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