I2C Slave with a PIC

[tacbanon]

Hi, I'm interested to try the master-slave(I2C) worked by Daniel and other members, sorry if it is not obvious for me in the code given, but can someone share the schematic used in the example?
I'm using Pic16877(master) and Pic16F88(salve).
Thanks,
tacbanon

[tacbanon]

From the code provided, here is how I interpret the pin connection between pics.
Master(Pic16F877A) Slave(Pic16F88)
(SCL)RB5 <---> RB4
(SDA)RB7 <---> RB1
but with this connection, LCD displays "Time out", can anyone help me what I'm missing?

[aratti]

Did you pullup SCL and SDA with a 3.3K resistor?

Cheers

Al.

[tacbanon]

Hi aratti,
Thanks for replying, I added the resistors but I have the same output("Time out" on the lcd). Any idea what causing the issue?

Thanks in advance,
tacbanon

Attachment 6422

[aratti]

You should post the schematic of your setup along with the code you are using. Without more info it is difficult to give you proper answers.

Al.

[tacbanon]

Hi again,
Here is the code I'm using..
Master pic using Pic16F877A

'-------------------------------------------------------------------------------
' Master
'-------------------------------------------------------------------------------
'-------------------------------------------------------------------------------


DEFINE OSC 4


'OPTION_REG.7 = 0


ADCON1 = 7


'------------------------------------------------------------------------------


DEFINE I2C_SLOW 1


TRISB.5 = 1
TRISB.7 = 1


'------------------------------------------------------------------------------


scl VAR PORTB.5        ' i2c clock input
sda VAR PORTB.7     ' i2c data input


'------------------------------------------------------------------------------


I2Caddress VAR BYTE


valor VAR BYTE


'------------------------------------------------------------------------------


' Set LCD Data port
DEFINE LCD_DREG PORTD
' Set starting Data BIT (0 OR 4) IF 4-BIT bus
DEFINE LCD_DBIT 4
' Set LCD Register Select port
DEFINE LCD_RSREG PORTC
' Set LCD Register Select BIT
DEFINE LCD_RSBIT 6
' Set LCD Enable port
DEFINE LCD_EREG PORTC
' Set LCD Enable BIT
DEFINE LCD_EBIT 7
' Set LCD bus size (4 OR 8 bits)
DEFINE LCD_BITS 4
' Set number of lines ON LCD
DEFINE LCD_LINES 2
' Set command delay time in us
DEFINE LCD_COMMANDUS 2000
' Set Data delay time in us
DEFINE LCD_DATAUS 50


'------------------------------------------------------------------------------


Pause 500       ' Wait for LCD to startup
LCDOut $fe, 1
LCDOut $fe, "Daniel"
Pause 500       ' Wait for LCD to startup


valor = 0


'------------------------------------------------------------------------------


main:
      I2Caddress = $3


      LCDOut $fe, 1
      LCDOut "Write 1 - LED ON"
      Pause 500


      I2CWrite SDA, SCL, I2Caddress, [6], bogus ' Write offset to slave
      Pause 500


      LCDOut $fe, 1
      LCDOut "Write 1 - LED OFF"
      Pause 500


      I2CWrite SDA, SCL, I2Caddress, [8], bogus ' Write to slave
      Pause 500


      LCDOut $fe, 1
      LCDOut "Reading 1..."
      Pause 500


      I2CRead SDA, SCL, I2Caddress, [valor], bogus ' Read from slave
      LCDOut $fe, 1
      LCDOut "Value1: ", DEC valor
      Pause 500


      '--------


      I2Caddress = $5


      LCDOut $fe, 1
      LCDOut "Write 2 - LED ON"
      Pause 500


      I2CWrite SDA, SCL, I2Caddress, [4], bogus ' Write to slave
      Pause 500


      LCDOut $fe, 1
      LCDOut "Write 2 - LED OFF"
      Pause 500


      I2CWrite SDA, SCL, I2Caddress, [10], bogus ' Write to slave
      Pause 500


      LCDOut $fe, 1
      LCDOut "Reading 2..."
      Pause 500


      I2CRead SDA, SCL, I2Caddress, [valor], bogus ' Read from slave
      LCDOut $fe, 1
      LCDOut "Value2: ", DEC valor
      Pause 500


      '--------


      GoTo main       ' Do it forever


'-------------------------------------------------------------------------------


bogus:
        LCDOut $fe,1, "Time out"    ' I2C command timed out
        Pause 500


        GoTo main


'-------------------------------------------------------------------------------


End

Here is the code for the Slave Pic16F88

DEFINE OSC 8
OSCCON = 110001 '8mhz


'------------------------------------------------------------------------------


CMCON = 7
ADCON1 = 0 ' Disable A/D converter
ADCON0 = 0
ANSEL = 0 ' all analog pins to digital


'--- tris port config here (don't use SCL & SDA pins other than I2C) ----------


DEFINE I2C_HOLD 1


TRISB.1 = 1
TRISB.4 = 1

'--- Alias pins ---------------------------------------------------------------


SDADIR VAR TRISB.1
SCLDIR VAR TRISB.4


'--- Define here your variables and alias -------------------------------------


LEDT VAR PORTA.2
LEDL VAR PORTB.7
LEDM VAR PORTB.6
LEDR VAR PORTB.5
readcnt VAR BYTE
datain VAR BYTE
WrData VAR BYTE


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


SSPIF               VAR PIR1.3    ' SSP (I2C) interrupt flag
SSPIE               VAR PIE1.3 
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 SSPCON.4  ' SSP (I2C) SCK Release Control
SSPEN               VAR SSPCON.5  ' SSP (I2C) Enable
SSPOV               VAR SSPCON.6  ' SSP (I2C) Receive Overflow Indicator
WCOL                VAR SSPCON.7  ' SSP (I2C) Write Collision Detect
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 defintion ------------------------------------------------------


RxBufferLEN         CON 1       
RxBuffer            VAR BYTE[Rxbufferlen]
RxBufferIndex       VAR BYTE


'--- Tx Buffer defintion ------------------------------------------------------


TxBufferLEN         CON 1
TxBuffer            VAR BYTE[txbufferlen]
TxBufferIndex       VAR BYTE


'--- Define constants ---------------------------------------------------------


I2Caddress          CON $3 ' Make address = 3


'--- Initialize I2C slave mode ------------------------------------------------


SCLDIR = 1          ' SCL must be an input before enabling interrupts
SDADIR = 1   
SSPADD = I2Caddress ' Set our address
SSPCON = $36        ' Set to I2C slave with 7-bit address
SSPSTAT = 0
SSPIE = 1 
SSPIF = 0 
RxBufferIndex = 0
TxBufferIndex = 0


'--- Initialization Done! -----------------------------------------------------


GoTo main


'--- I2C subroutine  ----------------------------------------------------------


i2cslave:                                      ' I2C slave subroutine
          SSPIF = 0                            ' Clear interrupt flag
          IF R_W = 1 Then i2crd                ' Read data from us
          IF BF = 0 Then i2cexit               ' Nothing in buffer so exit
          IF D_A = 1 Then i2cwr                ' Data for us (not address)
          IF SSPBUF != I2Caddress Then i2cexit ' Clear the address from the buffer
          readcnt = 0                          ' Mark as first read
          GoTo i2cexit


i2cwr:                                ' I2C write data to us
       datain = SSPBUF                ' Put buffer data into array
       Rxbuffer[Rxbufferindex]=datain
       Rxbufferindex=rxbufferindex+1


       IF rxbufferindex=RxBufferLEN Then           ' end of buffer transfer 
          WrData=1
          rxbufferindex=0
       EndIF


       GoTo i2cexit


i2crd:                                      ' I2C read data from us
       IF D_A = 0 Then
          TxBufferIndex = 0
       EndIF


       While STAT_BF : Wend                        ' loop while buffer is full


       wcol = 0                                    ' clear collision flag
       SSPBUF = TxBuffer[TxBufferIndex]


       While wcol 
             wcol = 0
             SSPBUF = TxBuffer[TxBufferIndex]
       Wend


       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
             
i2cexit:
         Return


'--- End I2C subroutine  ------------------------------------------------------


Main:
     
      pause 100
      txbuffer = 12


      IF SSPIF = 1 Then
         GoSub i2cslave
      EndIF


      SSPOV = 0
      WCOL = 0


      Select Case RxBuffer[0]
             Case 6
                     High LEDT
             Case 8
                     Low LEDT
      End Select


      WrData=0  
      GoTo Main


'------------------------------------------------------------------------------


End

The codes I'm using is from Daniel(copy and paste).
BTW I'm using a simulator...

regards,
tacbanon

[aratti]

Very likely is a simulator problem!

Al.

[Address]

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