mirror of
git://projects.qi-hardware.com/antorcha.git
synced 2024-11-01 11:28:26 +02:00
206eb4d591
A number of changes: - don't enable interrupts, since they often cause hangs (not sure why) - remove GND measurement - wait 100 us between AMUX setup and start of conversion, to let input settle - reduce delay between line setup and samping from 100 ms to 50 ms, for this is already sufficient
108 lines
1.8 KiB
C
108 lines
1.8 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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#define F_CPU 8000000UL
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#include <util/delay.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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/*
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* The ADC needs to run at clkADC <= 200 kHz for full resolution.
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* At clkADC = 125 kHz, a conversion takes about 110 us.
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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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6; /* clkADC = clk/64 -> 126 kHz */
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}
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uint16_t measure_ref(void)
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{
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while (ADCSRA & (1 << ADSC));
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adcsra(0);
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ADMUX =
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1 << REFS0 | /* Vref is AVcc */
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14; /* Vbg (1.1 V) */
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_delay_us(100);
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adcsra(1);
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while (ADCSRA & (1 << ADSC));
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return ADC;
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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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if (chan_x) {
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chan_x = 0;
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admux(0);
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adcsra(1);
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}
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}
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ISR(TIMER0_OVF_vect)
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{
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chan_x = 1;
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admux(1);
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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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TCNT0 = 0;
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OCR0A = 125; /* 8 MHz/64/125 = 1 kHz */
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TCCR0A =
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1 << WGM01 | /* WG Mode 7 (Fast PWM to OCR0A) */
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1 << WGM00;
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TCCR0B =
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1 << WGM02 | /* WG Mode 7, continued */
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1 << CS01 | /* clkIO/64 */
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1 << CS00;
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TIMSK0 = 1 << TOIE0; /* interrupt on overflow */
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}
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