/*
 * Copyright 2005, 2006 Glen Overby.  All Rights Reserved.
 *
 * Atmel AVR Altitude-Only Altimeter based on a Tiny45
 *	- Sample data on 1 A/D @ 200hz, filter with a recursive average
 *	- software-driven serial port for debugging and detailed data
 *	- status on a Buzzer (in morse code)
 *	- Record Base and Peak voltages
 *
 *	Pinout: Tiny45
 *			reset	1	8	vcc
 *	Sensor	    ADC3 /PB3	2	7	PB2 SCK  / ADC1
 *	Buzzer	    ADC4 /PB4	3	6	PB1 MISO /	TxD
 *			  gnd	4	5	PB0 MOSI	Mode?
 *
 *		PB4		Buzzer
 *		PB3 (ADC3)	Pressure Sensor
 *		PB2		empty
 *		PB1		Mode: Run vs Report
 *		PB0		TxD
 *
 * ---------------------------------------------------------------------------
 *
 * Baud Rate Calculation
 *
 * _delay_loop_1( count )		3 cycles per loop
 * _delay_loop_2( count )		4 cycles per loop
 *
 *	Cycles per bit =  System clock / (Baudrate - Timer Prescaler)
 *
 *	CPU Clock	1mhz		8mhz
 *	Baud Rate	9600	19200	9600	19200
 *	Time Per Bit	9.6 ms	250us		
 *
 *	Cycles Per Bit	104.16	52.08		434
 *	delay_loop_1	34.722	17.36		144
 *	delay_loop_2	23		108.5	500?
 *
 *  2400 bps	= 2ms 2100us
 * 19200 bps	= 250us
 * Measured:
 * on/off	= 10us			1.2us
 * delay1(1)	= 25us			3us
 * delay1(10)	= 160us			8us
 * delay1(16)	= ?			30us
 *
 * delay2(1)				4us
 * delay2(10)				26us
 *
 * ---------------------------------------------------------------------------
 * Recursive Filter
 *	Described in David Schultz's 2002 NARAM paper.
 *	http://home.earthlink.net/~david.schultz/ under NAR R&D
 *
 *	P(n+1) = x * ADC + ( 1 - x ) * P(n)
 *
 * x = 1 gives the current value
 * x = 0 gives the old value (?)
 * x = 1/2 gives an average of the two values:
 *
 *	P(n+1) = (ADC + Pn) / 2
 *
 * Rearrange & Optimise:
 *
 *	P(n+1)	= x * ADC + Pn - x * Pn
 *		= Pn + x * ADC - x * Pn
 *		= Pn + x (ADC - Pn)
 *
 * Rearrange to get:
 *	P(n+1)	= P(n) + x (ADC - P(n))
 *
 * 200 samples/second, a weight of x = 1/32 worked well for him.
 *
 *	P(n+1)	= Pn + (ADC - Pn) / 32
 *
 * Spreadsheet: starting at zero, it takes 632 steps to hit 255.
 * Precision may be very important.  More bits would be better!
 *
 * Binary Point: 8 bits for fractional part.
 * A 'long' is 32 bits on an AVR.  Use that.
 *
 *	P(n+1)	= Pn + ((ADC<<8)>>5) - (Pn>>5)
 *		= Pn + (ADC<<3) - (Pn>>5)
 *
 *   or
 *	P(n+1)	= Pn + ( ( (ADC<<8) - Pn ) >> 5 )
 *
 *	old += ( (ADC << 3) - (old >> 5) )
 *
 * x = 1/32
 *	newalt = oldalt + ((( atod-data << 8) >> 5) -
 *			    (oldalt >> 5))
 *
 * 16 bits for fractional part
 *	P(n+1)	= Pn + ( ( (ADC<<16) - Pn ) >> 5 )
 *	old	+= (ADC << 11) - (old >> 5)
 *	
 */

# define F_CPU 8000000UL

#include <avr/io.h>
#include <avr/interrupt.h>
#include <util/delay.h>
#include <avr/eeprom.h>
#include <avr/pgmspace.h>
#include <string.h>
#include "morse.h"

/*
 * EEPROM Memory Map (in bytes)
 */

#define EE_STATUS	0
#define EE_GROUND	2
#define EE_APOGEE	4
#define EE_ATIME	6

/*
 * event bits:
 *	- 200hz		count for 10hz
 *	- 10hz		buzzer looks at state
 *	- 1hz		not sure what to do
 *	- a/d complete	run calculations
 */

volatile unsigned char	events;

#define	E_CLOCK	0x01
#define	E_ADC	0x02
#define	E_04	0x04
#define	E_08	0x08
#define	E_T1O	0x10
#define	E_T1C	0x20
#define	E_T0O	0x40
#define	E_T0C	0x80

/*
 *	Timer 0: 200hz
 */
ISR(SIG_OUTPUT_COMPARE0A)
{
	events |= E_CLOCK | E_T0C;
	ADCSRA |= _BV(ADSC);
}

#if 0
ISR(SIG_TIM0_OVF)		/* interrupts enabled */
{
	TIFR = _BV(TOV0);
	events |= E_CLOCK | E_T0O;
	ADCSRA |= _BV(ADSC);
}

ISR(SIG_TIM1_OVF)		/* interrupts enabled */
{
	TIFR = _BV(TOV1);

	events |= E_T1O;
}

ISR(SIG_TIM1_COMPA)
{
	/*TIFR = _BV(OCF1A);*/
	events |= E_T1C;
}
#endif

volatile unsigned int	adc_v0;		/* A/D input value */

ISR(SIG_ADC)
{
	unsigned char	c;
	unsigned int	i;

	c = ADCL;
	i = ADCH;
	i <<= 8;
	i |= (unsigned int)c;
	if (!(events & E_ADC)) {
		adc_v0 = i;
		events |= E_ADC;
	}
}


/*
 * Software serial port
 */
#define	SERIALPORT	PORTB
#define	TXBIT		0x02
/*#define BIT_DELAY	15*/	/* 1mhz 19200bps */
#define BIT_DELAY	100	/* 8mhz 19200bps */

void
tx(unsigned char c)
{
	unsigned char bc;	/* bit count */

	cli();
	SERIALPORT &= ~TXBIT;
	_delay_loop_2(BIT_DELAY);
	for (bc=8; bc > 0; bc--) {
		if (c & 0x01) {
			SERIALPORT |= TXBIT;
		} else {
			SERIALPORT &= ~TXBIT;
		}
		_delay_loop_2(BIT_DELAY);
		c >>= 1;
	}
	SERIALPORT |= TXBIT;
	sei();
	_delay_loop_2(BIT_DELAY);
	_delay_loop_2(BIT_DELAY);
}

void
sput(char *s)
{
	while (*s) {
		tx(*s);
		s++;
	}

	tx('\r');
	tx('\n');
}


/*
 * 16-bit hex output
 * Goal: more efficient than itoa
 *	s = 0xXXXX\0
 */
void
hex16(unsigned int i, char *str)
{
	char	c, count;

#ifdef X0
	str += 6;
	*str-- = '\0';
#else
	str += 5;
	*str-- = '\0';
	*str-- = ' ';
#endif
	for( count=4; count; count--) {
		c = i & 0xf;
		if( c > 9 )
			c += 0x37;
		else
			c += 0x30;
		*str-- = c;
		i >>= 4;
	}

#ifdef X0
	*str-- = 'x';
	*str-- = '0';
#endif
}

/*
 * Print to a buffer.
 */

char		str[22];
int		s;

void
px(int i)
{
	if (s > 16)
		return;
	hex16(i, &str[s]);
	s += 5;
}

void
pc(char c)
{
	str[s] = c;
	s++;
}

void
pflush()
{
	pc('\0');
	sput(str);
	s = 0;
}

/*
 * Peripheral initialization
 */
void
ioinit()
{

	events = 0;
	/*	PB5 PB4 PB3 PB2 PB1 PB0		Output = 1	*/
	/*	 I   O   I   I   O   I	*/
	/*	 I   O   O   I   O   I	*/
	/*	20  10   8   4   2   1  */
	PORTB = 0;
	DDRB = 0x12;
	/*DDRB = 0x1a;*/
	PORTB |= TXBIT;

	/*
	 * Set system clock divisor
	 */
	CLKPR = _BV(CLKPCE);
	CLKPR = 0x0;		/* Divisor = 0 */

	/*
	 * Timer 0 - 200hz
	 */
#if 1	/* 8 mhz */
	OCR0A = 156;			/* 8M / 256 = 31250 / 200 = 156 */
		/* 31 shows 5ms on & off times on scope */
	OCR0B = 157;
	TCCR0A = 0x02;			/* CTC mode is WGM01: = 010 */
	TCCR0B = 0x04;			/* clk/256 */
#else	/* 1 mhz */
#if 0			/* count up */
	OCR0A = 0xff;
	OCR0B = 0xff;
	TCCR0A = 0;
	TCCR0B = 0x03;			/* clk/64 */
	/* reload = 78 */
	reload = 0xff - 78;
#else			/* count down */
	OCR0A = 19; /*78;*/
	OCR0B = 0xff;
	TCCR0A = 0x02;			/* CTC mode is WGM01: = 010 */
	TCCR0B = 0x03;			/* clk/64 */
#endif
#endif

#if 0
	TCCR1 = 0x88;	/* CTC1 | CK/128 */
	OCR1A = 39;	/* >>> OCF1A */
	OCR1B = 42;
	OCR1C = 39;	/* resets cntr 1? */
#endif

	TIMSK = _BV(OCIE0A) | _BV(OCIE0B) | _BV(TOIE0);
/* >>> buggy?  Only an interrupt handler for OCIE0A is provided */

	/*
	 * A/D converter
	 */
	ADMUX = 0x03;				/* REFS = Vcc  */
	/*ADMUX = 0x0c;*/
	ADCSRA = _BV(ADEN) | _BV(ADIE) | 0x6 ;	/* ADPS = / 64 */
	ADCSRA |= _BV(ADSC);
	sei();
}

/*
 * Buzzer with cycle counter
 */

#define	BUZZERMASK	0x10

char		bzcount;	/* Count */
char		bzon, bzoff;	/* on & off time */
char		bz;		/* timer time */

void
buzzer(char count, char on, char off)
{
	bzcount = count;
	bz = bzon = on;
	bzoff = off;

	PORTB |= BUZZERMASK;
}

void
buzz()
{
	if (PORTB & BUZZERMASK) {
		PORTB &= ~BUZZERMASK;
		bz = bzoff;
		if (bzcount == 1)
			bz += bzoff;
		/*tx('B');*/
	} else {
		if (--bzcount) {
			PORTB |= BUZZERMASK;
			bz = bzon;
			/*tx('b');*/
		}
	}
}

/*
 * Morse code output to a buzzer
 */

unsigned char	word;

void
buzzm()
{
	if ((PORTB & BUZZERMASK)) {
		PORTB &= ~BUZZERMASK;
		bz = bzon;
		if (word == 0x80)
			bz = bzoff+bzoff+bzoff;
		/*tx('B');*/
	} else {
		if( word != 0x80 ) {
			bz = ( word & 0x80 ) ? bzoff : bzon;
			PORTB |= BUZZERMASK;
			word <<= 1;
			/*tx('b');*/
		} else {
			bzcount = 0;
		}
	}
}

void
morse(unsigned char w)
{
	word = w;
	bzcount = 1;
	PORTB &= ~BUZZERMASK;
	buzzm();
}

/*
 * Number to Morse Code translation table
 */
prog_int8_t digits[] = {
	m0, m1, m2, m3, m4, m5, m6, m7, m8, m9
};

/*
 * Altitude Table
 *
 * a table is a compromise with a logarithm for the altitude.  
 * With adequate memory, the altitude can be represented close enough for my
 * needs.  Anything more detailed should simply use Hpa and calulate it
 * after the flight.
 */

prog_int16_t alt[] = {
51246, /* 0x0 0 0.0000 V 10.3314 hpa 51245.8521 ft -51245.9 delta */
50002, /* 0x8 8 0.0391 V 11.0692 hpa 50001.5923 ft 1244.3 delta */
48823, /* 0x10 16 0.0781 V 11.8069 hpa 48822.7672 ft 1178.8 delta */
47702, /* 0x18 24 0.1172 V 12.5446 hpa 47702.1523 ft 1120.6 delta */
46634, /* 0x20 32 0.1562 V 13.2823 hpa 46633.6907 ft 1068.5 delta */
45612, /* 0x28 40 0.1953 V 14.0201 hpa 45612.2510 ft 1021.4 delta */
44633, /* 0x30 48 0.2344 V 14.7578 hpa 44633.4454 ft 978.8 delta */
43693, /* 0x38 56 0.2734 V 15.4955 hpa 43693.4908 ft 940.0 delta */
42789, /* 0x40 64 0.3125 V 16.2332 hpa 42789.1010 ft 904.4 delta */
41917, /* 0x48 72 0.3516 V 16.9710 hpa 41917.4022 ft 871.7 delta */
41076, /* 0x50 80 0.3906 V 17.7087 hpa 41075.8659 ft 841.5 delta */
40262, /* 0x58 88 0.4297 V 18.4464 hpa 40262.2546 ft 813.6 delta */
39475, /* 0x60 96 0.4688 V 19.1841 hpa 39474.5785 ft 787.7 delta */
38711, /* 0x68 104 0.5078 V 19.9219 hpa 38711.0597 ft 763.5 delta */
37970, /* 0x70 112 0.5469 V 20.6596 hpa 37970.1025 ft 741.0 delta */
37250, /* 0x78 120 0.5859 V 21.3973 hpa 37250.2692 ft 719.8 delta */
36550, /* 0x80 128 0.6250 V 22.1350 hpa 36550.2595 ft 700.0 delta */
35869, /* 0x88 136 0.6641 V 22.8728 hpa 35868.8932 ft 681.4 delta */
35205, /* 0x90 144 0.7031 V 23.6105 hpa 35205.0958 ft 663.8 delta */
34558, /* 0x98 152 0.7422 V 24.3482 hpa 34557.8861 ft 647.2 delta */
33926, /* 0xa0 160 0.7812 V 25.0859 hpa 33926.3653 ft 631.5 delta */
33310, /* 0xa8 168 0.8203 V 25.8237 hpa 33309.7080 ft 616.7 delta */
32707, /* 0xb0 176 0.8594 V 26.5614 hpa 32707.1543 ft 602.6 delta */
32118, /* 0xb8 184 0.8984 V 27.2991 hpa 32118.0032 ft 589.2 delta */
31542, /* 0xc0 192 0.9375 V 28.0368 hpa 31541.6061 ft 576.4 delta */
30977, /* 0xc8 200 0.9766 V 28.7746 hpa 30977.3620 ft 564.2 delta */
30425, /* 0xd0 208 1.0156 V 29.5123 hpa 30424.7126 ft 552.6 delta */
29883, /* 0xd8 216 1.0547 V 30.2500 hpa 29883.1387 ft 541.6 delta */
29352, /* 0xe0 224 1.0938 V 30.9877 hpa 29352.1560 ft 531.0 delta */
28831, /* 0xe8 232 1.1328 V 31.7254 hpa 28831.3127 ft 520.8 delta */
28320, /* 0xf0 240 1.1719 V 32.4632 hpa 28320.1858 ft 511.1 delta */
27818, /* 0xf8 248 1.2109 V 33.2009 hpa 27818.3794 ft 501.8 delta */
27326, /* 0x100 256 1.2500 V 33.9386 hpa 27325.5219 ft 492.9 delta */
26841, /* 0x108 264 1.2891 V 34.6763 hpa 26841.2644 ft 484.3 delta */
26365, /* 0x110 272 1.3281 V 35.4141 hpa 26365.2786 ft 476.0 delta */
25897, /* 0x118 280 1.3672 V 36.1518 hpa 25897.2551 ft 468.0 delta */
25437, /* 0x120 288 1.4062 V 36.8895 hpa 25436.9023 ft 460.4 delta */
24984, /* 0x128 296 1.4453 V 37.6272 hpa 24983.9448 ft 453.0 delta */
24538, /* 0x130 304 1.4844 V 38.3650 hpa 24538.1222 ft 445.8 delta */
24099, /* 0x138 312 1.5234 V 39.1027 hpa 24099.1882 ft 438.9 delta */
23667, /* 0x140 320 1.5625 V 39.8404 hpa 23666.9092 ft 432.3 delta */
23241, /* 0x148 328 1.6016 V 40.5781 hpa 23241.0639 ft 425.8 delta */
22821, /* 0x150 336 1.6406 V 41.3159 hpa 22821.4421 ft 419.6 delta */
22408, /* 0x158 344 1.6797 V 42.0536 hpa 22407.8443 ft 413.6 delta */
22000, /* 0x160 352 1.7188 V 42.7913 hpa 22000.0804 ft 407.8 delta */
21598, /* 0x168 360 1.7578 V 43.5290 hpa 21597.9697 ft 402.1 delta */
21201, /* 0x170 368 1.7969 V 44.2668 hpa 21201.3399 ft 396.6 delta */
20810, /* 0x178 376 1.8359 V 45.0045 hpa 20810.0269 ft 391.3 delta */
20424, /* 0x180 384 1.8750 V 45.7422 hpa 20423.8740 ft 386.2 delta */
20043, /* 0x188 392 1.9141 V 46.4799 hpa 20042.7314 ft 381.1 delta */
19666, /* 0x190 400 1.9531 V 47.2177 hpa 19666.4563 ft 376.3 delta */
19295, /* 0x198 408 1.9922 V 47.9554 hpa 19294.9118 ft 371.5 delta */
18928, /* 0x1a0 416 2.0312 V 48.6931 hpa 18927.9671 ft 366.9 delta */
18565, /* 0x1a8 424 2.0703 V 49.4308 hpa 18565.4967 ft 362.5 delta */
18207, /* 0x1b0 432 2.1094 V 50.1686 hpa 18207.3806 ft 358.1 delta */
17854, /* 0x1b8 440 2.1484 V 50.9063 hpa 17853.5036 ft 353.9 delta */
17504, /* 0x1c0 448 2.1875 V 51.6440 hpa 17503.7550 ft 349.7 delta */
17158, /* 0x1c8 456 2.2266 V 52.3817 hpa 17158.0289 ft 345.7 delta */
16816, /* 0x1d0 464 2.2656 V 53.1195 hpa 16816.2232 ft 341.8 delta */
16478, /* 0x1d8 472 2.3047 V 53.8572 hpa 16478.2400 ft 338.0 delta */
16144, /* 0x1e0 480 2.3438 V 54.5949 hpa 16143.9850 ft 334.3 delta */
15813, /* 0x1e8 488 2.3828 V 55.3326 hpa 15813.3676 ft 330.6 delta */
15486, /* 0x1f0 496 2.4219 V 56.0703 hpa 15486.3004 ft 327.1 delta */
15163, /* 0x1f8 504 2.4609 V 56.8081 hpa 15162.6994 ft 323.6 delta */
14842, /* 0x200 512 2.5000 V 57.5458 hpa 14842.4834 ft 320.2 delta */
14526, /* 0x208 520 2.5391 V 58.2835 hpa 14525.5745 ft 316.9 delta */
14212, /* 0x210 528 2.5781 V 59.0212 hpa 14211.8971 ft 313.7 delta */
13901, /* 0x218 536 2.6172 V 59.7590 hpa 13901.3787 ft 310.5 delta */
13594, /* 0x220 544 2.6562 V 60.4967 hpa 13593.9489 ft 307.4 delta */
13290, /* 0x228 552 2.6953 V 61.2344 hpa 13289.5399 ft 304.4 delta */
12988, /* 0x230 560 2.7344 V 61.9721 hpa 12988.0862 ft 301.5 delta */
12690, /* 0x238 568 2.7734 V 62.7099 hpa 12689.5244 ft 298.6 delta */
12394, /* 0x240 576 2.8125 V 63.4476 hpa 12393.7932 ft 295.7 delta */
12101, /* 0x248 584 2.8516 V 64.1853 hpa 12100.8334 ft 293.0 delta */
11811, /* 0x250 592 2.8906 V 64.9230 hpa 11810.5876 ft 290.2 delta */
11523, /* 0x258 600 2.9297 V 65.6608 hpa 11523.0001 ft 287.6 delta */
11238, /* 0x260 608 2.9688 V 66.3985 hpa 11238.0173 ft 285.0 delta */
10956, /* 0x268 616 3.0078 V 67.1362 hpa 10955.5869 ft 282.4 delta */
10676, /* 0x270 624 3.0469 V 67.8739 hpa 10675.6584 ft 279.9 delta */
10398, /* 0x278 632 3.0859 V 68.6117 hpa 10398.1829 ft 277.5 delta */
10123, /* 0x280 640 3.1250 V 69.3494 hpa 10123.1128 ft 275.1 delta */
9850, /* 0x288 648 3.1641 V 70.0871 hpa 9850.4019 ft 272.7 delta */
9580, /* 0x290 656 3.2031 V 70.8248 hpa 9580.0056 ft 270.4 delta */
9312, /* 0x298 664 3.2422 V 71.5626 hpa 9311.8804 ft 268.1 delta */
9046, /* 0x2a0 672 3.2812 V 72.3003 hpa 9045.9840 ft 265.9 delta */
8782, /* 0x2a8 680 3.3203 V 73.0380 hpa 8782.2756 ft 263.7 delta */
8521, /* 0x2b0 688 3.3594 V 73.7757 hpa 8520.7152 ft 261.6 delta */
8261, /* 0x2b8 696 3.3984 V 74.5135 hpa 8261.2642 ft 259.5 delta */
8004, /* 0x2c0 704 3.4375 V 75.2512 hpa 8003.8850 ft 257.4 delta */
7749, /* 0x2c8 712 3.4766 V 75.9889 hpa 7748.5408 ft 255.3 delta */
7495, /* 0x2d0 720 3.5156 V 76.7266 hpa 7495.1960 ft 253.3 delta */
7244, /* 0x2d8 728 3.5547 V 77.4644 hpa 7243.8162 ft 251.4 delta */
6994, /* 0x2e0 736 3.5938 V 78.2021 hpa 6994.3674 ft 249.4 delta */
6747, /* 0x2e8 744 3.6328 V 78.9398 hpa 6746.8168 ft 247.6 delta */
6501, /* 0x2f0 752 3.6719 V 79.6775 hpa 6501.1325 ft 245.7 delta */
6257, /* 0x2f8 760 3.7109 V 80.4153 hpa 6257.2833 ft 243.8 delta */
6015, /* 0x300 768 3.7500 V 81.1530 hpa 6015.2389 ft 242.0 delta */
5775, /* 0x308 776 3.7891 V 81.8907 hpa 5774.9696 ft 240.3 delta */
5536, /* 0x310 784 3.8281 V 82.6284 hpa 5536.4467 ft 238.5 delta */
5300, /* 0x318 792 3.8672 V 83.3661 hpa 5299.6420 ft 236.8 delta */
5065, /* 0x320 800 3.9062 V 84.1039 hpa 5064.5280 ft 235.1 delta */
4831, /* 0x328 808 3.9453 V 84.8416 hpa 4831.0782 ft 233.4 delta */
4599, /* 0x330 816 3.9844 V 85.5793 hpa 4599.2663 ft 231.8 delta */
4369, /* 0x338 824 4.0234 V 86.3170 hpa 4369.0668 ft 230.2 delta */
4140, /* 0x340 832 4.0625 V 87.0548 hpa 4140.4551 ft 228.6 delta */
3913, /* 0x348 840 4.1016 V 87.7925 hpa 3913.4066 ft 227.0 delta */
3688, /* 0x350 848 4.1406 V 88.5302 hpa 3687.8979 ft 225.5 delta */
3464, /* 0x358 856 4.1797 V 89.2679 hpa 3463.9057 ft 224.0 delta */
3241, /* 0x360 864 4.2188 V 90.0057 hpa 3241.4074 ft 222.5 delta */
3020, /* 0x368 872 4.2578 V 90.7434 hpa 3020.3810 ft 221.0 delta */
2801, /* 0x370 880 4.2969 V 91.4811 hpa 2800.8048 ft 219.6 delta */
2583, /* 0x378 888 4.3359 V 92.2188 hpa 2582.6578 ft 218.1 delta */
2366, /* 0x380 896 4.3750 V 92.9566 hpa 2365.9193 ft 216.7 delta */
2151, /* 0x388 904 4.4141 V 93.6943 hpa 2150.5692 ft 215.4 delta */
1937, /* 0x390 912 4.4531 V 94.4320 hpa 1936.5878 ft 214.0 delta */
1724, /* 0x398 920 4.4922 V 95.1697 hpa 1723.9557 ft 212.6 delta */
1513, /* 0x3a0 928 4.5312 V 95.9075 hpa 1512.6541 ft 211.3 delta */
1303, /* 0x3a8 936 4.5703 V 96.6452 hpa 1302.6645 ft 210.0 delta */
1094, /* 0x3b0 944 4.6094 V 97.3829 hpa 1093.9689 ft 208.7 delta */
887, /* 0x3b8 952 4.6484 V 98.1206 hpa 886.5496 ft 207.4 delta */
680, /* 0x3c0 960 4.6875 V 98.8584 hpa 680.3892 ft 206.2 delta */
475, /* 0x3c8 968 4.7266 V 99.5961 hpa 475.4708 ft 204.9 delta */
272, /* 0x3d0 976 4.7656 V 100.3338 hpa 271.7778 ft 203.7 delta */
69, /* 0x3d8 984 4.8047 V 101.0715 hpa 69.2940 ft 202.5 delta */
-132, /* 0x3e0 992 4.8438 V 101.8093 hpa -131.9966 ft 201.3 delta */
-332, /* 0x3e8 1000 4.8828 V 102.5470 hpa -332.1096 ft 200.1 delta */
-531, /* 0x3f0 1008 4.9219 V 103.2847 hpa -531.0602 ft 199.0 delta */
-729, /* 0x3f8 1016 4.9609 V 104.0224 hpa -728.8635 ft 197.8 delta */
};

/*
 * Altitude Lookup
 *
 * Input is a 10-bit altitude. It should already be rounded.
 *
 * The table holds every 8th value.  The output altitude can be imprecise
 * because the difference between two values is a fraction, and this uses
 * integer arithmetic.
 *
 * Solution:
 *	j = i - j;	simple integer 
 *	j <<= 8;	fixed point: 8 bit fraction 
 *	j >>= 3;	divide by 8 
 *	k = 0;		sucker multiply 
 *	for (l = value & 0x7; l--; )
 *		k += j;
 *	j = k >> 8;	convert to simple integer 
 *	if (k & 0x80)
 *		j++;	round 
 *	i -= j;		finish calculation 
 */
int
altitude(int value)
{
	int i, j, l, t1, t2;
	long a, b;

	i = value >> 3;		/* value/8 = index */
	t1 = pgm_read_word_near(&alt[i]);
	/*pc('$');
	px(i);
	px(t1);*/

	/*
	 * if value & 0x7 != 0
	 *	read (value >> 3) and ((value >> 3) + 1) and interpolate
	 */
	if (value & 0x7) {
		t2 = pgm_read_word_near(&alt[i+1]);
		/*px(t2);*/
		a = t1 - t2;	/* simple integer */
		a <<= 8;	/* fixed point: 8 bit fraction */
		a >>= 3;	/* divide by 8 */
		b = 0;		/* sucker multiply */
		for (l = value & 0x7; l--; )
			b += a;
		j = b >> 8;	/* convert to simple integer */
		if (a & 0x80)
			j++;	/* round */
		/*px(j);*/
		t1 -= j;		/* finish calculation */
	}
	return t1;
}


/*
 * Binary Coded Decimal
 * Brute force method, with a fixed number of digits
 */

char	bcdvalue[5];

int
bcdigit(int v, int i, int j)
{
	bcdvalue[i] = 0;
	while ( v >= j) {
		bcdvalue[i]++;
		v -= j;
	}

	return v;
}

void
bcd(int v)
{
	v = bcdigit(v, 0, 10000);
	v = bcdigit(v, 1, 1000);
	v = bcdigit(v, 2, 100);
	v = bcdigit(v, 3, 10);
	v = bcdigit(v, 4, 1);
}


int
main()
{
	unsigned char	fstate;
#define	S_R0		0
#define	S_STARTUP	1
#define	S_GROUND	2
#define	S_ASCENT	3
#define	S_APOGEE	4
#define	S_DONE		5	/* reporting */

	char		cnt10hz;
	unsigned char	report;
	unsigned char	rstate;
#define R_R0		0
#define	R_STARTUP	1
#define	R_GROUND	2
#define	R_LAUNCH	3
#define	R_APOGEE	4
#define	R_ALT		5
#define	R_BCDALT	6
#define	R_DONE		7

	unsigned char	bstate;
#define	B_LAST		0
#define	B_FSTATE	1
#define	B_DONE		2

	int		timer;
	long		adc_last0;		/* Last A/D value */
	long		adc_ground;		/* "ground" value */
	long		adc_apogee;		/* apogee value */
	int		alt;			/* apogee altitude */
	int		ascent_time;		/* "up" time */
	int		t;
	int		b;

	ioinit();
	sei();
	tx('!');

	adc_last0 = adc_ground = adc_apogee = 0;
	ascent_time = 0;
	fstate = rstate = bstate = 0;
	cnt10hz = 20;
	timer = 0;
	s = 0;
	report = 200;

	bzon = 1;
	bzoff = 3;
	morse(0x01);

	adc_ground = eeprom_read_word((uint16_t*)EE_GROUND);
	adc_apogee = eeprom_read_word((uint16_t*)EE_APOGEE);
	alt = altitude(adc_apogee);
	/* >>> pflush(); <<< */
	alt -= altitude(adc_ground);
	/* >>> pflush(); <<< */
	pc('R');
	px(adc_ground);
	px(adc_apogee);
	px(alt);
	pflush();	/* >>> */

	/* buzzer: altitude */
	bcd(alt);
	for(b = 0; bcdvalue[b] == 0; b++)
		;

	while (1) {
		sei();
		if (events & E_CLOCK) {
			events &= ~E_CLOCK;
			/*tx('t');*/
			if (--cnt10hz == 0) {
				/*tx('T');*/
				cnt10hz = 20;
				timer++;
				if (bzcount && --bz == 0) {
					buzzm();
				}
			}
			if (report) {
				report--;
			}
		}

		if (events & E_ADC) {
			adc_last0 += ((long)( adc_v0 << 3 )) -
					(adc_last0 >> 5);
			cli();
			events &= ~E_ADC;
			sei();
			/*tx('&');*/

			switch(fstate) {
			/* 
			 * Wait for pressure average to stabilize
			 */
			case S_R0:
				fstate = S_STARTUP;
				break;
			case S_STARTUP:
				if (timer > 10) {
					adc_ground = adc_last0;
					adc_apogee = adc_ground - (3<<8);
					tx('g');
					fstate = S_GROUND;
				}
				break;
			/* Watch for launch */
			case S_GROUND:
				/* overload _apogee as the launch detect alt */
				if (adc_last0 < adc_apogee) {
					fstate = S_ASCENT;
					timer = 0;
					ascent_time = 0;
					tx('l');
				}
				break;
			/* Watch for Apogee */
			case S_ASCENT:
				ascent_time++;
				if (adc_last0 < adc_apogee) {
					adc_apogee = adc_last0;
					tx('+');
				} else if (adc_last0 > (adc_apogee + 0x300)) {
					fstate = S_APOGEE;
					ascent_time = timer;
					tx('a');
					eeprom_write_word((uint16_t*)EE_GROUND,
						adc_ground>>8);
					eeprom_write_word((uint16_t*)EE_APOGEE,
						adc_apogee>>8);
					eeprom_write_word((uint16_t*)EE_ATIME,
						ascent_time);
					alt = altitude(adc_apogee>>8);
					alt -= altitude(adc_ground>>8);
					bcd(alt);
					for(b = 0; bcdvalue[b] == 0; b++)
						;
				}
				break;
			case S_APOGEE:
				fstate++;
				break;
			}
		}

		/*
		 * Serial Port Status Reporting
		 *
		 * - Last Altitude & Time
		 * - Current Ground Level
		 * - This Flight's Altitude & Time
		 */
		if (s == 0) {
			if (report == 0) {
				report = 200;
			}
			switch (rstate) {
			case S_R0:
			case R_STARTUP:	/* Startup (S_STARTUP) */
				/* when waiting to pass S_STARTUP:
				 *	buzzer 1hz
				 *	a/d value
				 */
				/* Serial: ground level */
				if (report == 200) {
					pc('S');
					px(adc_last0>>4);
					tx(str[0]);
					s = 1;
				}
				if (fstate > S_STARTUP) {
					rstate = R_GROUND;
					pc('G');
					px(adc_ground);
					tx(str[0]);
					s = 1;
				}
				break;
			case R_GROUND:	/* Wait for launch */
				/* short beep every n seconds */
				if (fstate > S_GROUND) {
					/* buzzer: fast */
					rstate = R_LAUNCH;
					tx('L');
				}
				break;
			case R_LAUNCH:	/* Launch Detected */
				if (fstate >= S_APOGEE) {
					rstate = R_APOGEE;
				}
				break;
			case R_APOGEE:
				pc('A');
				px(adc_apogee);
				tx(str[0]);
				s = 1;
				rstate++;
				break;
			case R_ALT:
				pc('H');
				px(alt);
				tx(str[0]);
				s = 1;
				rstate++;
				break;
			case R_BCDALT:
				pc('B');
				for(t = 0; t < 5; t++) {
					pc('0' + bcdvalue[t]);
				}
				pc('\0');
				tx(str[0]);
				s = 1;
				rstate++;
				break;
			case R_DONE:
				break;
			}	
		} else {
			tx(str[s]);
			s++;
			if (str[s] == '\0') {
				str[1] = '\r';
				str[2] = '\n';
				str[3] = '\1';
				s = 1;
			} else if (str[s] == '\1') {
				s = 0;
			}
		}
		/*
		 * Status reporting by buzzer
		 */
		if (bzcount == 0) {
			switch(bstate) {
			case B_LAST:
				/* last altitude */
				if (b < 5) {
					t = bcdvalue[b];
					morse(pgm_read_byte_near(&digits[t]));
					b++;
				} else {
					bstate = B_FSTATE;
					morse(mStop);
				}
				break;
			case B_FSTATE:
				switch(fstate) {
				case S_STARTUP:	morse(mS);	break;
				case S_GROUND:  morse(mE);	break;
				case S_ASCENT:	morse(mH);	break;
				case S_APOGEE:	morse(mA);	break;
				case S_DONE:
					morse(mA);
					bstate = B_DONE;
					break;
				}
				break;
			case B_DONE:
				/*
				 * buzzer altitude
				 */
				if (b >= 5) {
					for(b = 0; bcdvalue[b] == 0; b++)
						;
					morse(mStop);
				} else {
					t = bcdvalue[b];
					morse(pgm_read_byte_near(&digits[t]));
					b++;
				}
				break;
			}
		}
	}
}