aboutsummaryrefslogtreecommitdiff
path: root/gyro.c
blob: 5b32314f0c7ab189dcb12bf7ef383533deb4d00e (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
#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 STOP_REQUEST 3
#define STOPPING 4
#define READING 5
#define IDLE 6
static uint8_t state = STOPPED;

/* 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;
}

void gyroStop () {
	assert (state == IDLE);
	state = STOP_REQUEST;
}

/*	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 STOP_REQUEST: {
			/* enable power-down mode */
			static uint8_t data[] = {0b00000000};

			const bool ret = twRequest (TWM_WRITE, L3GD20, L3GD20_CTRLREG1, data,
					sizeof (data)/sizeof (*data));
			if (ret) {
				state = STOPPING;
			}
			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 (shouldWakeup (WAKE_GYRO) && twr.status == TWST_OK) {
				/* new data available in device buffer and bus is free */
				const bool ret = twRequest (TWM_READ, L3GD20, L3GD20_OUTZ,
						(uint8_t *) &zval, sizeof (zval));
				assert (ret);
				/* 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;
}