I2C Slave with a PIC

[DanPBP]

I'll try to buy a 18F2620 this week and run a few test Hope I can get it here, I live in Argentina, it's not always easy to find those "big brothers" ...

EDIT: I found a 18F452 laying around on the desk, will this serve the purpose???

[rswain]

Daniel - I'd be happy if any 18F would work. I'm starting to think something's wrong with PBP and 18F.

Thanks for your continued attempts to beat this problem into submission!

I'm going to switch to 16F877A (the old standby to see if I can get them to talk - once I get that, then we'll come back here and try again!

Robert

[DanPBP]

I played all night with a 16F88 as a master and a 16F877 as a slave (the other way around I was playing these days)...

I can send commands to the slave (16F877) and this is working fine, but something is wrong because I cannot read from the slave.

I mean, I can read from the slave, but I'm not getting the value I wanted. For example, I'm supposed to read 12, but I'm reading 1.

The code is the same I'm using for the 16F88 as a slave, so, that code is working fine. This is really strange.

PS: today is my birthday, and it's almots 7am and I need some sleep... I'll continue later in the afternoon...

[BigWumpus]

I has gone through this hell too.

I bought a cheap LA (Po.Scope) in order to debug my code. I was looking for errors in PBP too, but at least the error was im my code (and maybe in PBP)...

Please, post your code again.
I use the 16F872 and 16F876 and 18F252 as I2C-slaves. They work all !!!

Look at this page: http://www.astrosurf.com/soubie/pic_as_an_i2c_slave.htm

[DanPBP]

I saw that page and talked to Robert, but, to be honest, I don't understand how to use his code...

[BigWumpus]

Again ... post your code !

[BigWumpus]

I saw that page and talked to Robert, but, to be honest, I don't understand how to use his code...

What ?

It's PBP !

[DaveC3]

Here is the code that is working for me. I am sending three bytes to the slave. In this example 10, 20 and 30. The slave adds 1 and sends back 11, 21 and 31.

Here is a snipit of the master portion.

 I2Caddress = $0A
 I2CWrite i2cdat,i2cclk,I2Caddress,[10,20,30],NoGo
 pauseus 5
 i2cread i2cdat,i2cclk,i2caddress,[tp_x, tp_y, tp_dp],NoGo2      
 pauseus 5
    
       USBBuffer[0] = tp_x
       USBBuffer[1] = tp_y
       USBBuffer[2] = tp_dp
       USBBuffer[3] = 0
       gosub dousbout        ' I am using USB as a debugger
pause 100
goto mainmenu
NoGo:
       USBBuffer[0] = 1
       USBBuffer[1] = 2
       USBBuffer[2] = 3
       USBBuffer[3] = 0
       gosub dousbout
goto mainmenu

NoGo2:
       USBBuffer[0] = 4
       USBBuffer[1] = 5
       USBBuffer[2] = 6
       USBBuffer[3] = 0
       gosub dousbout
goto mainmenu

Here is the full slave. Pic18F2620 @ 20Mhz

asm
        __CONFIG    _CONFIG1H, _OSC_HS_1H     
        __CONFIG    _CONFIG2H, _WDT_OFF_2H & _WDTPS_512_2H
        __CONFIG    _CONFIG3H, _PBADEN_OFF_3H
        __CONFIG    _CONFIG4L, _LVP_OFF_4L & _XINST_OFF_4L
endasm
DEFINE OSC 20
'DEFINE ADC_BITS 10
'DEFINE ADC_CLOCK 3
'DEFINE ADC_SAMPLEUS 50

Define I2C_SLOW 1
DEFINE I2C_HOLD 1

'OSCCON = %01110001 '8mhz
'OSCTUNE.6 = 1  ' PLL selected 32mhz clock

' PicBasic Pro I2C slave program 
' Alias pins
scl     VAR     PORTC.3         ' I2C clock input
sda     VAR     PORTC.4         ' I2C data input

'ADCON2.7=1
ADCON1 = $F     '$B       'an1-an3 analog remainder digital
CMCON = 7         'PortA Digital
'
'---------------- Alias pins -----------------------------------

'SCLDIR              var TRISC.3 
'SDADIR              var TRISC.4

'--------------- 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 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
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
WrData              var byte
j                   var byte
'------------------- Rx Buffer defintion --------------------
RxBufferLEN         con 3           
RxBuffer            var byte[Rxbufferlen]
RxBufferIndex       var byte
RxCnt               var byte
rxcnt = 0
'------------------ Tx Buffer defintion ----------------------
TxBufferLEN         con 3
TxBuffer            var byte[txbufferlen]
TxBufferIndex       var byte
TxCnt               var byte
txcnt = 0
'------------------ Define constants ------------------------
rxinptr             var byte
rxoutptr            var byte
txinptr             var byte
txoutptr            var byte
rxinptr = 0
rxoutptr = 0
txinptr = 0
txoutptr = 0

I2Caddress          CON $0A                  ' Make address = 2

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

readcnt = 0				' Zero counter


'****************************************************************
'       Variables used in the program. 
'       
'****************************************************************

transdata              var byte
transbit7              var transdata.7
Tdata                  var word
txdata                 var word
tydata                 var word
txcomp                 var word
tycomp                 var word
tx                     var word
ty                     var word
tvalue                 var word
txcomp=0 
tycomp=0 
tx=0
ty=0
tvalue=0
PD      var            bit 'pen down flag
address var            byte

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

'SCLDIR = 1          ' SCL must be an input before enabling interrupts
'SDADIR = 1   
SSPADD = I2Caddress ' Set our address
SSPCON1 = $36        ' Set to I2C slave with 7-bit address
SSPCON2.0 = 1
SSPSTAT = 0
SSPIE = 1 
SSPIF = 0 
RxBufferIndex = 0
TxBufferIndex = 0


'LED1  var PORTC.1

    '   Interrupt definition   
    '   ====================
        '   USB interrupt used to keep USB connection alive
INCLUDE "DT_INTS-18.bas"    ' Base Interrupt System
INCLUDE "ReEnterPBP-18.bas"     ' Include if using PBP interrupts

ASM
INT_LIST  macro    ; IntSource,         Label,  Type, ResetFlag?
        INT_Handler    SSP_INT,  _I2C_Int,   PBP,  yes

    endm
    INT_CREATE               ; Creates the interrupt processor
endasm

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

@ INT_ENABLE  SSP_INT     ; Master Synchronous Serial Port Interrupt Flag bit. The transmission/reception is complete
txbuffer = 0
portc.1 = 1'high led1
goto Main
'*****************************************************************************


'------------------------- I2C subroutine  -------------------------------- 
I2C_Int:

If R_W = 0 then     'Write from master
    if D_A = 0 then  ' It's address from master
       address = SSPBUF ' do nothing
       rxcnt = 1
       rxinptr = 0
       rxoutptr = 0
       txinptr = 0
       txoutptr = 0
    else
        WCOL = 0
        sspov = 0
        if bf = 1 then   'There is data in buffer
           if rxcnt < rxbufferlen  then
              rxbuffer[rxinptr] = SSPBUF
              rxinptr = rxinptr + 1
              if rxinptr = rxbufferlen then rxinptr = 0
           endif   
           rxcnt = rxcnt + 1
           
        EndIF 
    endif
else   ' Read by master
       
        dataout = SSPBUF     'dummy read
if bf = 0 then   ' if buffer is empty
        if txcnt > 0 then  ' Is there a byte to transfer
           SSPBUF = txbuffer[txoutptr]   'get the byte abd send it
           txoutptr = txoutptr + 1       
                  if txoutptr = txbufferlen then txoutptr = 0
           txcnt = txcnt - 1
        else
        'no byte to send
        endif       
endif
endif

sspif = 0
CKP = 1 
@ INT_RETURN



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

'--------------------[ main program loop]---------------------------------------
Main:
'SSPOV = 0
'WCOL = 0
     'INTCON.7 = 0   'trrn off interrupt
     if txcnt < txbufferlen  then
          
            TxBuffer[txinptr] = rxbuffer[txinptr] | %00000001     ' add "1" to the data in
            txinptr = txinptr + 1
            if txinptr = txbufferlen  then txinptr = 0

            txcnt = txcnt + 1
            'INTCON.7 = 1   'turn on interrupt
    endif
    if rxcnt != 0 then
       datain = rxbuffer[rxoutptr]
       rxoutptr = rxoutptr + 1
       if rxoutptr = rxbufferlen  then
          rxoutptr = 0
       endif
       rxcnt = rxcnt - 1


    endif


WrData=0 



goto main 
end

Disregard all the extra stuff, I am using this slave a Touch Screen controller.

Thanks

Dave

[rswain]

Group,

I'm back using the 18F4685, one in Master and one in Slave. I'm now able to read from the Slave, 3 digits (and their even the right ones!). I set up a fast loop to read the digits on the Master side and do nothing but send the data in a fast loop on the Slave side. (Will post both sides soon).

The problem is still the same on sending data from the Master to the Slave. The address gets there, matches, sets the SSPIF and BF, but also I get the SSPOV (overflow) bit set. Even on the first attempt to read the buffer, the OV is already set. There must be some "slow it down" handshaking not happening just right. Has anyone had luck sending multiple bytes to the Slave?

rswain

[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