Commit 6bcdbcde76972191ef8fb247cfcd630cb4ac4de0

  • avatar
  • dcoberii
  • Wed Apr 22 19:03:22 CEST 2009
Added fist round of accelerometer files
Wand/main/accel.c
(80 / 0)
  
1
2#include <avr/io.h>
3#include <avr/interrupt.h>
4#include <inttypes.h>
5#include "fantasia_packets.h"
6#include "accel.h"
7
8#define AVERAGE 16
9
10volatile uint16_t x, y, z;
11
12//volatile static void (*tiggerAccel)();
13
14//ADC sampling complete interrupt
15ISR(ADC_vect){
16
17 //disable interrupts (keeps interrupts from nesting)
18 cli();
19
20 // When we try to change the ADC Channel (by setting ADMUX) the next capture has already started
21 // And so the channel change won't take effect until one cycle later.
22 // When the next ADC_vect is triggered then it will have the value from the old channel but ADMUX
23 // will point to the new channel
24 // Since this code changes the channel on every cycle it means ADMUX is always one step ahead of us
25 // so the reading for y (ADMUX&0x0F==4) is actually the value of x, etc.
26 // That is why the cases do not match
27
28 //Mask the ADC mux to see what channel we just read from (give or take)
29 uint8_t test = (ADMUX&0x0F);
30
31 switch(test){
32 case 4: //X-axis
33 x= ((AVERAGE-1)*x+ADCW)/AVERAGE;
34 ADMUX = 0x45;
35 break;
36 case 5: //Y-axis
37 y= ((AVERAGE-1)*y+ADCW)/AVERAGE;
38 ADMUX = 0x43;
39 break;
40 case 3: //Z-axis
41 z= ((AVERAGE-1)*z+ADCW)/AVERAGE;
42 ADMUX = 0x44;
43 break;
44 }
45
46 //re-enable global interrupts
47 sei();
48
49}
50
51
52//Initilizes all ADC stuff
53//Sets up the trigger function pointer
54void initAccel(){//void(*tiggerFunc)(void)){
55
56 //setup ADC in free running mode (see datasheet)
57 ADMUX = 0x44; // 8b 01 0 x 0100 (aVCC RightAdjust x Channel 4)
58 ADCSRB = 0x0; // 8b x 0 xxx 000 (x ACME xxx FreeRunningMode)
59 ADCSRA = 0xE8; // 8b 1 1 1 x 1 000 (EnableADC Start EnableTrigger x EnableInt clk/2)
60 x=0;
61 y=0;
62 z=0;
63 //tiggerAccel=triggerFunc;
64
65}
66
67
68//returns ADC values (not averaged yet)
69//Called during poll or by timer
70void pollAccel(accel_data_t *data){
71
72 //this is a pirimitive form of mutexing
73 cli();
74 //perform the 45 degree transformation:
75 data->x=(((0xFF-(y>>2))*181)>>8)+(((0xFF-(x>>2))*181)>>8);
76 data->y=(((y>>2)*181)>>8)+(((0xFF-(x>>2))*181)>>8);
77 data->z=0xFF-(z>>2);
78 sei();
79
80}
Wand/main/accel.h
(10 / 0)
  
1
2#ifndef ACCEL_H
3#define ACCEL_H
4
5#include "fantasia_packets.h"
6
7 void initAccel();
8 void pollAccel(accel_data_t *data);
9
10#endif