;+===========================+
;|John Murphy                |
;|Kenneth Heck               |
;|                           |
;|CAN bus adaptor            |
;|28 November, 2001          |
;|                           |
;+===========================+



;****************************
;       TO DO
; "_" means TO DO
; "x" means done and tested (But may be breaking another section of code)
; "?" means done, but untested/ not working properly
;----------------------------
; ? Configure 2510 to send interrupt
; ? Receive multiple bytes at a time from the 2510 registers
; _ Detect mode
; ? Put in CF stub functions
;
;****************************
	list p=16f877

	; Include file, change directory if needed
	include "p16f877.inc"
	__CONFIG _CP_OFF & _WDT_OFF & _BODEN_OFF & _PWRTE_OFF & _HS_OSC & _WRT_ENABLE_OFF & _LVP_ON & _DEBUG_OFF & _CPD_OFF 

#define	debug
;#define echo

;+===========================+
;| Variables                 |
;+===========================+

;For the Interrupt Service Routines:
	W_TEMP		equ	0x71
	STATUS_TEMP	equ	0x72
	PCLATH_TEMP	equ	0x73
	FSR_TEMP	equ	0x74



;***************************************
;        DEVMODE
;Device's Mode/STATUS Byte
; Bit 0-2	MODE SELECT
; Bit 3		PC_buff overflow error
; Bit 4		CAN_buff overflow error
; Bit 5		CompactFlash full error
; Bit 6		PC_buff contains data
;***************************************
	DEVMODE		equ	0x75
	#define	PC_BUFF_OVERFLOW	DEVMODE, 3
	#define	CAN_BUFF_OVERFLOW	DEVMODE, 4
	#define	CF_INSERTED		DEVMODE, 5
	#define PC_BUFF_NOTEMPTY	DEVMODE, 6
	#define	CAN_BUFF_NOTEMPTY	DEVMODE, 7

	DEVFLAG		equ	0x76
	#define	CAN_RX0_READY		DEVFLAG, 0
	#define	CAN_RX1_READY		DEVFLAG, 1
	#define	SPI_IN_PROGRESS		DEVFLAG, 2
	#define	USART_IN_PROGRESS	DEVFLAG, 3
	#define	CF_IN_PROGRESS		DEVFLAG, 4

	

	delay 		equ	0x21
	rcv		equ	0x22
	loopctr0	equ	0x23
;Whenever we write to the 2510, we write two bytes at a time.  Load 
;them into these first, then call SPI_Write
; And yes, these are all in the same bank as SSBUF.  Makes life much easier later on.

	SPI1	equ	0x26
	SPI2	equ	0x27
	SPI3	equ	0x28
	SPIOUT	equ	0x29

	CF_DATA_HIGH	equ	0x2A
	CD_DATA_LO	equ	0x2B

	POWER_ON_MSG	equ	0x55
	INIT_MSG	equ	0x42
	
;Here are our buffers:
	CAN_buff_in	equ	0xE5
	CAN_buff_out	equ	0xE6
	CAN_buff_ctr	equ	0xE7

	PC_buff_in	equ	0x33
	PC_buff_out	equ	0x34
	PC_buff_ctr	equ	0x35
	outcounter	equ	0x36

	PC_buff		equ	0x40	;This ends at 0x50, for 16 bytes -- two CAN packets' worth
	PC_buff_end	equ	0x51
	CAN_buff	equ	0xA0	;This stretches out to 0xE0h -- 64 bytes
	CAN_buff_end	equ	0xE1


;+===========================+
;| Constants                 |
;+===========================+

#define		CAN_CS	PORTB, 2
#define		TXB0_TX	PORTB, 6
#define		TXB1_TX	PORTB, 5

;Compact Flash control lines
#define		CF_RESET	PORTA, 5	;Output
#define		CF_CD1		PORTA, 1	;Output
#define		CF_OE		PORTA, 2	;Output
#define		CF_WE		PORTA, 3	;Output
#define		CF_RDY		PORTA, 4	;Input
#define		CF_CE1		PORTA, 0	;Output


;+============================+
;    CANSTAT bits 3-1
;     Interrupt flag code
;     000 = No Interrupt
;     001 = Error Interrupt
;     010 = Wake Up Interrupt
;     011 = TXB0 Interrupt
;     100 = TXB1 Interrupt
;     101 = TXB2 Interrupt
;     110 = RXB0 Interrupt
;     111 = RXB1 Interrupt
;+============================+

CANCTRL		equ	0x0F
CANSTAT		equ	0x0E
CANINTE		equ	0x2B
CANINTF		equ	0x2C
CNF1		equ	0x2A
CNF2		equ	0x29
CNF3		equ	0x28

SPI_RESET	equ	B'11000000'	;2510's RESET command


RXB0DLC		equ	0x65
RXBUF0		equ	B'01100110'	;Start of RXB0
RXM0SIDH	equ	0x20
RXM0SIDL	equ	0x21
RXB1DLC		equ	0x75
RXBUF1		equ	B'01110110'	;Start of RXB1
RXM1SIDH	equ	0x24
RXM1SIDL	equ	0x25

TXBUF0		equ	B'00100110'	;Start of TXB0
TXBUF1		equ	B'01000110'	;Start of TXB1 <- Only one used by current code
TXB1CTRL	equ	0x40	;TXB1 Control Register
TXBUF2		equ	B'01010110'	;Start of TXB2

	; Start at the reset vector
	org	0x000
	goto	Start
	org	0x004
	goto	IntService
	nop


Start

	banksel PORTB
	clrf	PORTB		;Clear PORTB

	banksel TRISB
	movlw	B'01000001'	;PORTB's I/O settings, with an input on RB0/INT
	movwf	TRISB
	movlw	B'11000000'	;PORTC's I/O settings
	movwf	TRISC
	movlw	0x00
	movwf	TRISD		;The data lines for the compact flash card
	movwf	TRISE
	;Address lines for Compact flash are A5-7
	; Bit 4 is the CF's reset strobe
	movlw	B'00010000'
	movwf	TRISA

;	banksel	OPTION_REG
;	movlw	0xA0
;	movwf	OPTION_REG
	
	banksel	PORTB
	movlw	B'00000010'	;Turn on Power LED, turn off MCP2510's chip select
	movwf	PORTB
	
	banksel	SPBRG
	movlw	B'10000001'
	movwf	SPBRG
	
	banksel	TXSTA
	movlw	B'00100110'	;Enable and active high-speed transmission
	movwf	TXSTA

	banksel	RCSTA
	clrf	RCSTA
	movlw	B'10010000'	;Enable receive, clear errors
	movwf	RCSTA

	banksel	PIE1
	bcf	PIR1, RCIF
	bsf	PIE1, RCIE	;RCIE -- interrupt on receive from PC
;	bsf	PIE1, INTE		;INTE -- external interrupt, from MCP2510
; NOTE:  Global Interrupts are NOT enabled HERE

	banksel	TXREG
	movlw	POWER_ON_MSG	;ASCII 'B'
	movwf	TXREG
	call	txwait

;+===========================+
;| SPI Init                  |
;+===========================+

;SSPCON is the sync Serial Port Control
; Bits 7 and 6 are Indication/Detection bits set by the PIC
; Bit 5 (Synscronous Seial Port Enable) must be 1 for SPI
; Bit 4 (Clock Polarity) sets the idle state for the CLK 
; Bit 3-0 Synchronous Serial Port Select 0000 - 0101 reserved for SPI's 
;various speeds
; It looks like, for the sake of safety, we'll be going at 2.5 MHz, or close to it.

	banksel	SSPCON
	movlw	B'00110000'	;Currently at 5MHz
	banksel	SSPSTAT
	clrf	SSPSTAT

;+==========================+
;| Buffer Config            |
;+==========================+

	banksel	PC_buff
	movlw	PC_buff
	movwf	PC_buff_in
	movwf	PC_buff_out
	clrf	PC_buff_ctr

	movlw	0x00
	movwf	PC_buff
	movwf	PC_buff+1
	movwf	PC_buff+2
	movwf	PC_buff+3
	movwf	PC_buff+4
	movwf	PC_buff+5
	movwf	PC_buff+6
	movwf	PC_buff+7
	movwf	PC_buff+8
	movwf	PC_buff+9
	movwf	PC_buff+0xA
	movwf	PC_buff+0xB
	movwf	PC_buff+0xC
	movwf	PC_buff+0xD
	movwf	PC_buff+0xE
	movwf	PC_buff+0xF
	movwf	PC_buff+10
	
	
;	banksel	TXREG
;	movlw	0x31
;	movwf	TXREG
;	call	txwait

	banksel	CAN_buff
	movlw	CAN_buff
	movwf	CAN_buff_in
	movwf	CAN_buff_out
	clrf	CAN_buff_ctr

;	banksel	TXREG
;	movlw	0x30
;	movwf	TXREG
;	call	txwait

CF_INIT
	;Test and see if there's a card inserted -- don't wait for one to be inserted
	; since the directions tell them to insert one before power-up

	banksel	PORTA
	bsf	CF_OE
	bsf	CF_WE
	nop			;Propogate signals (> 300 ns)
	
	btfss	CF_CD1		;Is there a card inserted?
	goto	CAN_INIT	;No?  Go set up the 2510

	;We have card!
	bsf	CF_INSERTED

	banksel	PORTA
	bsf	CF_RESET
	nop
	nop
	bcf	CF_RESET
	nop
	nop
	call wait
	call wait
	call wait
	call wait
	call wait
	call wait
	call wait
	call wait
	;LONG wait.  This may not be long enough, but it's probably OK

	

;+==========================+
;| MCP2510 Config           |
;+==========================+

CAN_INIT
;Initiate MCP2510 reset
	banksel	PORTB
	bcf	CAN_CS	;Hit the Chip Select

	movlw	SPI_RESET
	movwf	SSPBUF

	banksel	TXREG
	movlw	0x31
	movwf	TXREG
	call	txwait	

	banksel	SSPBUF
	movfw	SSPBUF

	banksel	PORTB
	bsf	CAN_CS

;	banksel	TXREG
;	movfw	0x43
;	movwf	TXREG

	;And now -- we wait!

	call	wait
	call	wait
	call	wait
	call	wait
	;This is probably excessive, but time is not
	;critical at this point...
	; Technically, this should be 128 Osc cycles from the 2510's point of view.
	; It's running on the same clock that the PIC is, divided by four

;	banksel	TXREG
;	movlw	0x32
;	movwf	TXREG
;	call	txwait

	; We need to set up the acceptance masks and filters here.
	; For the demo, we're using RXBUF0, so let's set its mask to all 0's

	banksel	SPI1
	movlw	RXM0SIDH
	movwf	SPI1
	movlw	0x00
	movwf	SPI2
	call	SPI_WRITE

	banksel	SPI1
	movlw	RXM0SIDL
	movwf	SPI1
	movlw	0x00
	movwf	SPI2
	call	SPI_WRITE

	; For that matter, let's turn off RXBUF1 by setting its mask to all 1's,
	; ensuring that nothing will match it.

	banksel	SPI1
	movlw	RXM1SIDH
	movwf	SPI1
	movlw	0xFF
	movwf	SPI2
	call	SPI_WRITE

	banksel	SPI1
	movlw	RXM1SIDL
	movwf	SPI1
	movlw	0xFF
	movwf	SPI2
	call	SPI_WRITE

	;The following settings I got from the sample code that Microchip made available.

	banksel	SPI1
	movlw	CNF1
	movwf	SPI1
	movlw	0x03
	movwf	SPI2
	call	SPI_WRITE

	banksel	SPI1
	movlw	CNF2
	movwf	SPI1
	movlw	0x90
	movwf	SPI2
	call	SPI_WRITE


	banksel	SPI1
	movlw	CNF3
	movwf	SPI1
	movlw	0x02
	movwf	SPI2
	call	SPI_WRITE
	; Lastly, let's tell the 2510 to interrupt us upon message receipt in RXB0

	banksel	SPI1
	movlw	CANINTE
	movwf	SPI1
	movlw	0x01
	movwf	SPI2
	call	SPI_WRITE

;***************************************************************************;
;+ Now that that's all done, let's set it up in loopback mode
;+
;+	banksel	SPI1
;+	movlw	CANCTRL
;+	movwf	SPI1
;+	movlw	B'01000000' ; Loopback Mode
;+	movwf	SPI2
;+	call	SPI_WRITE
;****************************************************************************

	banksel	SPI1
	movlw	CANCTRL
	movwf	SPI1
	movlw	B'01110000'	; Listen-only mode, and abort all pending transmissions
	movwf	SPI2