Using SPI with External Interrupts

[shaiqbashir]

hi guys!

im making a project that has two PIC18f452. one pic is acting as SPI master, the other is acting as SPI slave. The master makes portB.0 of SPI slave low which it takes as INT0 interrupt. then master sends "?" through SPI, in return slave has to send "!" after which the master will send its data through SPI to slave. before using external interrupt(INT0), the SPI communication was working well. But when i enabled this interrupt, the slave is not sending the "!" to the master as a result master is unable to send its data to slave through SPI. Here is my coding of master:

Include "Modedefs.Bas"

DEFINE HSER_RCSTA 90h 
DEFINE HSER_TXSTA 24h 
DEFINE HSER_BAUD 9600
DEFINE HSER_SPBRG 25

define OSC 4

DEFINE ADC_BITS 8       ' Set number of bits in result
DEFINE ADC_CLOCK 2     ' Set clock source (rc = 3)
DEFINE ADC_SAMPLEUS 50 ' Set sampling time in microseconds 
 
' Set LCD Data port
DEFINE LCD_DREG PORTD
' Set starting Data bit (0 or 4) if 4-bit bus
DEFINE LCD_DBIT 0
' Set LCD Register Select port
DEFINE LCD_RSREG PORTC
' Set LCD Register Select bit
DEFINE LCD_RSBIT 0
' Set LCD Enable port
DEFINE LCD_EREG PORTC
' Set LCD Enable bit
DEFINE LCD_EBIT 1
' Set LCD bus size (4 or 8 bits)
DEFINE LCD_BITS 8
' 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

SSPEN	VAR		SSPCON1.5	'SSP Enable bit
CKP		VAR		SSPCON1.4	'Clock Polarity Select
SMP		VAR		SSPSTAT.7	'Data input sample phase
CKE		VAR		SSPSTAT.6	'Clock Edge Select bit
SSPIF	VAR		PIR1.3		'SPI interrupt flag

i		VAR		BYTE		'loop counter
a		VAR		byte[6]		'Holds 6 characters read from slave
b		VAR		byte[6]		'Holds 6 characters read from slave
c       var     byte[6]     'Holds 6 characters read from slave

        ADCON1 = 7			'Set PORTA and PORTE to digital
        Low PORTE.2			'LCD R/W line low (W)
        Pause 100			'Wait for LCD to start up

		TRISC = %10010000	'set PORTC I/O
		
		SSPEN = 1			'enable SPI pins
		CKP = 0				'clock idle low
		CKE = 0				'transmit on idle to active transition
		SSPIF = 0			'clear buffer full status
		SMP = 0				'sample in middle of data
	SSPCON1.0 =  0
    SSPCON1.1 =  0
    SSPCON1.2 =  0
    SSPCON1.3 =	 0
		
loop:
        high portB.0
        HSERIN [WAIT("a"),STR a\4\"\"]
        pause 50
        hserout["ok",13,10]
		pause 50
		HSERIN [WAIT("a"),STR b\4\"\"]
        pause 50
        hserout["ok",13,10]
		pause 50
		HSERIN [WAIT("a"),STR c\4\"\"]
        pause 50
        hserout["ok",13,10]
		pause 50
		low portB.0
        GoSub senddata		'initiate conversion and receive data
		GoTo loop			'do it forever
		
senddata:					
		SSPBUF = "?"					'send ? to start conversion
		hserout["? sent",13,10]
        GoSub letclear					'wait for buffer to clear
		IF SSPBUF<>"!" Then senddata		'wait for reply (!)
        
		For i = 0 to 4		'loop for 6 characters
			SSPBUF = 0		'write to SSPBUF to start clock
			GoSub letclear	'wait for receipt
			SSPBUF=a[i]	    'store received character in array
		Next i				'get next character
        
		For i = 0 to 4		'loop for 6 characters
			SSPBUF = 0		'write to SSPBUF to start clock
			GoSub letclear	'wait for receipt
			SSPBUF=b[i]	    'store received character in array
		Next i
		
        For i = 0 to 4		'loop for 6 characters
			SSPBUF = 0		'write to SSPBUF to start clock
			GoSub letclear	'wait for receipt
			SSPBUF=c[i]	    'store received character in array
		Next i
        
        Return

letclear:

		IF SSPIF = 0 Then letclear	'wait for SPI interupt flag
		PauseUs 25					'25uS fudge factor
		SSPIF = 0					'reset flag
		Return

and here is my coding for the slave:

Include "Modedefs.Bas"

DEFINE HSER_RCSTA 90h 
DEFINE HSER_TXSTA 24h 
DEFINE HSER_BAUD 9600
DEFINE HSER_SPBRG 25

define osc 4

DEFINE ADC_BITS 8       ' Set number of bits in result
DEFINE ADC_CLOCK 8     ' Set clock source (rc = 3)
DEFINE ADC_SAMPLEUS 50 ' Set sampling time in microseconds 

dataout	 VAR    BYTE[8]			'Data out array
dataout2 var    byte[8]
dataout3 var    byte[8]

SSPEN	 VAR	SSPCON1.5		'SSP Enable bit
CKP		 VAR	SSPCON1.4		'Clock Polarity Select
SMP		 VAR	SSPSTAT.7		'Data input sample phase
CKE		 VAR	SSPSTAT.6		'Clock Edge Select bit
SSPIF	 VAR	PIR1.3			'interrupt flag - last bit set

SCL    	 Var    PortB.6         ' I2C data pin
SDA      Var    PortB.7         ' I2C clock pin

i		        VAR	   BYTE			'loop counter
a		        VAR	   BYTE[6]			'Holds 6 characters of data
addr            var    word
E_ByteOut      	Var    Byte		' Data byte to be written to the Eeprom
E_ByteIn	    Var	   Byte
b               var    byte
c               var    byte

Define	I2C_SCLOUT	1

on interrupt goto DECIDE
INTCON.7=1
INTCON.6=1
INTCON.4=1
INTCON2.7=0
INTCON2.6=0
INTCON2.4=0
INTCON2.5=0
INTCON3.7=0
INTCON3.6=1
INTCON3.4=1
INTCON3.3=1


find:
HIGH PORTC.1
PAUSE 100
LOW PORTC.1
PAUSE 100
goto find



		TRISC = %11011111		'set PORTC I/O
		SSPCON1 = %00000101		'configure SPI slave, no SS
		
		CKP = 0					'clock idle low
		CKE = 0					'transmit on idle to active transition
		SSPIF = 0				'clear SPI interrupt
		SMP = 0					'sample in middle of data

        ADCON1 = $00			'PORTA.0 analog, rest PORTA and PORTE pins to digital

loop:	
DISABLE
toggle intcon2.6
intcon.1=0
if portB.0=0 then HSEROUT["INT1 CONNECTED ",13,10]
if portB.0=1 then HSEROUT["INT1 REMOVED ",13,10]
        hserout["hello",13,10]
        gosub letclear
        SSPEN = 0				'disable/enable SSP to reset port
		hserout["hello1",13,10]
        SSPEN = 1
        'hserout["hello2",13,10]
		hserout["ok",13,10]
        GoSub letclear			'wait for byte received
		IF (SSPBUF <> "?") Then loop	'wait for ? to start conversion
		hserout["? received",13,10]
        GoSub getdata			'send "!" and string of data
		
        hserout[str dataout\5,13,10]
        hserout[str dataout2\5,13,10]
        hserout[str dataout3\5,13,10]	
		b=0
        c=0
        
        for addr=0 to 5
		e_byteout=dataout[addr]
        hserout[E_byteout,13,10]
        gosub EWrite
        next 
        
        for addr=6 to 11
		e_byteout=dataout2[b]
        b=b+1
        hserout[E_byteout,13,10]
        gosub EWrite
        next
        
        for addr=12 to 17
		e_byteout=dataout3[c]
        c=c+1
        hserout[E_byteout,13,10]
        gosub EWrite
        next
        
        pause 1000
        
        for addr=0 to 17
		a[addr]=E_bytein
        gosub ERead
        next 
        
        hserout[str a\18,13,10]
        hserout["read done",13,10]
        
        resume
        enable
        GoTo loop				'do it forever
		
getdata:
		GoSub letclear			'wait until buffer ready
		SSPBUF = "!"			'send reply
        gosub letclear
        SSPBUF = 0
		
        For i = 0 to 4			'loop for 6 array locations
		gosub letclear    		'wait until buffer ready
        dataout[i]=SSPBUF	    'send array variable
		Next i					'next location
		
        For i = 0 to 4			'loop for 6 array locations
		gosub letclear    		'wait until buffer read
        dataout2[i]=SSPBUF	    'send array variable
        Next i
        
        For i = 0 to 4			'loop for 6 array locations
		gosub letclear    		'wait until buffer read
        dataout3[i]=SSPBUF	'send array variable
        Next i
        	
        Return

letclear:
		hserout["letclear entered",13,10]
        IF SSPIF = 0 Then letclear	'wait for interrupt flag
		pauseus 25
        hserout["sspif",13,10]
        SSPIF = 0				'reset flag
		hserout["return",13,10]
        Return
		
EWrite:
        I2CWRITE SDA,SCL,%10100000,Addr,[E_ByteOut]  ' Write out the byte
        Pause 10                		' Delay 10ms after each write
        Return
	
	
ERead:
        I2CREAD SDA,SCL,%10100000,Addr,[E_ByteIn]   ' Read in the byte
        Return

myint2:
hserout["int 2 is not defined",13,10]
goto find
        
myint3:
hserout["int 3 is not defined",13,10]
goto find

decide:
disable
if intcon.1=1 then loop
if intcon3.0=1 then myint2
if intcon3.1=1 then myint3

One very important thing that i want to tell you in the slave program is this, that if you see the loop label in this program, the control successfuly displays "INT1 connected" then "hello", then "hello1", then "hello2", then "ok" but then when it comes to GOSUB letclear statement, it doesnt executes it at all. and nothing happens then. PLease see what is the problem,