;=============================================================================
;
;   File i2c.asm
;
;   I2C Interface to HMC5883L and MMA8452Q
;
;   HMC5883L's read address (8-Bit):    0x3D
;   HMC5883L's write address (8-Bit):   0x3C
;
;   MMA8452Q's read address (8-Bit):    0x39
;   MMA8452Q's write address (8-Bit):   0x38
;
;   LSM303D's read address (8-Bit):    0x3D
;   LSM303D's write address (8-Bit):   0x3C
;
;   Copyright (c) 2012, JD Gascuel, HeinrichsWeikamp, all right reserved.
;=============================================================================
; HISTORY
;  2012-08-22 : [mH] Creation


#include "hwos.inc"                ; Mandatory header
#include "wait.inc"
#include "math.inc"

i2c    CODE

WaitMSSP:
	decfsz		i2c_temp,F          ; check for timeout during I2C action
	bra			WaitMSSP2
	bra			I2CFail             ; timeout occured
WaitMSSP2:
	btfss		PIR1,SSPIF
	bra			WaitMSSP
	clrf		i2c_temp
	bcf			PIR1,SSPIF
	nop
	return

I2C_WaitforACK:
	btfss		SSPCON2,ACKSTAT     ; checks for ACK bit from slave
    return
I2CFail:
	rcall		I2CReset            ; I2C Reset
	bcf			PIR1,SSPIF
	clrf		i2c_temp
	return

I2CReset:                           ; Something went wrong (Slave holds SDA low?)
	clrf		SSP1CON1            ; wake-up slave and reset entire module
	clrf		SSP1CON2
	clrf		SSP1STAT
	bcf			TRISC,3             ; SCL OUTPUT
	bsf			TRISC,4             ; SDA Input
	bcf			PORTC,3
	movlw		d'9'
	movwf		i2c_temp            ; clock-out 9 clock cycles manually
I2CReset_1:
	bsf			PORTC,3             ; SCL=1
	nop
	nop
	nop
	nop
	btfsc		PORTC,4             ; SDA=1?
	bra			I2CReset_2          ; =1, SDA has been released from slave
	bcf			PORTC,3             ; SCL=0
	nop
	nop
	bcf			PORTC,3
	nop
	nop
	decfsz		i2c_temp,F
	bra         I2CReset_1          ; check for nine clock cycles
I2CReset_2:
	bsf			TRISC,3             ; SCL Input
	clrf		SSP1CON1            ; setup I²C Mode
	WAITMS		d'10'               ; Reset-Timeout for I2C devices
	movlw		b'00000000'         ; with slew rate control
	movwf		SSPSTAT
	movlw		b'00101000'
	movwf		SSP1CON1
	movlw		b'00000000'
	movwf		SSP1CON2
    movlw       0x27
	movwf		SSP1ADD
	return

I2C_TX:
	movwf		SSP1BUF
	rcall		WaitMSSP
	bra 		I2C_WaitforACK      ; Returns...

I2C_TwoBytesRX_div16:       ; Get two bytes and devide lo:hi/16 (signed)
    rcall       I2C_OneByteRX       ; Get one byte
	movff		SSP1BUF,hi          ; Data Byte
    rcall       I2C_OneByteRX       ; Get one byte
	movff		SSP1BUF,lo          ; Data Byte
I2C_TwoBytesRX_div16_2:     ; devide lo:hi/16 (signed) only
    bcf			STATUS,C
    btfsc       hi,7        ; Copy sign bit to carry
    bsf         STATUS,C
    rrcf		hi          ; /2
    rrcf		lo
I2C_TwoBytesRX_div8_2:     ; devide lo:hi/8 (signed) only
    bcf			STATUS,C
    btfsc       hi,7        ; Copy sign bit to carry
    bsf         STATUS,C
    rrcf		hi          ; /4
    rrcf		lo
    bcf			STATUS,C
    btfsc       hi,7        ; Copy sign bit to carry
    bsf         STATUS,C
    rrcf		hi          ; /8
	rrcf		lo
    bcf			STATUS,C
    btfsc       hi,7        ; Copy sign bit to carry
    bsf         STATUS,C
    rrcf		hi          ; /16
	rrcf		lo
    return

    global  I2C_RX_accelerometer
I2C_RX_accelerometer:
    btfsc   compass_type	    ; compass1?
    bra	    I2C_RX_accelerometer_compass1    ; yes
;I2C_RX_accelerometer_compass0:
    bsf			SSP1CON2,SEN		; Start condition
    rcall		WaitMSSP
    movlw		0x38                ; address
    rcall       I2C_TX
    movlw		0x00
    rcall       I2C_TX
    bsf			SSP1CON2,RSEN		; Repeated start condition (!)
    rcall		WaitMSSP
    movlw		0x39                ; address
    rcall       I2C_TX

    rcall       I2C_OneByteRX       ; Get Status Byte
    movf        SSP1BUF,W

    ; Non-flipped screen:
    ; Chip orientation on the PCB requires
    ; Original = Corrected
    ; x = -x
    ; y = -y
    ; z = -z

    ; Flipped screen:
    ; Chip orientation on the PCB requires
    ; Original = Corrected
    ; x = x
    ; y = y
    ; z = -z

    rcall       I2C_TwoBytesRX_div16 ; Get two bytes and devide /16 (signed)
    btfsc       flip_screen             ; 180° rotation ?
    bra         I2C_RX_accelerometer2   ; Yes
    comf        hi                    ; 16bit sign change.
    negf        lo
    btfsc       STATUS,C            ; Carry to propagate ?
    incf        hi,F                ; YES: do it.
I2C_RX_accelerometer2:
    movff       lo,accel_DX+0
    movff       hi,accel_DX+1       ; Copy result

    rcall       I2C_TwoBytesRX_div16 ; Get two bytes and devide /16 (signed)
    btfsc       flip_screen             ; 180° rotation ?
    bra         I2C_RX_accelerometer3   ; Yes
    comf        hi                    ; 16bit sign change.
    negf        lo
    btfsc       STATUS,C            ; Carry to propagate ?
    incf        hi,F                ; YES: do it.
I2C_RX_accelerometer3:
    movff       lo,accel_DY+0
    movff       hi,accel_DY+1       ; Copy result

    rcall       I2C_OneByteRX       ; Get one byte
	movff		SSP1BUF,hi          ; Data Byte
	bsf			SSP1CON2, RCEN      ; Enable recieve mode
    rcall		WaitMSSP
; According to datasheet there should be no Master Acknowlegde for the last Byte (accel_DZ+0)...
	movff		SSP1BUF,lo          ; Data Byte

    rcall       I2C_TwoBytesRX_div16_2; devide lo:hi/16 (signed) only
    comf        hi                    ; 16bit sign change.
    negf        lo
    btfsc       STATUS,C            ; Carry to propagate ?
    incf        hi,F                ; YES: do it.
    movff       lo,accel_DZ+0
    movff       hi,accel_DZ+1       ; Copy result

	bsf			SSP1CON2,PEN		; Stop condition
	rcall		WaitMSSP
    return

I2C_RX_accelerometer_compass1:
    bsf		SSP1CON2,SEN		; Start condition
    rcall	WaitMSSP
    movlw	0x3C                ; address
    rcall       I2C_TX
    movlw	b'10101000'	    ; 0x28 with auto-increment (MSB=1)
    rcall       I2C_TX
    bsf		SSP1CON2,RSEN	    ; Repeated start condition (!)
    rcall	WaitMSSP
    movlw	0x3D                ; address
    rcall       I2C_TX
    
    ; Non-flipped screen:
    ; Chip orientation on the PCB requires
    ; Original = Corrected
    ; x = -x
    ; y = -y
    ; z = -z

    ; Flipped screen:
    ; Chip orientation on the PCB requires
    ; Original = Corrected
    ; x = x
    ; y = y
    ; z = -z
    
    ; Dump the accelerator data
    rcall       I2C_OneByteRX       
    movff	SSP1BUF,lo  ;accel_DX+0
    rcall       I2C_OneByteRX       
    movff	SSP1BUF,hi  ;accel_DX+1
    rcall       I2C_TwoBytesRX_div16_2; devide lo:hi/16 (signed) only
    btfsc       flip_screen             ; 180° rotation ?
    bra         I2C_RX_accelerometer2_c1   ; Yes
    comf        hi                    ; 16bit sign change.
    negf        lo
    btfsc       STATUS,C            ; Carry to propagate ?
    incf        hi,F                ; YES: do it.
I2C_RX_accelerometer2_c1:
    movff       lo,accel_DX+0
    movff       hi,accel_DX+1       ; Copy result
    
    rcall       I2C_OneByteRX       
    movff	SSP1BUF,lo  ;accel_DY+0
    rcall       I2C_OneByteRX       
    movff	SSP1BUF,hi  ;accel_DY+1
    
    rcall       I2C_TwoBytesRX_div16_2; devide lo:hi/16 (signed) only
    btfsc       flip_screen             ; 180° rotation ?
    bra         I2C_RX_accelerometer3_c1   ; Yes
    comf        hi                    ; 16bit sign change.
    negf        lo
    btfsc       STATUS,C            ; Carry to propagate ?
    incf        hi,F                ; YES: do it.
I2C_RX_accelerometer3_c1:
    movff       lo,accel_DY+0
    movff       hi,accel_DY+1       ; Copy result

    rcall       I2C_OneByteRX     
    movff	SSP1BUF,lo  ;accel_DZ+0
    bsf		SSP1CON2, RCEN      ; Enable recieve mode
    rcall	WaitMSSP
; According to datasheet there should be no Master Acknowlegde for the last Byte (accel_DZ+1)...
    movff	SSP1BUF,hi  ;accel_DZ+1
    bsf		SSP1CON2,PEN		; Stop condition
    rcall	WaitMSSP
    rcall       I2C_TwoBytesRX_div16_2; devide lo:hi/16 (signed) only
    comf        hi                    ; 16bit sign change for Z
    negf        lo
    btfsc       STATUS,C            ; Carry to propagate ?
    incf        hi,F                ; YES: do it.
    movff       lo,accel_DZ+0
    movff       hi,accel_DZ+1       ; Copy result
    return
    
I2C_OneByteRX:
    bsf		SSP1CON2, RCEN      ; Enable recieve mode
    rcall	WaitMSSP
    bsf		SSP1CON2,ACKEN	    ; Master acknowlegde
    bra		WaitMSSP	    ; And return!

    global  I2C_RX_compass
I2C_RX_compass:
    btfsc   compass_type	    ; compass1?
    bra	    I2C_RX_compass1    ; yes
;I2C_RX_compass0:
    bsf		SSP1CON2,SEN		; Start condition
    rcall	WaitMSSP
    movlw	0x3C                ; address
    rcall       I2C_TX
    movlw	0x03
    rcall       I2C_TX
    bsf		SSP1CON2,PEN		; Stop condition
    rcall	WaitMSSP

    bcf		PIR1,SSPIF
    bsf		SSP1CON2,SEN		; Start condition
    rcall	WaitMSSP
    movlw	0x3D                ; address
    rcall       I2C_TX

    ; Compass IC sends data in following order:
    ; x MSB
    ; x LSB
    ; z MSB
    ; z LSB
    ; y MSB
    ; y LSB

    ; Non-flipped screen
    ; Chip orientation on the PCB requires
    ; Original = Corrected
    ; x = -y
    ; z = z
    ; y = x

    ; Flipped screen
    ; Chip orientation on the PCB requires
    ; Original = Corrected
    ; x = y
    ; z = z
    ; y = -x

    rcall       I2C_OneByteRX       ; Get one byte
	movff		SSP1BUF,compass_DY+1; Data Byte
    rcall       I2C_OneByteRX       ; Get one byte
	movff		SSP1BUF,compass_DY+0; Data Byte
    btfsc       flip_screen         ; 180° rotation ?
    bra         I2C_RX_compass2     ; Yes
    banksel compass_DY
    comf        compass_DY+1        ; 16bit sign change.
    negf        compass_DY+0
    btfsc       STATUS,C            ; Carry to propagate ?
    incf        compass_DY+1,F      ; YES: do it.
I2C_RX_compass2:
    banksel common
    rcall       I2C_OneByteRX       ; Get one byte
    movff	SSP1BUF,compass_DZ+1; Data Byte
    rcall       I2C_OneByteRX       ; Get one byte
    movff	SSP1BUF,compass_DZ+0; Data Byte
    rcall       I2C_OneByteRX       ; Get one byte
    movff	SSP1BUF,compass_DX+1; Data Byte
    bsf		SSP1CON2, RCEN      ; Enable recieve mode
    rcall	WaitMSSP
    movff	SSP1BUF,compass_DX+0; Data Byte
    bsf		SSP1CON2,PEN	    ; Stop condition
    rcall	WaitMSSP
    btfss       flip_screen         ; 180° rotation ?
    return                          ; No, done.
    ; Yes, flip X
    banksel compass_DX
    comf        compass_DX+1        ; 16bit sign change.
    negf        compass_DX+0
    btfsc       STATUS,C            ; Carry to propagate ?
    incf        compass_DX+1,F      ; YES: do it.
    banksel common
    return
    
I2C_RX_compass1: ; New compass
    bsf		SSP1CON2,SEN	    ; Start condition
    rcall	WaitMSSP
    movlw	0x3C                ; address
    rcall       I2C_TX
    movlw	b'10001000'	    ; 0x08 with auto-increment (MSB=1)
    rcall       I2C_TX
    bsf		SSP1CON2,RSEN	    ; Repeated start condition (!)
    rcall	WaitMSSP
    movlw	0x3D                ; address
    rcall       I2C_TX

    rcall	I2C_OneByteRX       ; Get one byte
    movff	SSP1BUF,lo	    ; Data Byte
    rcall	I2C_OneByteRX       ; Get one byte
    movff	SSP1BUF,hi	    ; Data Byte
    rcall	I2C_TwoBytesRX_div8_2
    movff	lo,compass_DX+0
    movff	hi,compass_DX+1
    btfss       flip_screen         ; 180° rotation ?
    bra		I2C_RX_compass1_1              ; Yes
    ; Yes, flip X
    banksel compass_DX
    comf        compass_DX+1        ; 16bit sign change.
    negf        compass_DX+0
    btfsc       STATUS,C            ; Carry to propagate ?
    incf        compass_DX+1,F      ; YES: do it.
    banksel common
I2C_RX_compass1_1:
    rcall	I2C_OneByteRX       ; Get one byte
    movff	SSP1BUF,lo	    ; Data Byte
    rcall	I2C_OneByteRX       ; Get one byte
    movff	SSP1BUF,hi	    ; Data Byte
    rcall	I2C_TwoBytesRX_div8_2
    movff	lo,compass_DY+0
    movff	hi,compass_DY+1
    btfss       flip_screen         ; 180° rotation ?
    bra         I2C_RX_compass1_2   ; Yes
    ; Yes, flip Y
    banksel compass_DY
    comf        compass_DY+1        ; 16bit sign change.
    negf        compass_DY+0
    btfsc       STATUS,C            ; Carry to propagate ?
    incf        compass_DY+1,F      ; YES: do it.
I2C_RX_compass1_2:
    banksel common
    rcall	I2C_OneByteRX       ; Get one byte
    movff	SSP1BUF,lo	    ; Data Byte
    bsf		SSP1CON2, RCEN      ; Enable recieve mode
    rcall	WaitMSSP
    movff	SSP1BUF,hi	    ; Data Byte
    rcall	I2C_TwoBytesRX_div8_2
    movff	lo,compass_DZ+0
    movff	hi,compass_DZ+1
    bsf		SSP1CON2,PEN	    ; Stop condition
    rcall	WaitMSSP
    return

    global  I2C_init_compass
I2C_init_compass:
    bsf     compass_enabled
    bsf	    compass_type	    ; set flag
    bsf	    SSP1CON2,SEN		; Start condition
    rcall   WaitMSSP
    movlw   0x3C                ; address
    rcall   I2C_TX
    movlw   0x0F
    rcall   I2C_TX
    bsf	    SSP1CON2,PEN		; Stop condition
    rcall   WaitMSSP
    bcf	    PIR1,SSPIF
    bsf	    SSP1CON2,SEN		; Start condition
    rcall   WaitMSSP
    movlw   0x3D                ; address
    rcall   I2C_TX
    rcall   I2C_OneByteRX       ; Get one byte
    movlw   0x49		; 0x49 = Compass1
    cpfseq  SSP1BUF
    bcf	    compass_type	    ; clear flag
    bsf	    SSP1CON2,PEN		; Stop condition
    rcall   WaitMSSP

    btfsc   compass_type	    ; compass1?
    bra	    I2C_init_compass1	    ; yes
; init compass0
    bsf		SSP1CON2,SEN		; Start condition
    rcall	WaitMSSP
    movlw	0x3C                ; address
    rcall       I2C_TX
    movlw	0x00
    rcall       I2C_TX
;	movlw	b'01101001'        ; ConfigA:  3Hz, 8 Samples averaged, Test Mode (Positive Bias)
    movlw	b'01101000'        ; ConfigA:  3Hz, 8 Samples averaged
    rcall       I2C_TX
    bra         I2C_init_compass_common

    global  I2C_init_compass_fast
I2C_init_compass_fast:
    btfsc   compass_type	    ; compass1?
    bra	    I2C_init_compass_fast1  ; yes
;I2C_init_compass_fast0:
    bsf		SSP1CON2,SEN		; Start condition
    rcall	WaitMSSP
    movlw	0x3C                ; address
    rcall       I2C_TX
    movlw	0x00
    rcall       I2C_TX
    movlw	b'00111000'        ; ConfigA: 75Hz, 2 Samples averaged
;    movlw	b'00111001'        ; ConfigA: 75Hz, 2 Samples averaged, Test Mode (Positive Bias)
    rcall       I2C_TX
I2C_init_compass_common:
    movff       opt_compass_gain,i2c_temp    ; 0-7 (230LSB/Gauss to 1370LSB/Gauss)
    swapf       i2c_temp,F
    comf        i2c_temp,F
    bcf         STATUS,C
    rlcf        i2c_temp
    movf        i2c_temp,W
    clrf        i2c_temp
    rcall       I2C_TX
    movlw	b'00000000'        ; Continous Mode
    rcall       I2C_TX
    bsf	SSP1CON2,PEN		; Stop condition
    rcall	WaitMSSP
    return

I2C_init_compass1:
    bsf		SSP1CON2,SEN	; Start condition
    rcall	WaitMSSP
    movlw	0x3C            ; address
    rcall       I2C_TX
    movlw	0x9F		; 1F with auto-increment (MSB=1)
    rcall       I2C_TX
    movlw	b'00000000'	; CTRL0
    rcall       I2C_TX
    movlw	b'00101111'	; CTRL1 (6,25Hz, BDU=0, x,y,z = ON)
    rcall       I2C_TX
    movlw	b'11000000'	; CTRL2 (50Hz, +/-2g, 
    rcall       I2C_TX
    movlw	b'00000000'	; CTRL3
    rcall       I2C_TX
    movlw	b'00000000'	; CTRL4
    rcall       I2C_TX
    movlw	b'01100100'	; CTRL5 HIGH res, 6,25Hz
    rcall       I2C_TX
init_compass1_common:
    movlw	b'01100000'	; CTRL6 Full scale (+/-12 Gauss -> 2730LSB/Gauss)
    ;movlw	b'00000000'	; CTRL6 (+/-2 Gauss)
    ;movlw	b'00100000'	; CTRL6 (+/-4 Gauss)
    rcall       I2C_TX
    movlw	b'00000000'	; CTRL7 Continuous Mode
    rcall       I2C_TX
    bsf		SSP1CON2,PEN		; Stop condition
    rcall	WaitMSSP
    return
    
I2C_init_compass_fast1:
    bsf		SSP1CON2,SEN		; Start condition
    rcall	WaitMSSP
    movlw	0x3C            ; address
    rcall       I2C_TX
    movlw	0x9F		; 1F with auto-increment (MSB=1)
    rcall       I2C_TX
    movlw	b'00000000'	; CTRL0
    rcall       I2C_TX
    movlw	b'01101111'	; CTRL1 (100Hz, BDU=0, x,y,z = ON)
    rcall       I2C_TX
    movlw	b'11000000'	; CTRL2 (50Hz, +/-2g, 
    rcall       I2C_TX
    movlw	b'00000000'	; CTRL3
    rcall       I2C_TX
    movlw	b'00000000'	; CTRL4
    rcall       I2C_TX
    movlw	b'01110100'	; CTRL5 HIGH res, 100Hz
    rcall       I2C_TX
    bra		init_compass1_common
    
    global  I2C_sleep_compass
I2C_sleep_compass:
    bcf         compass_enabled
    
    btfsc   compass_type	    ; compass1?
    bra	    I2C_sleep_compass1	    ; yes
;I2C_sleep_compass0:
    bsf		SSP1CON2,SEN		; Start condition
    rcall	WaitMSSP
    movlw	0x3C                ; address
    rcall       I2C_TX
    movlw	0x00
    rcall       I2C_TX
    movlw	b'01101000'        ; ConfigA
    rcall       I2C_TX
    movlw	b'00100000'        ; ConfigB
    rcall       I2C_TX
    movlw	b'00000010'        ; Idle Mode
    rcall       I2C_TX
    bsf		SSP1CON2,PEN		; Stop condition
    rcall	WaitMSSP
    return

I2C_sleep_compass1:
    bsf		SSP1CON2,SEN	    ; Start condition
    rcall	WaitMSSP
    movlw	0x3C                ; address
    rcall       I2C_TX
    movlw	0x20		    ; CTRL_REG1
    rcall       I2C_TX
    movlw	b'00000000'         ; data for CTRL_REG1: acceleration sensor Power-down mode
    rcall       I2C_TX
    bsf		SSP1CON2,PEN	    ; Stop condition
    rcall	WaitMSSP
    bsf		SSP1CON2,SEN	    ; Start condition
    rcall	WaitMSSP
    movlw	0x3C                ; address
    rcall       I2C_TX
    movlw	0x26		    ; CTRL_REG7
    rcall       I2C_TX
    movlw	b'00000010'         ; data for CTRL_REG7: magnetic sensor Power-down mode
    rcall       I2C_TX
    bsf		SSP1CON2,PEN	    ; Stop condition
    rcall	WaitMSSP
    return
    

   global  I2C_init_accelerometer
I2C_init_accelerometer:
    btfsc   compass_type	    ; compass1?
    return			    ; yes, ignore

    rcall       I2C_sleep_accelerometer ; Regs can only be changed in St.By mode

	bsf			SSP1CON2,SEN		; Start condition
	rcall		WaitMSSP
	movlw		0x38                ; address
    rcall       I2C_TX
	movlw		0x0E                ; XYZ_DATA_CFG
    rcall       I2C_TX
	movlw		b'00000000'         ; High pass Filter=0 , +/- 2g range
    rcall       I2C_TX
	bsf			SSP1CON2,PEN		; Stop condition
	rcall		WaitMSSP


	bsf			SSP1CON2,SEN		; Start condition
	rcall		WaitMSSP
	movlw		0x38                ; address
    rcall       I2C_TX
	movlw		0x2A                ; CTRL_REG1
    rcall       I2C_TX
;	movlw		b'00110000'         ; CTRL_REG1: 160ms data rate, St.By Mode
	movlw		b'00110100'         ; CTRL_REG1: 160ms data rate, St.By Mode, reduced noise mode
    rcall       I2C_TX
	movlw		b'00000010'         ; CTRL_REG2: High Res in Active mode
    rcall       I2C_TX
	bsf			SSP1CON2,PEN		; Stop condition
	rcall		WaitMSSP

	bsf			SSP1CON2,SEN		; Start condition
	rcall		WaitMSSP
	movlw		0x38                ; address
    rcall       I2C_TX
	movlw		0x2A                ; CTRL_REG1
    rcall       I2C_TX
;	movlw		b'00110001'         ; CTRL_REG1: 160ms data rate, Active Mode
	movlw		b'00110101'         ; CTRL_REG1: 160ms data rate, St.By Mode, reduced noise mode, Active Mode
    rcall       I2C_TX
	bsf			SSP1CON2,PEN		; Stop condition
	rcall		WaitMSSP

    return

    global  I2C_sleep_accelerometer
I2C_sleep_accelerometer:
    btfsc   compass_type	    ; compass1?
    return			    ; yes, ignore

	bsf			SSP1CON2,SEN		; Start condition
	rcall		WaitMSSP
	movlw		0x38                ; address
    rcall       I2C_TX
	movlw		0x2A                ; CTRL_REG1
    rcall       I2C_TX
	movlw		b'00000000'         ; St. By Mode
    rcall       I2C_TX
	bsf			SSP1CON2,PEN		; Stop condition
	rcall		WaitMSSP
    return

    global  lt2942_init
lt2942_init:                    ; Setup Control register B
	clrf	i2c_temp
	movlw	0x01                ; Point to control reg B
	rcall	I2C_TX_GAUGE
	movlw   b'11111000'         ; Automatic conversion every two seconds
	movff	WREG, SSP1BUF       ; Data Byte
	rcall	WaitMSSP
	rcall	I2C_WaitforACK
	bsf		SSP1CON2,PEN		; Stop condition
	bra	WaitMSSP ;   (And return)

	global	lt2942_get_status
lt2942_get_status:          ; Read status register
    bcf     battery_gauge_available     ; Clear flag
	clrf	i2c_temp
	movlw	0x00            ; Point to Status reg
	rcall	I2C_TX_GAUGE
	rcall	I2C_RX_GAUGE
	movff	SSP1BUF,WREG
        btfss   WREG,7          ; 2942 found?
        bsf     battery_gauge_available     ; Yes, set flag
	bsf	SSP1CON2,PEN	; Stop condition
	bra	WaitMSSP ;   (And return)


	global	lt2942_get_voltage
lt2942_get_voltage:		; Read battery voltage registers
	clrf	i2c_temp
	movlw	0x08        ; Point to voltage registers
	rcall	I2C_TX_GAUGE
	rcall	I2C_RX_GAUGE
	bsf		SSP1CON2,ACKEN		; Master acknowlegde
	rcall	WaitMSSP
	movff	SSP1BUF,xA+1
	bsf		SSP1CON2, RCEN		; Enable recieve mode
	rcall	WaitMSSP
	movff	SSP1BUF,xA+0
	bsf		SSP1CON2,PEN		; Stop condition
	rcall	WaitMSSP

;	banksel	common
    ; xA:2 loaded with raw values
    movlw   LOW     .6000
    movwf   xB+0
    movlw   HIGH    .6000
    movwf   xB+1
    call    mult16x16		;xA*xB=xC

    ; devide xC (32bit)/65535 for result in mV (16bit)
    movlw   .16
    movwf   i2c_temp
lt2942_get_voltage2:
    bcf     STATUS,C
    rrcf    xC+3,F
    rrcf    xC+2,F
    rrcf    xC+1,F
    rrcf    xC+0,F
    decfsz  i2c_temp,F
    bra     lt2942_get_voltage2

    ; Update battery voltage in mV
    movff   xC+1,batt_voltage+1
    movff   xC+0,batt_voltage+0
    
    tstfsz  batt_voltage+1  ; <256mV?
    return		    ; No, done.

    rcall   lt2942_init
    return

;	global	lt2942_get_temperature
;lt2942_get_temperature:		; Read temperature registers
;	clrf	i2c_temp
;	movlw	0x0C            ; Point to temperature registers
;	call	I2C_TX_GAUGE
;	call	I2C_RX
;	bsf		SSP1CON2,ACKEN	; Master acknowlegde
;	rcall	WaitMSSP
;	movff	SSP1BUF,xA+1
;	bsf		SSP1CON2, RCEN	; Enable recieve mode
;	rcall	WaitMSSP
;	movff	SSP1BUF,xA+0
;	bsf		SSP1CON2,PEN	; Stop condition
;	rcall	WaitMSSP
;
;;	banksel	common
;    ; xA:2 loaded with raw values
;    movlw   LOW     .6000
;    movwf   xB+0
;    movlw   HIGH    .6000
;    movwf   xB+1
;    call    mult16x16		;xA*xB=xC
;
;    ; devide xC (32bit)/65535 for result in 0.1K (16bit)
;    movlw   .16
;    movwf   i2c_temp
;lt2942_get_temperature2:
;    bcf     STATUS,C
;    rrcf    xC+3,F
;    rrcf    xC+2,F
;    rrcf    xC+1,F
;    rrcf    xC+0,F
;    decfsz  i2c_temp,F
;    bra     lt2942_get_temperature2
;
;    movff   xC+1,sub_a+1
;    movff   xC+0,sub_a+0
;    movlw   LOW     .2731       ; Kelvin to Celcius offset
;    movwf   sub_b+0
;    movlw   HIGH    .2731       ; Kelvin to Celcius offset
;    movwf   sub_b+1
;    call    subU16  ;  sub_c = sub_a - sub_b (with UNSIGNED values)
;
;    ; Update batttery_temperature in 0.1°C
;    movff   sub_c+1,battery_temperature+1
;    movff   sub_c+0,battery_temperature+0
;	return

	global	lt2942_get_accumulated_charge
lt2942_get_accumulated_charge:	; Read accumulated charge and compute percent
	clrf	i2c_temp
	movlw	0x00                ; Point to status register
	rcall	I2C_TX_GAUGE
	rcall	I2C_RX_GAUGE
	bsf	SSP1CON2,ACKEN      ; Master acknowlegde
	rcall	WaitMSSP
	movff	SSP1BUF,gauge_status_byte

	bsf	SSP1CON2, RCEN      ; Enable recieve mode
	rcall	WaitMSSP	    ; Dummy read (Control byte)
	movf	SSP1BUF,W
	bsf	SSP1CON2,ACKEN      ; Master acknowlegde
	rcall	WaitMSSP
	
	bsf	SSP1CON2, RCEN      ; Enable recieve mode
	rcall	WaitMSSP
	movff	SSP1BUF,sub_a+1
	bsf	SSP1CON2,ACKEN      ; Master acknowlegde
	rcall	WaitMSSP
	
	bsf	SSP1CON2, RCEN      ; Enable recieve mode
	rcall	WaitMSSP
	movff	SSP1BUF,sub_a+0
	bsf	SSP1CON2,PEN        ; Stop condition
	rcall	WaitMSSP
	
	movff	gauge_status_byte,sub_b+0   ; copy into bank common
	btfsc	sub_b+0,0		    ; =1: UVLO Event
	rcall	lt2942_init

	movff	sub_a+1,battery_acumulated_charge+1 ; Save raw value
	movff	sub_a+0,battery_acumulated_charge+0 ; Save raw value
	
    ; Compute batt_percent
    ; (charge-battery_offset)/365
    movff   battery_offset+0,sub_b+0
    movff   battery_offset+1,sub_b+1
    call    subU16          ;  sub_c = sub_a - sub_b (with signed values)

    clrf    batt_percent   ; Set to zero
    btfsc   neg_flag                ; result negative?
    bra	    lt2942_set_to_zero_percent	; Yes, keep LT2942 at zero percent and return

    ; > Zero, set batt_percent properly
    movff   sub_c+0,xA+0
    movff   sub_c+1,xA+1
    movff   battery_capacity+0,xB+0
    movff   battery_capacity+1,xB+1
    call    div16x16						;xA/xB=xC with xA+0 as remainder, uses divB as temp variable
    movff   xC+0,batt_percent
    return

lt2942_set_to_zero_percent:
	clrf	i2c_temp
	movlw	0x02                ; Point to accumulated charge registers
	rcall	I2C_TX_GAUGE
	movff	battery_offset+1,SSP1BUF
	rcall	WaitMSSP
	rcall	I2C_WaitforACK
	movff	battery_offset+0,SSP1BUF
	rcall	WaitMSSP
	rcall	I2C_WaitforACK
	bsf	SSP1CON2,PEN		; Stop condition
	bra	WaitMSSP; (and return)

	global	lt2942_charge_done
lt2942_charge_done:                 ; Reset accumulating registers to 0xFFFF
	clrf	i2c_temp
	movlw	0x02                ; Point to accumulated charge registers
	rcall	I2C_TX_GAUGE
	setf	SSP1BUF       ; Data Byte
	rcall	WaitMSSP
	rcall	I2C_WaitforACK
	setf	SSP1BUF       ; Data Byte
	rcall	WaitMSSP
	rcall	I2C_WaitforACK
	bsf	SSP1CON2,PEN		; Stop condition
	bra	WaitMSSP; (and return)

I2C_TX_GAUGE:					; Sends a byte to the LT2942 Gauge IC
	movwf	i2c_temp+1   		; Data byte
	bsf	SSP1CON2,SEN		; Start condition
	rcall	WaitMSSP
	movlw	b'11001000'			; Address byte + Write bit
	movwf	SSP1BUF				; control byte
	rcall	WaitMSSP
	rcall	I2C_WaitforACK
	movff	i2c_temp+1, SSP1BUF	; Data Byte
	rcall	WaitMSSP
	bra	I2C_WaitforACK ; (and return)

I2C_RX_GAUGE:
	bsf		SSP1CON2,SEN		; Start condition
	rcall	WaitMSSP
	movlw	b'11001001'			; Address byte + Read bit
	movwf	SSP1BUF				; control byte
	rcall	WaitMSSP
	rcall	I2C_WaitforACK
	bsf	SSP1CON2, RCEN			; Enable recieve mode
	bra	WaitMSSP; (and return)
    
    END