mirror of
git://projects.qi-hardware.com/antorcha.git
synced 2024-11-01 11:15:55 +02:00
92 lines
1.5 KiB
C
92 lines
1.5 KiB
C
/*
|
|
* fw/accel.c - Acceleration sensor
|
|
*
|
|
* Written 2012 by Werner Almesberger
|
|
* Copyright 2012 Werner Almesberger
|
|
*
|
|
* This program is free software; you can redistribute it and/or modify
|
|
* it under the terms of the GNU General Public License as published by
|
|
* the Free Software Foundation; either version 2 of the License, or
|
|
* (at your option) any later version.
|
|
*/
|
|
|
|
|
|
#include <stddef.h>
|
|
#include <stdbool.h>
|
|
#include <stdint.h>
|
|
|
|
#include <avr/io.h>
|
|
#include <avr/interrupt.h>
|
|
|
|
#include "io.h"
|
|
#include "accel.h"
|
|
|
|
|
|
void (*sample)(bool x, uint16_t v) = NULL;
|
|
|
|
|
|
static bool chan_x;
|
|
|
|
|
|
static inline void admux(bool x)
|
|
{
|
|
ADMUX =
|
|
1 << REFS0 | /* Vref is AVcc */
|
|
(x ? ADC_X : ADC_Y);
|
|
}
|
|
|
|
|
|
static inline void adcsra(bool start)
|
|
{
|
|
/*
|
|
* The ADC needs to run at clkADC <= 200 kHz for full resolution.
|
|
* At clkADC = 125 kHz, a conversion takes about 110 us.
|
|
*/
|
|
ADCSRA =
|
|
1 << ADEN | /* enable ADC */
|
|
(start ? 1 << ADSC : 0) |
|
|
1 << ADIE | /* enable ADC interrupts */
|
|
6; /* clkADC = clk/64 -> 126 kHz */
|
|
}
|
|
|
|
|
|
ISR(ADC_vect)
|
|
{
|
|
uint16_t v;
|
|
|
|
v = ADC;
|
|
if (sample)
|
|
sample(chan_x, v);
|
|
|
|
if (chan_x) {
|
|
chan_x = 0;
|
|
admux(0);
|
|
adcsra(1);
|
|
}
|
|
}
|
|
|
|
|
|
ISR(TIMER0_OVF_vect)
|
|
{
|
|
chan_x = 1;
|
|
admux(1);
|
|
adcsra(1);
|
|
}
|
|
|
|
|
|
void accel_start(void)
|
|
{
|
|
adcsra(0);
|
|
|
|
TCNT0 = 0;
|
|
OCR0A = 125; /* 8 MHz/64/125 = 1 kHz */
|
|
TCCR0A =
|
|
1 << WGM01 | /* WG Mode 7 (Fast PWM to OCR0A) */
|
|
1 << WGM00;
|
|
TCCR0B =
|
|
1 << WGM02 | /* WG Mode 7, continued */
|
|
1 << CS01 | /* clkIO/64 */
|
|
1 << CS00;
|
|
TIMSK0 = 1 << TOIE0; /* interrupt on overflow */
|
|
}
|