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69 lines
1.1 KiB
C
69 lines
1.1 KiB
C
/*
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* fw/accel.c - Acceleration sensor
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*
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* Written 2012 by Werner Almesberger
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* Copyright 2012 Werner Almesberger
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*/
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#include <stddef.h>
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#include <stdbool.h>
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#include <stdint.h>
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#include <avr/io.h>
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#include <avr/interrupt.h>
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#include "io.h"
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#include "accel.h"
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void (*sample)(bool x, uint16_t v) = NULL;
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static bool chan_x;
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static inline void admux(bool x)
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{
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ADMUX =
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1 << REFS0 | /* Vref is AVcc */
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(x ? ADC_X : ADC_Y);
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}
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static inline void adcsra(bool start)
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{
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ADCSRA =
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1 << ADEN | /* enable ADC */
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(start ? 1 << ADSC : 0) |
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1 << ADIE | /* enable ADC interrupts */
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7; /* clkADC = clk/128 -> 62.5 kHz */
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}
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ISR(ADC_vect)
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{
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uint16_t v;
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v = ADC;
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if (sample)
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sample(chan_x, v);
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chan_x = !chan_x;
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admux(chan_x);
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adcsra(1);
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}
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void accel_start(void)
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{
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adcsra(0);
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admux(1);
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chan_x = 1;
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}
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