;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Sensirion SHT11 sensor interface                                  ;;
;;                                                                   ;;
;; Copyleft  (L) P Pemberton                                         ;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

;; PIC setup and toplevel includes
	LIST	R=DEC
	INCLUDE	sxdefs.inc
	INCLUDE	sxregs.inc
	EXPAND				; Expand must be ON for ICD

#DEFINE	BANK0	BCF	STATUS,	PA0
#DEFINE	BANK1	BSF	STATUS,	PA0

; SX18AB
DEVICE	EQU	PINS18+OSC4MHZ+PAGES2+BANKS2
RAMBase	EQU	07h		;Start of RAM

SEROUT	MACRO	__byte
	MOVLW	__byte
;	CALL	SER_SEND
	ENDM

CHKWZ	MACRO	__outz, __outnz
	IORLW	.0
	MOVLW	__outz
	BTFSS	STATUS,		Z
	MOVLW	__outnz
;	CALL	SER_SEND
	ENDM

; Pindefs
#DEFINE	SHT_SDA	PORTB,	7
#DEFINE	SHT_SCL	PORTB,	6

; Variables
	CBLOCK	RAMBase
		TEMPERATURE:2
		HUMIDITY:2
		CHKSUM
		CHAHI, CHALO
	ENDC

; Reset vector
	ORG	0
	GOTO	START
; Interrupt vector
	ORG	4
	GOTO	START

; Start of code
	ORG	5

START:
;	CALL	SER_SETUP		; Set up the serial port

	CALL	SHT_BUSINIT		; Init the SHT bus
	MOVLW	.5			; Read Humidity
	CALL	SHT_SEND
	CALL	SHT_WAITACK		; Wait for an ACK
	CHKWZ	"A","!"

	CALL	SHT_WAIT		; Wait for the data
	CHKWZ	"W","!"

	CALL	SHT_RECEIVE		; Get byte 1
	MOVWF	HUMIDITY+0		; Store it
	CALL	SHT_ACK			; Wait for an ACK

	CALL	SHT_RECEIVE		; Get byte 2
	MOVWF	HUMIDITY+1		; Store it
	CALL	SHT_ACK			; Wait for an ACK

	CALL	SHT_RECEIVE
	MOVWF	CHKSUM
	CALL	SHT_NACK

	MOVF	HUMIDITY+0,	W	; Send humidity to host
	CALL	HEXOUT
	MOVF	HUMIDITY+1,	W
	CALL	HEXOUT
	MOVF	CHKSUM,		W
	CALL	HEXOUT

	SEROUT	" "

	GOTO	$			; Crash!

;; Subroutines

HEXOUT:
	MOVWF	CHALO
	SWAPF	CHALO,		W
	ANDLW	0x0F
	MOVWF	CHAHI
	MOVLW	0x0F
	ANDWF	CHALO

	MOVF	CHAHI,		W
	CALL	HEXTAB
;	CALL	SER_SEND

	MOVF	CHALO,		W
	CALL	HEXTAB
;	CALL	SER_SEND
	RETURN

HEXTAB:
	ADDWF	PC,	F
	DT "0123456789ABCDEF"

;; Final post-code includes
#DEFINE	SER_BAUD .19200

	INCLUDE	"sht11.inc"
	
	END