I'm having a terrible time trying to get the I2C module on the 18F67K40 wor=
king. My test code is posted below. This code and the I2C module seem very =
simple so I must be missing something simple.=0A=
This code tries to read address 0000 of an attached 24LC512 EEPROM. I know =
the hardware is good because I can use Pic Basic Pro and read and write the=
 EEPROM using I2C.=0A=
The code I'm using came off a forum on the Microchip Support website. It is=
 "bullet proof". Ha.=0A=
=0A=
I've put debugging statements in the code and what I've found is that the I=
nterrupt flag, PIR3,SSP1IF, never gets asserted.=0A=
=0A=
Any pointers would be greatly appreciated.=0A=
=0A=
=0A=
'i2ctest.pbp=0A=
'another try at reading I2C data from 24LC512=0A=
=0A=
'Start Condition=0A=
'Control Byte for write=0A=
'High address byte=0A=
'Low address byte=0A=
'Start Condition=0A=
'Control Byte for read=0A=
'Read in data byte=0A=
'Return with NACK=0A=
'Stop Condition=0A=
=0A=
=0A=
asm=0A=
#define Memtop 0x10000       ;higest memory in the 18F67k40 processor=0A=
Startaddress =3D   MemTop-800=0A=
SDA =3D 4=0A=
SCL =3D 3=0A=
=0A=
    ORG Startaddress=0A=
=0A=
;***************************************************************=0A=
 ;=0A=
 ;  24LC256 I2C Single Byte Read Routines=0A=
 ;=0A=
 =0A=
 ;  =0A=
 ;=0A=
_I2CTEST1=0A=
    	rcall 	I2CInit=0A=
=0A=
;EE_RD	=0A=
    	rcall	I2CStrt		;send I2C START=0A=
    	movlw  h'A6'=0A=
 	rcall	I2CSend		;send device address (control byte)=0A=
   	 movlw   h'00'=0A=
 	rcall	I2CSend		;send address hi byte=0A=
   	 movlw   h'00'=0A=
 	rcall	I2CSend		;send address lo byte=0A=
 	rcall	I2CStrt		;send I2C START=0A=
   	 movlw   h'A7'=0A=
 	rcall	I2CSend		;send device address (control byte)=0A=
EE_R1	=0A=
    	rcall	I2CRcv		;receive mode (receive byte)=0A=
    	movwf   _testbyte1=0A=
 	rcall	I2CNack		;signal end of receive=0A=
 	rcall	I2CStopp		;send STOP=0A=
 	return			;=0A=
 =0A=
 ;***************************************************************=0A=
 ;=0A=
 ;  I2C primitives=0A=
 ;=0A=
 ;  SSPADD =3D ((Fosc/I2Cclock)/4)-1  {formula from AN735}=0A=
 ;=0A=
 =0A=
I2CInit	=0A=
        	bsf PIE3,SSP1IE	 ; enable the Interrupt flag, PIR3,SSP1IF=0A=
       bsf	TRISC,SCL	;=0A=
 	bsf	TRISC,SDA	;=0A=
 	movlw	b'00101000'	;SSPEN + 12C Master=0A=
 	movwf	SSP1CON1		;=0A=
 	movlw	b'00000000'	;=0A=
 	movwf	SSP1CON2		;=0A=
 	movlw	b'00000000'	;slew rate on for 400khz=0A=
 	movwf	SSP1STAT		;=0A=
 	movlw	d'13'		;(20000000/100000)-1/4=0A=
 	movwf	SSP1ADD		;400khz using 20mhz xtal 	=0A=
    return			;=0A=
=0A=
I2CDebug=0A=
   	 movf  ssp1stat,0=0A=
 	movwf _testbyte1=0A=
 	movf ssp1con1,0=0A=
 	movwf _testbyte2=0A=
 	movf ssp1con2,0=0A=
 	movwf _testbyte3=0A=
 	movf ssp1con3,0=0A=
 	movwf _testbyte4=0A=
    return=0A=
      =0A=
I2CWait	=0A=
    	btfss PIR3,SSP1IF	;complete flag?=0A=
 	bra	I2CWait		;no, wait=0A=
 	bcf	PIR3,SSP1IF	;clear irq flag=0A=
 return			;=0A=
 =0A=
I2CStrt=0A=
    	bsf	SSP1CON2,SEN_SSP1CON2	;send START condition=0A=
    	bra	I2CWait		;=0A=
     =0A=
I2CStopp	=0A=
    	bsf	SSP1CON2,PEN	;send STOP condition=0A=
 	bra	I2CWait		;=0A=
  =0A=
I2CSend=0A=
    	movwf	SSP1BUF		;send byte=0A=
 	bra	I2CWait		;=0A=
 =0A=
I2CRcv	=0A=
    	btfsc	SSP1STAT,R_W	;transmit complete?=0A=
 	bra	I2CRcv		;no, wait=0A=
 	bsf	SSP1CON2,RCEN	;receive enable=0A=
    	bcf	PIR3,SSP1IF	;clear irq flag=0A=
   	 rcall	I2CWait		;=0A=
 	movf	SSP1BUF,W	;=0A=
 return			;=0A=
 =0A=
I2CAck	=0A=
    	bcf	SSP1CON2,ACKDT	;set ACK=0A=
 	bra	I2CNack+2	;=0A=
 =0A=
I2CNack	=0A=
   	 bsf	SSP1CON2,ACKDT	;set NACK=0A=
 	bsf	SSP1CON2,ACKEN	;send ACK or NACK=0A=
 	bra	I2CWait		;=0A=
 =0A=
I2CRes	=0A=
    	bsf	SSP1CON2,RSEN	;send RESTART condition=0A=
 	bra	I2CWait		;=0A=
 =0A=
endasm=0A=
=0A=
Carey Fisher =81 Director of Engineering=0A=
O +1 770-209-0012 x2031 =81 F +1 770-209-0719=0A=
4295 Hamilton Mill Road =81 Suite 100 =81 Buford, GA 30518=0A=
www.omnimetrix.net=0A=
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Tell us how we're doing! Click here to take our two-question survey.=0A=
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