HI2CREAD for 18Fs

I have seen several examples of hardware I2C slaves on this forum. When I try to implement them, they never work. Most of the code is for 16F devices, which I avoid like the plague. I'm sure the problem is in front of my keyboard, but realizing that doesn't get my project working.

Is anyone willing to provide me with a block of tested code for 18Fs?

I have an 18F252 as a I2C-Slave in PBP using ASM-code for the I2C-interrupts.
OK ?

I'm happy that you have that code... Would you care to share, or is it in some 'public' place already?

I'd also love to see that. Getting my hands dirty with HW I2C isn't quite as much fun as I though it might be...

bill.

Hello,

find attached my code (2 years old and not the best!).
I have removed the maincode.
I2C reads in bytes and fills up a buffer I2C_In.
The maincode generates data in a second buffer I2C_Out.

The incoming bytes are only single bytes, I don't know if the routine will manage more than 1 data in a message.

Just read the code and try to understand the statemachine of the I2C-hardware.

Thanks! And fortunately for me - my wife speaks German!

Here is a little program that drives a LCD as a I2C slave

Code:

---

                                      *
'*  Version : 1.0                                              *
'*  Notes  : PIC 18F4550                                                  *
'*          :                                                  *
'****************************************************************
define LOADER_USED 1
define RESET_ORG 800h
define INTERRUPT_ORG 808h
DEFINE OSC 48         
     


'**** LCD *******************************************************
'Set LCD Data port
DEFINE LCD_DREG PORTA
'Set starting Data bit (0 or 4) if 4-bit bus
DEFINE LCD_DBIT 0
'Set LCD Register Select port
DEFINE LCD_RSREG PORTA
'Set LCD Register Select bit
DEFINE LCD_RSBIT 4
'Set LCD Enable port
DEFINE LCD_EREG PORTA
'Set LCD Enable bit
DEFINE LCD_EBIT 5
'LCD RW Register PORT
'DEFINE LCD_RWREG PORTB
'LCD read/write pin bit
'DEFINE LCD_RWBIT 5
'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
 
' Initialize ports and directions
ADCON1 = $F      'port A digital
CMCON = 7        'PortA Digital
' PicBasic Pro I2C slave program
' Alias pins
scl    VAR    PORTB.1        ' I2C clock input
sda    VAR    PORTB.0        ' I2C data input

' Define used register flags
SSPIF  VAR    PIR1.3          ' SSP (I2C) interrupt flag
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

' Define constants
I2Caddress CON        $A2                                ' Make our address 2

' Allocate RAM
result        VAR                BYTE                        ' ADC result
datain        VAR    BYTE                        ' Data in
dataout        VAR    BYTE[8]                        ' Data out array
readcnt        VAR    BYTE            ' I2C read count

        readcnt = 0                                ' Zero counter

pause 500
lcdout $FE,1,"    I2C LCD"
lcdout $FE,$C0,"    Ready"
trisb = %00000000
portb.0 = 0
portb.1 = 0
TRISB = %11111111
'pause 500

' Initialize I2C slave mode
        SSPADD = I2Caddress                ' Set our address
        SSPCON2 = $0                        ' General call address disabled
        SSPCON1 = $36                        ' Set to I2C slave with 7-bit address
GoTo mainloop                        ' Skip over subroutines

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

i2cwr:                                                        ' I2C write data to us
        datain = SSPBUF                        ' Put data into array
        lcdout  datain       
        GoTo i2cexit

i2crd:                                                        ' I2C read data from us
        IF D_A = 0 Then
                readcnt = 0                ' Mark as first read
        EndIF
        SSPBUF = dataout[readcnt]        ' Get data from array
        CKP = 1                        ' Release SCL line
        readcnt = readcnt + 1          ' Move along read count
        GoTo i2cexit                    ' That's it
i2cexit:
                Return
 
mainloop:                                                ' Main program loop
        IF SSPIF = 1 Then                        ' Check for I2C interrupt flag
                GoSub  i2cslave

        EndIF
        GoTo mainloop          ' Do it all forever

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I think I found this on this forum.

Thanks so much

And thanks from me as well. I'm certain I can get something working now.

Thanks for both those examples - that should help a lot.

bill.