND STORE THE BYTE
      BYTE_COUNTER = BYTE_COUNTER + 1
   
      IOCAF.1 = 0                     ' CLEAR INT ON CHANGE FLAGS
      RESUME 
     ENDIF  
     
    ' ------------------------- receive bit ------------------------------------     
    
     BYTEINT = (BYTEINT << 1)                
     BYTEINT.0 = PORTAB.2
     BIT_COUNTER = BIT_COUNTER + 1 
         
     IOCAF.1 = 0                     ' CLEAR INT ON CHANGE FLAGS
     RESUME
    ENDIF  
  
    ' --------------------start bit-----------------------------------------------
    IF SDAB = 0 THEN 
      BIT_COUNTER = 0 
      IOCAF.2 = 0                     ' CLEAR INT ON CHANGE FLAGS
      RESUME
     ENDIF
    '---------------------stop bit ----------------------------------------------
            
      STOPFLAG = 1 
      BYTES_RECEIVED =  BYTE_COUNTER
      'BYTE_COUNTER = 0               'nevermind BYTECOUNTER WILL RESET AT THE NEXT START BIT ANYWAY
      IOCAF.2 = 0                     ' CLEAR INT ON CHANGE FLAGS
      RESUME  
ENABLE

End

[LakisFM1]

I must note i used a 12F1822 @32 MHz and the I2Cbus was running at slow speed !. I don't think the code is fast enough for a 400KHz bus!

[languer]

For those who are interested, I placed my implementation here: http://www.electro-tech-online.com/b...mitations.html