-
Notifications
You must be signed in to change notification settings - Fork 2
/
Timer_Interrupt_Notes.ino
323 lines (215 loc) · 12.1 KB
/
Timer_Interrupt_Notes.ino
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
/*
These notes put together by Joel Murphy for Pulse Sensor Amped, 2015
The code that this section is attached to uses a timer interrupt
to sample the Pulse Sensor with consistent and regular timing.
The code is setup to read Pulse Sensor signal at 500Hz (every 2mS).
The reasoning for this can be found here:
http://pulsesensor.com/pages/pulse-sensor-amped-arduino-v1dot1
There are issues with using different timers to control the Pulse Sensor sample rate.
Sometimes, user will need to switch timers for access to other code libraries.
Also, some other hardware may have different timer setup requirements. This page
will cover those different needs and reveal the necessary settings. There are two
part of the code that will be discussed. The interruptSetup() routine, and
the interrupt function call. Depending on your needs, or the Arduino variant that you use,
check below for the correct settings.
******************************************************************************************
ARDUINO UNO, Pro 328-5V/16MHZ, Pro-Mini 328-5V/16MHz (or any board with ATmega328P running at 16MHz)
>> Timer2
Pulse Sensor Arduino UNO uses Timer2 by default.
Use of Timer2 interferes with PWM on pins 3 and 11.
There is also a conflict with the Tone library, so if you want tones, use Timer1 below.
void interruptSetup(){
// Initializes Timer2 to throw an interrupt every 2mS.
TCCR2A = 0x02; // DISABLE PWM ON DIGITAL PINS 3 AND 11, AND GO INTO CTC MODE
TCCR2B = 0x06; // DON'T FORCE COMPARE, 256 PRESCALER
OCR2A = 0X7C; // SET THE TOP OF THE COUNT TO 124 FOR 500Hz SAMPLE RATE
TIMSK2 = 0x02; // ENABLE INTERRUPT ON MATCH BETWEEN TIMER2 AND OCR2A
sei(); // MAKE SURE GLOBAL INTERRUPTS ARE ENABLED
}
use the following interrupt vector with Timer2
ISR(TIMER2_COMPA_vect)
>> Timer1
Use of Timer1 interferes with PWM on pins 9 and 10.
The Servo library also uses Timer1, so if you want servos, use Timer2 above.
void interruptSetup(){
// Initializes Timer1 to throw an interrupt every 2mS.
TCCR1A = 0x00; // DISABLE OUTPUTS AND PWM ON DIGITAL PINS 9 & 10
TCCR1B = 0x11; // GO INTO 'PHASE AND FREQUENCY CORRECT' MODE, NO PRESCALER
TCCR1C = 0x00; // DON'T FORCE COMPARE
TIMSK1 = 0x01; // ENABLE OVERFLOW INTERRUPT (TOIE1)
ICR1 = 16000; // TRIGGER TIMER INTERRUPT EVERY 2mS
sei(); // MAKE SURE GLOBAL INTERRUPTS ARE ENABLED
}
Use the following ISR vector for the Timer1 setup above
ISR(TIMER1_OVF_vect)
>> Timer0
DON'T USE TIMER0! Timer0 is used for counting delay(), millis(), and micros().
MESSING WITH Timer0 IS HIGHLY UNADVISED!
******************************************************************************************
ARDUINO Fio, Lilypad, ProMini328-3V/8MHz (or any board with ATmega328P running at 8MHz)
>> Timer2
Pulse Sensor Arduino UNO uses Timer2 by default.
Use of Timer2 interferes with PWM on pins 3 and 11.
There is also a conflict with the Tone library, so if you want tones, use Timer1 below.
void interruptSetup(){
// Initializes Timer2 to throw an interrupt every 2mS.
TCCR2A = 0x02; // DISABLE PWM ON DIGITAL PINS 3 AND 11, AND GO INTO CTC MODE
TCCR2B = 0x05; // DON'T FORCE COMPARE, 128 PRESCALER
OCR2A = 0X7C; // SET THE TOP OF THE COUNT TO 124 FOR 500Hz SAMPLE RATE
TIMSK2 = 0x02; // ENABLE INTERRUPT ON MATCH BETWEEN TIMER2 AND OCR2A
sei(); // MAKE SURE GLOBAL INTERRUPTS ARE ENABLED
}
use the following interrupt vector with Timer2
ISR(TIMER2_COMPA_vect)
>> Timer1
Use of Timer1 interferes with PWM on pins 9 and 10.
The Servo library also uses Timer1, so if you want servos, use Timer2 above.
void interruptSetup(){
// Initializes Timer1 to throw an interrupt every 2mS.
TCCR1A = 0x00; // DISABLE OUTPUTS AND PWM ON DIGITAL PINS 9 & 10
TCCR1B = 0x11; // GO INTO 'PHASE AND FREQUENCY CORRECT' MODE, NO PRESCALER
TCCR1C = 0x00; // DON'T FORCE COMPARE
TIMSK1 = 0x01; // ENABLE OVERFLOW INTERRUPT (TOIE1)
ICR1 = 8000; // TRIGGER TIMER INTERRUPT EVERY 2mS
sei(); // MAKE SURE GLOBAL INTERRUPTS ARE ENABLED
}
Use the following ISR vector for the Timer1 setup above
ISR(TIMER1_OVF_vect)
>> Timer0
DON'T USE TIMER0! Timer0 is used for counting delay(), millis(), and micros().
MESSING WITH Timer0 IS HIGHLY UNADVISED!
******************************************************************************************
ARDUINO Leonardo (or any board with ATmega32u4 running at 16MHz)
>> Timer1
Use of Timer1 interferes with PWM on pins 9 and 10.
void interruptSetup(){
TCCR1A = 0x00;
TCCR1B = 0x0C; // prescaler = 256
OCR1A = 0x7C; // count to 124
TIMSK1 = 0x02;
sei();
}
The only other thing you will need is the correct ISR vector in the next step.
ISR(TIMER1_COMPA_vect)
******************************************************************************************
ADAFRUIT Flora, ARDUINO Fio v3 (or any other board with ATmega32u4 running at 8MHz)
>> Timer1
Use of Timer1 interferes with PWM on pins 9 and 10.
void interruptSetup(){
TCCR1A = 0x00;
TCCR1B = 0x0C; // prescaler = 256
OCR1A = 0x3E; // count to 62
TIMSK1 = 0x02;
sei();
}
The only other thing you will need is the correct ISR vector in the next step.
ISR(TIMER1_COMPA_vect)
******************************************************************************************
ADAFRUIT Gemma, ADAFRUIT Trinket 8MHz, Digispark Pro 8MHz, (or any other board with ATtiny85 running at 8MHz)
NOTE: Gemma does not do serial communication! Comment out or remove the Serial code in the Arduino sketch!
NOTE: You must use Software Serial with the Trinket or Digispark!
A the top of the main code page put these lines
#define rxPin 3
#define txPin 4
SoftwareSerial uart(rxPin, txPin);
Then, whenever the word 'Serial' is used, replace it with 'uart'
example:
change Serial.begin(115200); to uart.begin(57600);
NOTE: Use pin 2 to connect the Pulse Sensor Purple Pin on Trinket and Gemma!
Timer1
Use of Timer1 breaks PWM output on pin D1
void interruptSetup(){
TCCR1 = 0x88; // Clear Timer on Compare, Set Prescaler to 128 TEST VALUE
GTCCR &= 0x81; // Disable PWM, don't connect pins to events
OCR1C = 0x7C; // Set the top of the count to 124 TEST VALUE
OCR1A = 0x7C; // Set the timer to interrupt after counting to TEST VALUE
bitSet(TIMSK,6); // Enable interrupt on match between TCNT1 and OCR1A
sei(); // Enable global interrupts
}
The only other thing you will need is the correct ISR vector in the next step.
ISR(TIMER1_COMPA_vect)
******************************************************************************************
ADAFRUIT Trinket with 16MHz software setting, Digispark Pro 16MHz, (or any other board with ATtiny85 running at 16MHz)
NOTE: Use analog pin 2 for the Pulse Sensor purple wire.
NOTE: You must use Software Serial with the Trinket or Digispark!
A the top of the main code page put these lines
#define rxPin 3
#define txPin 4
SoftwareSerial uart(rxPin, txPin);
Then, whenever the word 'Serial' is used, replace it with 'uart'
example:
change Serial.begin(115200); to uart.begin(57600);
Timer1
Use of Timer1 breaks PWM output on pin D1
void interruptSetup(){
TCCR1 = 0x89; // Clear Timer on Compare, Set Prescaler to 256
GTCCR &= 0x81; // Disable PWM, don't connect pins to events
OCR1C = 0x7C; // Set the top of the count to 124
OCR1A = 0x7C; // Set the timer to interrupt after counting to 124
bitSet(TIMSK,6); // Enable interrupt on match between TCNT1 and OCR1A
sei(); // Enable global interrupts
}
The only other thing you will need is the correct ISR vector in the next step.
ISR(TIMER1_COMPA_vect)
******************************************************************************************
IF YOU DON'T SEE THE MICROCONTROLLER YOU ARE USING, BUT YOU WANT A QUICK AND DIRTY SOLUTION
So many new micros are coming out that it's kind of mind boggling. We will add to this list with
code that uses interupts when we can, but if your micro is not listed here, and you are not willing
or able to grab a hardware timer yourself, here is a shortcut that will work.
It won't have the tight timing of a hardware interrupt, but it just might be good enough.
We are calling this the 'Software Interrupt' version.
The code below will set up a microsecond timer and 'trigger' every 2mS (or so).
FIRST:
You will need to change the name of the funcion in the Interrupts tab from
'ISR(TIMER2_COMPA_vect)'
to
'void getPulse()'
THEN:
Comment out the entire interruptSetup() function in the interrupts tab in order for this to work.
USE:
The code example below. Notice that we are using the micros() and the millis() to time the sample rate and the fade rate.
DO NOT put any delays in the loop, or it will break the sample timing!
Happy Hacking!
// FIRST, CREATE VARIABLES TO PERFORM THE SAMPLE TIMING AND LED FADE FUNCTIONS
unsigned long lastTime; // used to time the Pulse Sensor samples
unsigned long thisTime; // used to time the Pulse Sensor samples
unsigned long fadeTime; // used to time the LED fade
void setup(){
pinMode(blinkPin,OUTPUT); // pin that will blink to your heartbeat!
pinMode(fadePin,OUTPUT); // pin that will fade to your heartbeat!
Serial.begin(115200); // we agree to talk fast!
// ADD THIS LINE IN PLACE OF THE interruptSetup() CALL
lastTime = micros(); // get the time so we can create a software 'interrupt'
// IF YOU ARE POWERING The Pulse Sensor AT VOLTAGE LESS THAN THE BOARD VOLTAGE,
// UN-COMMENT THE NEXT LINE AND APPLY THAT VOLTAGE TO THE A-REF PIN
// analogReference(EXTERNAL);
} //end of setup()
//IN THE LOOP, ADD THE CODE THAT WILL DO THE 2mS TIMING, AND CALL THE getPulse() FUNCTION.
void loop(){
serialOutput() ;
thisTime = micros(); // GET THE CURRENT TIME
if(thisTime - lastTime > 2000){ // CHECK TO SEE IF 2mS HAS PASSED
lastTime = thisTime; // KEEP TRACK FOR NEXT TIME
getPulse(); //CHANGE 'ISR(TIMER2_COMPA_vect)' TO 'getPulse()' IN THE INTERRUPTS TAB!
}
if (QS == true){ // A Heartbeat Was Found
// BPM and IBI have been Determined
// Quantified Self "QS" true when arduino finds a heartbeat
fadeRate = 255; // Makes the LED Fade Effect Happen
// Set 'fadeRate' Variable to 255 to fade LED with pulse
fadeTime = millis(); // Set the fade timer to fade the LED
serialOutputWhenBeatHappens(); // A Beat Happened, Output that to serial.
QS = false; // reset the Quantified Self flag for next time
}
if(millis() - fadeTime > 20){
fadeTime = millis();
ledFadeToBeat(); // Makes the LED Fade Effect Happen
}
} // end of loop
******************************************************************************************
******************************************************************************************
******************************************************************************************
******************************************************************************************
******************************************************************************************
******************************************************************************************
*/