Root/
| 1 | /* |
| 2 | * fw/accel.c - Acceleration sensor |
| 3 | * |
| 4 | * Written 2012 by Werner Almesberger |
| 5 | * Copyright 2012 Werner Almesberger |
| 6 | * |
| 7 | * This program is free software; you can redistribute it and/or modify |
| 8 | * it under the terms of the GNU General Public License as published by |
| 9 | * the Free Software Foundation; either version 2 of the License, or |
| 10 | * (at your option) any later version. |
| 11 | */ |
| 12 | |
| 13 | |
| 14 | #include <stddef.h> |
| 15 | #include <stdbool.h> |
| 16 | #include <stdint.h> |
| 17 | |
| 18 | #include <avr/io.h> |
| 19 | #include <avr/interrupt.h> |
| 20 | #define F_CPU 8000000UL |
| 21 | #include <util/delay.h> |
| 22 | |
| 23 | #include "io.h" |
| 24 | #include "accel.h" |
| 25 | |
| 26 | |
| 27 | void (*sample)(uint16_t x, uint16_t y) = NULL; |
| 28 | |
| 29 | |
| 30 | static bool chan_x; |
| 31 | |
| 32 | |
| 33 | static inline void admux(bool x) |
| 34 | { |
| 35 | ADMUX = |
| 36 | 1 << REFS0 | /* Vref is AVcc */ |
| 37 | (x ? ADC_X : ADC_Y); |
| 38 | } |
| 39 | |
| 40 | |
| 41 | static inline void adcsra(bool start) |
| 42 | { |
| 43 | /* |
| 44 | * The ADC needs to run at clkADC <= 200 kHz for full resolution. |
| 45 | * At clkADC = 125 kHz, a conversion takes about 110 us. |
| 46 | */ |
| 47 | ADCSRA = |
| 48 | 1 << ADEN | /* enable ADC */ |
| 49 | (start ? 1 << ADSC : 0) | |
| 50 | 1 << ADIE | /* enable ADC interrupts */ |
| 51 | 6; /* clkADC = clk/64 -> 125 kHz */ |
| 52 | } |
| 53 | |
| 54 | |
| 55 | uint16_t measure_ref(void) |
| 56 | { |
| 57 | while (ADCSRA & (1 << ADSC)); |
| 58 | adcsra(0); |
| 59 | ADMUX = |
| 60 | 1 << REFS0 | /* Vref is AVcc */ |
| 61 | 14; /* Vbg (1.1 V) */ |
| 62 | _delay_us(100); |
| 63 | adcsra(1); |
| 64 | while (ADCSRA & (1 << ADSC)); |
| 65 | return ADC; |
| 66 | } |
| 67 | |
| 68 | |
| 69 | ISR(ADC_vect) |
| 70 | { |
| 71 | static uint16_t last_x; |
| 72 | uint16_t v; |
| 73 | |
| 74 | v = ADC; |
| 75 | |
| 76 | if (chan_x) { |
| 77 | last_x = v; |
| 78 | chan_x = 0; |
| 79 | admux(0); |
| 80 | adcsra(1); |
| 81 | } else { |
| 82 | sample(last_x, v); |
| 83 | } |
| 84 | } |
| 85 | |
| 86 | |
| 87 | ISR(TIMER0_OVF_vect) |
| 88 | { |
| 89 | chan_x = 1; |
| 90 | admux(1); |
| 91 | adcsra(1); |
| 92 | } |
| 93 | |
| 94 | |
| 95 | void accel_start(void) |
| 96 | { |
| 97 | adcsra(0); |
| 98 | |
| 99 | TCNT0 = 0; |
| 100 | OCR0A = 62; /* 8 MHz/64/62 = 2.02 kHz */ |
| 101 | TCCR0A = |
| 102 | 1 << WGM01 | /* WG Mode 7 (Fast PWM to OCR0A) */ |
| 103 | 1 << WGM00; |
| 104 | TCCR0B = |
| 105 | 1 << WGM02 | /* WG Mode 7, continued */ |
| 106 | 1 << CS01 | /* clkIO/64 */ |
| 107 | 1 << CS00; |
| 108 | TIMSK0 = 1 << TOIE0; /* interrupt on overflow */ |
| 109 | } |
| 110 |
Branches:
master
tornado-v1
