title		"OpenTherm Gateway"
		list		p=16F88, b=8, r=dec

;Copyright (c) 2009 Schelte Bron

#define		version		"4.2"
#define		phase		"."	;a=alpha, b=beta, .=production
#define 	patch		"5"	;Comment out when not applicable
;#define 	bugfix		"1"	;Comment out when not applicable
#include	build.asm

;See the file "license.txt" for information on usage and redistribution of
;this file, and for a DISCLAIMER OF ALL WARRANTIES.

#ifndef LVP
		__config	H'2007', B'10111101110100'
#else
		__config	H'2007', B'10111111110100'
#endif
		__config	H'2008', B'11111111111111'

		errorlevel	-302

;#######################################################################
;Comparator 1 is used for requests. The input is connected to the thermostat.
;In monitor mode, the output is connected to the boiler.
;Comparator 2 is used for responses. The input is connected to the Boiler.
;In monitor mode, the output is connected to the thermostat.

;The AUSART is configured for full duplex asynchronous serial communication at
;9600 baud, 8 bits, no parity. It is used for reporting about opentherm messages
;and receiving commands.

;Analog input 0 is used to measure the voltage level on the opentherm line to
;the thermostat. This way the code can distinguish between a real opentherm
;thermostat and a simple on/off thermostat. An opentherm thermostat will keep
;the line at a few volts (low) or between 15 and 18 volts (high). An on/off
;thermostat will either short-circuit the line (0 volts) or leave the line open
;(20+ volts).

#include	"p16f88.inc"

;Define the speed of the PIC clock
#define		mhzstr	"4"

;BAUD contains the SPBRG value for 9600 baud
		constant BAUD=25

		extern	SelfProg

;Variables accessible from all RAM banks
		UDATA_SHR
loopcounter	res	1

Bank0data	UDATA	0x20
rxbuffer	res	16	;Serial receive buffer

;Variables for longer lasting storage
rxpointer	res	1
txpointer	res	1

temp		res	1

Bank1data	UDATA	0xA0

Bank1values	UDATA	0xE0

Bank2data	UDATA	0x110
Bank2values	UDATA	0x160

Bank3data	UDATA	0x190
;Use all available RAM in bank 3 for the transmit buffer
		constant TXBUFSIZE=80
txbuffer	res	TXBUFSIZE
Bank3values	UDATA	0x1E0

;I/O map
#define		MasterIn	CMCON,C1OUT
#define		SlaveIn		CMCON,C2OUT
#define		SlaveOut	PORTA,3
#define		MasterOut	PORTA,4
#define		RXD		PORTB,2
#define		TXD		PORTB,5
#define		CCP1		PORTB,0
#define		LED_A		PORTB,3
#define		LED_B		PORTB,4
#define		LED_C		PORTB,6
#define		LED_D		PORTB,7
#define		RSET		PORTB,1		;Used by self-programming

#define		SlaveMask	b'00001000'
#define		MasterMask	b'00010000'

package		macro	pkg
pkg		code
pkg
		endm

pcall		macro	rtn
		lcall	rtn
		pagesel	$
		endm

;Skip the next instruction (bit 7 of PCLATH is always 0)
skip		macro
		btfsc	PCLATH,7
		endm

;Get the output of the active comparator into the carry bit
getcompout	macro
		bsf	STATUS,RP0
		rlf	CMCON,W		;Get the output of comparator 2
		bcf	STATUS,RP0
		btfsc	Request		;A request goes through comparator 1
		addlw	b'10000000'	;Cause a carry if C1OUT is high
		endm

;The first thing to do upon a reset is to allow the firmware to be updated.
;So no matter how buggy freshly loaded firmware is, if the first two command
;have not been messed up, the device can always be recovered without the need
;for a PIC programmer. The self-programming code times out and returns after
;a second when no firmware update is performed.
;

ResetVector	code	0x0000
		lcall	SelfProg	;Always allow a firmware update on boot
		lgoto	Start		;Start the opentherm gateway program

InterruptVector	code	0x0004
		retfie			;End of interrupt routine

		package Interrupt

;########################################################################
; Main program
;########################################################################

		package Main
Break		tstf	RCREG		;Clear the RCIF interrupt flag
		bcf	STATUS,RP1
		bcf	STATUS,RP0	;bank 0
		movlw	128
		call	Pause
		pcall	SelfProg	;Jump to the self-programming code
Start		bcf	STATUS,RP1
		bcf	STATUS,RP0	;bank 0
		clrf	PORTB		;Flash the LED's on startup
		bsf	STATUS,RP0
		movlw	b'01100000'	;Internal oscillator set to 4MHz
		movwf	OSCCON		;Configure the oscillator

		;Configure I/O pins
		;Power on defaults all pins to inputs
		;Port A
		;Pins 0 and 1 are used as comparator inputs
		;Pin 2 is used as VREF (must be configured as input!)
		;Pins 3 and 4 are (comparator) ouputs
		;Pin 5 is master reset input
		;Pins 6 and 7 are GPIO
		movlw	b'11100111'
		movwf	TRISA
 
		;Port B
		;Pins 2 and 5 are used by the USART and don't need to be configured
		;Pins 3, 4, 6, and 7 are used to indicate events for debugging
#ifndef LVP
		movlw	b'00100111'
#else
		;Can't use RB3 if LVP is enabled
		movlw	b'00101111'
#endif
		movwf	TRISB

		movlw	b'11'
		movwf	PCON

		;Configure Timer 0 & Watchdog Timer
		;Bit 7 RBPU = 1 - Port B pull up disabled
		;Bit 6 INTEDG = 1 - Interrupt on rising edge
		;Bit 5 T0CS = 0 - Internal clock
		;Bit 4 T0SE = 1 - High to low transition
		;Bit 3 PSA = 0 - Prescaler assigned to Timer 0
		;Bit 2-0 PS = 5 - 1:64 Prescaler
		movlw	b'11010101'
		movwf	OPTION_REG


		;Configure comparator module
		;Bit 7 C2OUT = R/O
		;Bit 6 C1OUT = R/O
		;Bit 5 C2INV = 0 - Not inverted
		;Bit 4 C1INV = 0 - Not inverted
		;Bit 3 CIS = 0 - Irrelevant
		;Bit 2-0 = 3 - Common reference / 6 - with outputs
		movlw	b'00000011'	;Common reference mode
		movwf	CMCON

		movlw	b'00000111'	;A0 through A2 are used for analog I/O
		movwf	ANSEL

		;Configure the serial interface
		movlw	BAUD
		movwf	SPBRG
		bsf	TXSTA,BRGH	;9600 baud
		bcf	TXSTA,SYNC	;Asynchronous
		bsf	TXSTA,TXEN	;Enable transmit
		bcf	STATUS,RP0
		bsf	RCSTA,SPEN	;Enable serial port
		bsf	RCSTA,CREN	;Enable receive

		;Configure A/D converter
		movlw	b'01000001'	;A/D on, channel 0, Fosc/8
		movwf	ADCON0

		;Configure the voltage reference module
		;The reference voltage must be set to 1.3V
		;Bit 7 VREN = 1 - VREF Enabled
		;Bit 6 VROE = 1 - Output on pin RA2
		;Bit 5 VRR = 1 - Low range
		;Bit 3-0 VR = 6 - 1.25V (7 - 1.46V)
		movlw	b'11100110'
		bsf	STATUS,RP0
		movwf	CVRCON		;Set the reference voltage


		clrf	STATUS
		bcf	PIR2,CMIF	;Clear any comparator interrupt

		movlw	0x41
		movwf	TXREG
		



MainLoop	clrwdt

		; Copy CMCON bits 7 and 6 from to PORTB bits 7 and 6 (comparitor outputs to LED_C and LED_D pins)
		bsf	STATUS,RP0
		movfw	CMCON
		bcf	STATUS,RP0

		andlw	b'11000000'
		iorwf   PORTB,F
		iorlw   b'00111111'
		andwf   PORTB,F

		; Copy PORTA bits 7 and 6 to PORTA bits 4 and 3 (GPIO inputs to transmitter outputs)
		rrf     PORTA,W
		movwf   temp
		rrf 	temp,F
		rrf 	temp,W

		andlw	b'00011000'
		iorwf   PORTA,F
		iorlw   b'11100111'
		andwf   PORTA,F

		; And port B bits 4 and 3 (LED_A and LED_B)

		andlw	b'00011000'
		iorwf   PORTB,F
		iorlw   b'11100111'
		andwf   PORTB,F


		btfss	PIR1,RCIF	;Activity on the serial receiver?
		goto	MainLoop
		tstf    RCREG

		;FERR is only relevant if RCIF is set
		btfsc	RCSTA,FERR	;Check for framing error (break)
		goto 	Break
		btfss	RCSTA,OERR	;Check for overrun error
		goto 	serial_recv	
		bcf	RCSTA,CREN	;Procedure to clear an overrun error
		bsf	RCSTA,CREN	;Re-enable the serial interface
serial_recv	movfw   RCREG
		;movwf	TXREG
		xorlw	0x4
		skpnz
		goto 	Break
		goto MainLoop

Pause		clrwdt
		btfsc	PIR1,RCIF
		return
		btfss	INTCON,TMR0IF
		goto	Pause
		bcf	INTCON,TMR0IF
		addlw	-1
		skpz
		goto	Pause
		return


		end