/* addrs: SSSEEEEE
			 *           8 -> extended addr
			 *          14 -> unused
			 */
#define CANA_TIME		0x10080000
#define CANA_DISCOVERY		0x4c080000
#define CANA_LIGHT		0xcc080000
#define CANA_LIGHT_F(src,dst)	(CANA_LIGHT | (((src) << 12) & 0x3f) | ((dst) & 0xfff))
#define CANA_SENSOR		0xe6080000
#define CANA_SENSOR_F(src)	(CANA_SENSOR | ((src) & 0xfff))

#ifndef R0KET
#define spi_ss(x)	PORTB = ((x) << B_SS) | 0x3;

static volatile bool canint = false;

ISR(INT0_vect)
{
	canint = true;
}

static uint8_t spi_wrrd(uint8_t out)
{
	SPDR = out;
	while (!(SPSR & (1 << SPIF)))
		;
	return SPDR;
}

static void spi_performpgm(const uint8_t * PROGMEM cmds, uint8_t len)
{
	const uint8_t * PROGMEM end = cmds + len;
	uint8_t c;

	spi_ss(0);
	while (cmds < end) {
		c = pgm_read_byte(cmds);
		spi_wrrd(c);
		cmds++;
	}
	spi_ss(1);
}
#endif
#define spi_perform(...) do { \
	static const uint8_t _mycmds[] PROGMEM = { __VA_ARGS__ }; \
	spi_performpgm(_mycmds, sizeof(_mycmds)); } while (0)

/* CAN configuration:
 *
 * CNF1	SJW	= 1TQ	00xxxxxx
 * 	BRP	= /12	xx001011	(16 MHz assumed)
 * 	= 0x0b
 * CNF2 BTLMODE = cfg	1xxxxxxx
 * 	SAM	= once	x0xxxxxx
 * 	PS1	= 1TQ	xx000xxx
 * 	prop	= 2TQ	xxxxx001
 * 	= 0x81
 * CNF3	WAKFIL	= off	x0xxxxxx
 * 	PS2	= 2TQ	xxxxx001
 * 	= 0x01
 */

#define MCP2515_WRITE	0x02
#define MCP2515_READ	0x03
#define MCP2515_RTS	0x80
#define MCP2515_WRTXB	0x40
#define MCP2515_WRTXB_DATA	0x01
#define MCP2515_WRTXB_TXB0	0x00
#define MCP2515_WRTXB_TXB1	0x02
#define MCP2515_WRTXB_TXB2	0x04

#define A_CNF3		0x28
#define A_CANINTF	0x2c
#define A_CANCTRL	0x2f
#define A_TXB0CTRL	0x30
#define A_TXB0SIDH	0x31
#define A_RXB1CTRL	0x70

static void can_init(void)
{
	spi_perform(MCP2515_WRITE, A_CANCTRL,
		0x80);	/* CANCTRL: config mode */
#ifdef R0KET
#define CNF1	0x05	/* 8 MHz crystal, divide by 6 */
#else
#define CNF1	0x0b	/* 16 MHz crystal, divide by 12 */
#endif
	spi_perform(MCP2515_WRITE, A_CNF3,
		0x01,	/* CNF3 */
		0x81,	/* CNF2 */
		CNF1,	/* CNF1 */
		0xa7	/* CANINTE: MERRE, ERRIE, TX0IE, RX1IE, RX0IE */
	);
	spi_perform(MCP2515_WRITE, A_RXB1CTRL,
		0x60);	/* x, RXM, x, RXRTR, FILHIT */
	spi_perform(MCP2515_WRITE, A_CANCTRL,
		0x00);	/* CANCTRL: normal mode */
}

static uint8_t can_CANSTAT(void)
{
	uint8_t canstat;

	spi_ss(0);
	spi_wrrd(0x03);
	spi_wrrd(0x2e);	/* addr(CANCTRL) */
	canstat = spi_wrrd(0xff);	/* CANSTAT */
	spi_ss(1);
	uart_puts("can: CANSTAT ");
	uart_puthex(canstat);
	uart_puts("\n");
	return canstat;
}

/* daddr:
 *   31-24	ID 10:3
 *   23-16	ID 2:0, x, EXIDE, x, EID17:16
 *   15- 8	EID 15:8
 *    7- 0	EID  7:0
 */
static void can_send(uint32_t daddr, uint8_t len, uint8_t *data)
{
	spi_ss(0);
	spi_wrrd(MCP2515_WRTXB | MCP2515_WRTXB_TXB0);
	spi_wrrd((daddr >> 24) & 0xff);
	spi_wrrd((daddr >> 16) & 0xff);
	spi_wrrd((daddr >>  8) & 0xff);
	spi_wrrd((daddr >>  0) & 0xff);
	spi_wrrd(len);
	while (len--)
		spi_wrrd(*data++);
	spi_ss(1);
	spi_perform(MCP2515_RTS | 0x01);
}

#ifndef R0KET
union {
	uint8_t b[4];
	uint32_t u;
} can_rx_addr;
uint8_t can_rx_dlc, can_rx_data[8];

static void can_rxh(uint8_t buffer)
{
	uint8_t c, byte;

	if (buffer)
		uart_puts("can: RX1IF\n");
	else
		uart_puts("can: RX0IF\n");
	spi_ss(0);
	spi_wrrd(0x90 + 0x04 * buffer);
	c = 0;
#define rdaddr() byte = spi_wrrd(0xff); uart_puthex(byte); can_rx_addr.b[c++] = byte
	rdaddr();
	rdaddr();
	rdaddr();
	rdaddr();
	can_rx_dlc = spi_wrrd(0xff);
	uart_puthex(can_rx_dlc);
	uart_puts("\n");
	for (c = 0; c < (can_rx_dlc & 0x0f); c++) {
		byte = spi_wrrd(0xff);
		can_rx_data[c] = byte;
		uart_puthex(byte);
	}
	uart_puts("\n");
	spi_ss(1);
}

static void can_int(void)
{
	uint8_t canintf, eflg, canstat;

#ifdef HAVE_TICK
	uart_puttick();
#endif
	uart_puts("can: irqh<");

	spi_ss(0);
	spi_wrrd(MCP2515_READ);
	spi_wrrd(A_CANINTF);
	canintf	= spi_wrrd(0xff);
	eflg	= spi_wrrd(0xff);
	canstat = spi_wrrd(0xff);
	spi_ss(1);

	uart_puthex(canintf);
	uart_puthex(eflg);
	uart_puthex(canstat);
	uart_puts(">\n");

	if (canintf & 0x80 || canintf & 0x04) {
		uint8_t txb0ctrl;
		spi_ss(0);
		spi_wrrd(MCP2515_READ);
		spi_wrrd(A_TXB0CTRL);
		txb0ctrl = spi_wrrd(0xff);
		spi_ss(1);

		/* clear RTS */
		if (txb0ctrl & 0x08) {
			spi_ss(0);
			spi_wrrd(MCP2515_WRITE);
			spi_wrrd(A_TXB0CTRL);
			spi_wrrd(0x00);
			spi_ss(1);
		}
	}
	if (canintf & 0x01)
		can_rxh(0);
	if (canintf & 0x02)
		can_rxh(1);

	spi_perform(MCP2515_WRITE, A_CANINTF, 0x00, 0x00);
}
#endif

static void can_preinit(void)
{
	spi_ss(1);
#ifndef R0KET
	DDRB |= (1 << B_SCK) | (1 << B_MOSI) | (1 << B_SS);

	/* divisor: 0 0 0 = fosc / 4 = 2 MHz */
	SPCR = (1 << SPE) | (1 << MSTR);

	/* INT0 */
	EICRA = (1 << ISC01);
	EIMSK = (1 << INT0);

	_delay_ms(5);
#endif

	/* chip reset */
	spi_ss(0);
	spi_wrrd(0xc0);
	spi_ss(1);

	_delay_ms(5);

	spi_ss(0);
	spi_wrrd(0xb0);
	uint8_t status = spi_wrrd(0xff);
	spi_ss(1);
	uart_puts("can: status ");
	uart_puthex(status);
	uart_puts("\n");
}