I2C Slave with a PIC

[Archangel]

Interesting assumption Joe.

Al.

I mean it in context, sure there some very good professional coders in here, and when they say it I am sure it is true, now for a majority here, who likely are hobbyist, maybe some of which wish to make the jump with their own stellar idea, 50 / 50 is likely a generous assumption. And so what? EGO has value only to the person who owns it.<br>EDIT: Ego has value to anyone who wants to exert control over someone who has it too.

[ralfmayr]

Hi there,
i will test the code from Aretti soon on a PIC18F2431. I want to process four ad-converters and several digital io's. The slave address of the PIC is automatically detected when pluging it on a bus-system (16 addresses).
When it is finished and working (hope so), i will post it here.
FYI: I2C Apps from MCHIP seems not to work, a friend of me in an other company also tried this code to implement, no chance.
All others syaing "i can't post my working code here" must be sayed, that these people are wrong here, a forum lives from shared ideas, code snippets.... they should keep out here and keep their code for them selves.

Regards,
Ralf

[Charles Linquis]

I will be interested in your port to the 18F series, and it sounds like you will be willing to post your code. I have an upcoming project that will need it. I tried to get Soubie's code working about a year ago with no luck.

[ralfmayr]

Charles,
same problem, i also never got his code working.
I come back next week, hope with a working code.
Regards,
Ralf

[rswain]

Guys,

I've been working this problem for nearly a year now. I've tried Soubie's code with no luck, and the code from this thread isn't working either. I'm using the 18F4620 as the master talking to an 18F2620, the little brother of the 4620 as the slave. I've RTFM to the point I can recite it, and the Errata sheets, and I've tried countless logical, and even illogical options to trying to get it working.

The best I can get so far is the master sends the address byte and the slave accepts it when it matches its own address and ignores addresses not matching its own. When the address matches, the slave sets the Buffer Full and the Interrupt Flags, but for some reason won't send an ACK back to the master (at least that's what this thread's code [and my own polls of the master's ACK flag] are saying). I've made sure to clear all flags as the datasheet clearly directs, and still no luck. If the slave would ACK, the master would send the next byte and so on.

I'm operating both chips on their internal crystal (8 MHz) and using the 4x PLL (= 32MHz). Before you go there, I'm already successfully talking to an I2C real-time clock chip with no problems and I'm saving data to an external I2C EEPROM regularly with no problems. The I2C network is working with the PICs at 32 MHz. I'm on the right pins; I'm using the pull external pull-up resistors...

I've had this exact hardware working in the past when using MikroElektronika Basic, but I'm much happier in PBP. This one problem is holding up the entire project. Trying to get two 18F's to ping-pong data back and forth is a killer.

If someone has even a bit more success than what I've had, please post it and maybe together we can chip away at this challenge.

[DanPBP]

and the code from this thread isn't working either.

Well, the code provided by Al (aratti) and the one I posted works great both ways!

I don't know what to tell you without looking at your code, but I modified the one provided by Al just a little and worked right away!

Can you post your code? Maybe we can see something that you're not seeing.

[Charles Linquis]

I'll be able to devote some time to a group project in about two weeks. I will also have another issue - I'm forced to work with 10-bit addresses.

[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