' Name        : SPISLAVE.pbp
' Compiler    : PICBASIC PRO Compiler 2.6
' Assembler   : PM or MPASM
' Target PIC  : 40-pin 16F or 18F
' Hardware    : Lab-X1, Lab-X2 or similar
' Oscillator  : 4MHz internal or external
' Keywords    : ADCIN
' Description : PicBasic Pro program SPI slave program (see spimast.pbp for connections)
' Common ground is required.
'

' Allocate RAM
dataout VAR BYTE[8]   ' Data out array
SSPEN   VAR SSPCON.5  ' SSP Enable bit
CKP     VAR SSPCON.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
i       VAR BYTE      ' loop counter
a       VAR BYTE[6]   ' Holds 6 characters of data

   TRISC = %11011111  ' set PORTC I/O
   SSPCON = %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 = $0e       ' PORTA.0 analog, rest PORTA and PORTE pins to digital

   dataout[0] = "A"   ' Preset output data to "ADC= "
   dataout[1] = "D"
   dataout[2] = "C"
   dataout[3] = "="
   dataout[4] = " "

mainloop:
   SSPEN = 0          ' disable/enable SSP to reset port
   SSPEN = 1
   GoSub letclear     ' wait for byte received
   IF (SSPBUF <> "?") Then mainloop ' wait for ? to start conversion

   ADCIN 0, dataout[5]' Read ADC channel 0, store in 6th position of string
   GoSub senddata     ' send "!" and string of data
   GoTo mainloop      ' do it forever
                
senddata:
   GoSub letclear     ' wait until buffer ready
   SSPBUF = "!"       ' send reply

   For i = 0 to 5     ' loop for 6 array locations
       GoSub letclear ' wait until buffer ready
       SSPBUF = dataout[i] ' send array variable
   Next i             ' next location
   Return
                
letclear:
   IF SSPIF = 0 Then letclear ' wait for interrupt flag
   SSPIF = 0                  ' reset flag
   Return

   End