root / toolbox / current.c @ 975af07c
History | View | Annotate | Download (1.95 KB)
1 | 10936c07 | Tom Mullins | #include "current.h" |
---|---|---|---|
2 | #include <avr/io.h> |
||
3 | cbda92cc | Tom Mullins | #include <avr/interrupt.h> |
4 | #include <math.h> |
||
5 | |||
6 | #define CYCLES_PER_SECOND 60 // wall power |
||
7 | 975af07c | Tom Mullins | #define SAMPLES_PER_CYCLE 16 |
8 | #define N_SAMPLES 48 |
||
9 | cbda92cc | Tom Mullins | |
10 | unsigned int samples[N_SAMPLES]; |
||
11 | int sample_idx;
|
||
12 | |||
13 | unsigned int sum; |
||
14 | unsigned long sum_sq; |
||
15 | 10936c07 | Tom Mullins | |
16 | void current_init() {
|
||
17 | cbda92cc | Tom Mullins | |
18 | f4df665c | Tom Mullins | /* TODO reduce power consumption with DIDR* */
|
19 | cbda92cc | Tom Mullins | |
20 | /*
|
||
21 | f4df665c | Tom Mullins | * COM1A = COM1B = 0, disconnect pins
|
22 | * WGM1 = 4, clear timer on compare A
|
||
23 | * CS1 = 5, 1024 prescaler
|
||
24 | cbda92cc | Tom Mullins | */
|
25 | f4df665c | Tom Mullins | TCCR1B |= _BV(WGM12) | _BV(CS12) | _BV(CS10); |
26 | cbda92cc | Tom Mullins | |
27 | f4df665c | Tom Mullins | /* Timer is cleared on A, ADC is triggered on B */
|
28 | OCR1A = F_CPU / 1024 / SAMPLES_PER_CYCLE / CYCLES_PER_SECOND;
|
||
29 | OCR1B = 0;
|
||
30 | cbda92cc | Tom Mullins | |
31 | 10936c07 | Tom Mullins | /*
|
32 | * REFS = 0, Vcc reference (set to 2 for internal 1.1V reference)
|
||
33 | * MUX = 8, PB3(ADC8)
|
||
34 | */
|
||
35 | ADMUX = _BV(MUX3); |
||
36 | cbda92cc | Tom Mullins | |
37 | 10936c07 | Tom Mullins | /*
|
38 | * ADLAR = 0, right adjust result
|
||
39 | f4df665c | Tom Mullins | * ADTS = 5, start on timer 1 compare match B
|
40 | 10936c07 | Tom Mullins | */
|
41 | f4df665c | Tom Mullins | ADCSRB = _BV(ADTS2) | _BV(ADTS0); |
42 | cbda92cc | Tom Mullins | |
43 | 10936c07 | Tom Mullins | /*
|
44 | * ADEN = 1, enable
|
||
45 | cbda92cc | Tom Mullins | * ADSC = 0, don't start yet
|
46 | 10936c07 | Tom Mullins | * ADATE = 1, auto trigger
|
47 | cbda92cc | Tom Mullins | * ADIE = 1, enable interrupt
|
48 | * ADPS = 4, prescale clock by 16
|
||
49 | 10936c07 | Tom Mullins | */
|
50 | cbda92cc | Tom Mullins | ADCSRA |= _BV(ADEN) | _BV(ADATE) | _BV(ADIE) | _BV(ADPS2); |
51 | 10936c07 | Tom Mullins | } |
52 | |||
53 | cbda92cc | Tom Mullins | ISR(ADC_vect) { |
54 | unsigned int old, new; |
||
55 | |||
56 | new = ADC; |
||
57 | |||
58 | /* put sample into ring buffer */
|
||
59 | old = samples[sample_idx]; |
||
60 | samples[sample_idx++] = new; |
||
61 | if (sample_idx == N_SAMPLES)
|
||
62 | sample_idx = 0;
|
||
63 | |||
64 | /* keep a running total of samples and samples squared */
|
||
65 | sum += new; |
||
66 | sum -= old; |
||
67 | sum_sq += new*new; |
||
68 | sum_sq -= old*old; |
||
69 | } |
||
70 | |||
71 | /*unsigned char isqrt(unsigned int x) {
|
||
72 | unsigned int sqrt, mulmask;
|
||
73 | sqrt = 0;
|
||
74 | mulmask = 0x80;
|
||
75 | if (x > 0) {
|
||
76 | while (mulmask) {
|
||
77 | sqrt |= mulmask;
|
||
78 | if (sqrt * sqrt > x)
|
||
79 | sqrt &= ~mulmask;
|
||
80 | mulmask >>= 1;
|
||
81 | }
|
||
82 | }
|
||
83 | return sqrt;
|
||
84 | }*/
|
||
85 | |||
86 | unsigned int current_read() { |
||
87 | unsigned int _sum; |
||
88 | unsigned long _sum_sq; |
||
89 | |||
90 | cli(); |
||
91 | _sum = sum; |
||
92 | _sum_sq = sum_sq; |
||
93 | sei(); |
||
94 | |||
95 | /* calculate the variance using sum and sum_sq */
|
||
96 | 975af07c | Tom Mullins | return (N_SAMPLES*_sum_sq - (unsigned long)_sum*_sum) / |
97 | (N_SAMPLES*(N_SAMPLES-1));
|
||
98 | 10936c07 | Tom Mullins | } |