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#include "common.h"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <avr/io.h>
#include <avr/interrupt.h>
#include <avr/sleep.h>

#include "i2c.h"
#include "gyro.h"

/* device address */
#define L3GD20 0b11010100
/* registers */
#define L3GD20_WHOAMI 0xf
#define L3GD20_CTRLREG1 0x20
#define L3GD20_CTRLREG3 0x22
#define L3GD20_CTRLREG4 0x23
#define L3GD20_CTRLREG5 0x24
#define L3GD20_OUTZ 0x2c

/* raw z value */
static volatile int16_t zval = 0;
/* accumulated z value */
static int32_t zaccum = 0;
/* calculated zticks */
static int16_t zticks = 0;

#define STOPPED 0
#define START_REQUEST 1
#define STARTING 2
#define STOPPING 4
#define READING 5
#define IDLE 6
static uint8_t state = STOPPED;
static bool shouldStop = false;

/* data ready interrupt
 */
ISR(PCINT0_vect) {
	const bool interrupt = (PINB >> PINB1) & 0x1;
	/* high-active */
	if (interrupt) {
		enableWakeup (WAKE_GYRO);
	} else {
		disableWakeup (WAKE_GYRO);
	}
}

void gyroInit () {
	/* set PB1 to input */
	DDRB = DDRB & ~((1 << DDB1));
	/* enable interrupt PCI0 */
	PCICR = PCICR | (1 << PCIE0);
	/* enable interrupts on PB1/PCINT1 */
	PCMSK0 = (1 << PCINT1);
}

void gyroStart () {
	assert (state == STOPPED);
	state = START_REQUEST;
	shouldStop = false;
}

void gyroStop () {
	shouldStop = true;
}

/*	calculate ticks for z rotation
 */
static void gyroProcessTicks () {
	const uint8_t shift = 13;
	const uint32_t max = (1 << shift);
	const uint32_t mask = ~(max-1);

	if (zaccum > (int32_t) max) {
		const uint32_t a = abs (zaccum);
		zticks += a >> shift;
		/* mask shift bits */
		zaccum -= a & mask;
	} else if (zaccum < -((int32_t) max)) {
		const uint32_t a = abs (zaccum);
		zticks -= a >> shift;
		zaccum += a & mask;
	}
}

/*	process gyro sensor data, returns true if new data is available
 */
bool gyroProcess () {
	switch (state) {
		case START_REQUEST: {
			/* configuration:
			 * disable power-down-mode, enable z
			 * defaults
			 * high-active, push-pull, drdy on int2
			 * select 2000dps
			 */
			static uint8_t data[] = {0b00001100, 0b0, 0b00001000, 0b00110000};
			const bool ret = twRequest (TWM_WRITE, L3GD20, L3GD20_CTRLREG1, data,
					sizeof (data)/sizeof (*data));
			if (ret) {
				state = STARTING;
			}
			break;
		}

		case STARTING:
			if (shouldWakeup (WAKE_I2C)) {
				disableWakeup (WAKE_I2C);
				state = IDLE;
			}
			break;

		case STOPPING:
			if (shouldWakeup (WAKE_I2C)) {
				disableWakeup (WAKE_I2C);
				state = STOPPED;
			}
			break;

		case READING:
			if (shouldWakeup (WAKE_I2C)) {
				disableWakeup (WAKE_I2C);
				state = IDLE;
				/* the bus might be in use again already */
				//assert (twr.status == TWST_OK);
				/* new data transfered, process it */
				/* poor man's noise filter */
				if (abs (zval) > 64) {
					zaccum += zval;
				}
				gyroProcessTicks ();
				return true;
			}
			break;

		case IDLE:
			if (shouldStop) {
				/* enable power-down mode */
				static uint8_t data[] = {0b00000000};

				if (twRequest (TWM_WRITE, L3GD20, L3GD20_CTRLREG1, data,
						sizeof (data)/sizeof (*data))) {
					state = STOPPING;
				}
			} else if (shouldWakeup (WAKE_GYRO) && twRequest (TWM_READ, L3GD20,
						L3GD20_OUTZ, (uint8_t *) &zval, sizeof (zval))) {
				/* new data available in device buffer and bus is free */
				/* wakeup source is disabled by isr to prevent race condition */
				state = READING;
			}

			break;

		default:
			/* ignore */
			break;
	}

	return false;
}

int32_t gyroGetZAccum () {
	return zaccum;
}

void gyroResetZAccum () {
	zaccum = 0;
}

int16_t gyroGetZRaw () {
	return zval;
}

int16_t gyroGetZTicks () {
	return zticks;
}

void gyroResetZTicks () {
	zticks = 0;
}