root / toolbox / current.c @ master
History | View | Annotate | Download (1.54 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 | e2a3c71f | Tom Mullins | // TODO the ADC is run once every 2ms no matter what these numbers
|
7 | // say. They're not used. Actual samples/cycle is around 8.3
|
||
8 | cbda92cc | Tom Mullins | #define CYCLES_PER_SECOND 60 // wall power |
9 | e2a3c71f | Tom Mullins | #define SAMPLES_PER_CYCLE 8 |
10 | #define N_SAMPLES 24 |
||
11 | cbda92cc | Tom Mullins | |
12 | unsigned int samples[N_SAMPLES]; |
||
13 | int sample_idx;
|
||
14 | |||
15 | unsigned int sum; |
||
16 | unsigned long sum_sq; |
||
17 | 10936c07 | Tom Mullins | |
18 | void current_init() {
|
||
19 | cbda92cc | Tom Mullins | |
20 | f4df665c | Tom Mullins | /* TODO reduce power consumption with DIDR* */
|
21 | cbda92cc | Tom Mullins | |
22 | /*
|
||
23 | 10936c07 | Tom Mullins | * REFS = 0, Vcc reference (set to 2 for internal 1.1V reference)
|
24 | * MUX = 8, PB3(ADC8)
|
||
25 | */
|
||
26 | ADMUX = _BV(MUX3); |
||
27 | cbda92cc | Tom Mullins | |
28 | 10936c07 | Tom Mullins | /*
|
29 | * ADLAR = 0, right adjust result
|
||
30 | */
|
||
31 | e2a3c71f | Tom Mullins | ADCSRB = 0;
|
32 | cbda92cc | Tom Mullins | |
33 | 10936c07 | Tom Mullins | /*
|
34 | * ADEN = 1, enable
|
||
35 | cbda92cc | Tom Mullins | * ADSC = 0, don't start yet
|
36 | e2a3c71f | Tom Mullins | * ADATE = 0, no auto trigger
|
37 | cbda92cc | Tom Mullins | * ADIE = 1, enable interrupt
|
38 | db11713d | Tom Mullins | * ADPS = 6, prescale clock by 64
|
39 | 10936c07 | Tom Mullins | */
|
40 | e2a3c71f | Tom Mullins | ADCSRA = _BV(ADEN) | _BV(ADIE) | _BV(ADPS2) | _BV(ADPS1); |
41 | } |
||
42 | |||
43 | void current_start_adc() {
|
||
44 | ADCSRA |= _BV(ADSC); |
||
45 | 10936c07 | Tom Mullins | } |
46 | |||
47 | cbda92cc | Tom Mullins | ISR(ADC_vect) { |
48 | unsigned int old, new; |
||
49 | |||
50 | new = ADC; |
||
51 | |||
52 | /* put sample into ring buffer */
|
||
53 | old = samples[sample_idx]; |
||
54 | samples[sample_idx++] = new; |
||
55 | if (sample_idx == N_SAMPLES)
|
||
56 | sample_idx = 0;
|
||
57 | |||
58 | /* keep a running total of samples and samples squared */
|
||
59 | sum += new; |
||
60 | sum -= old; |
||
61 | e8960789 | Tom Mullins | sum_sq += (unsigned long)new*new; |
62 | sum_sq -= (unsigned long)old*old; |
||
63 | cbda92cc | Tom Mullins | } |
64 | |||
65 | unsigned int current_read() { |
||
66 | unsigned int _sum; |
||
67 | unsigned long _sum_sq; |
||
68 | |||
69 | cli(); |
||
70 | _sum = sum; |
||
71 | _sum_sq = sum_sq; |
||
72 | sei(); |
||
73 | |||
74 | /* calculate the variance using sum and sum_sq */
|
||
75 | 975af07c | Tom Mullins | return (N_SAMPLES*_sum_sq - (unsigned long)_sum*_sum) / |
76 | (N_SAMPLES*(N_SAMPLES-1));
|
||
77 | 10936c07 | Tom Mullins | } |