wiring_analog.c
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1 /*
2  wiring_analog.c - analog input and output
3  Part of Arduino - http://www.arduino.cc/
4 
5  Copyright (c) 2005-2006 David A. Mellis
6 
7  This library is free software; you can redistribute it and/or
8  modify it under the terms of the GNU Lesser General Public
9  License as published by the Free Software Foundation; either
10  version 2.1 of the License, or (at your option) any later version.
11 
12  This library is distributed in the hope that it will be useful,
13  but WITHOUT ANY WARRANTY; without even the implied warranty of
14  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15  Lesser General Public License for more details.
16 
17  You should have received a copy of the GNU Lesser General
18  Public License along with this library; if not, write to the
19  Free Software Foundation, Inc., 59 Temple Place, Suite 330,
20  Boston, MA 02111-1307 USA
21 
22  Modified 28 September 2010 by Mark Sproul
23 */
24 
25 #include "wiring_private.h"
26 #include "pins_arduino.h"
27 
28 uint8_t analog_reference = DEFAULT;
29 
30 void analogReference(uint8_t mode)
31 {
32  // can't actually set the register here because the default setting
33  // will connect AVCC and the AREF pin, which would cause a short if
34  // there's something connected to AREF.
35  analog_reference = mode;
36 }
37 
38 int analogRead(uint8_t pin)
39 {
40  uint8_t low, high;
41 
42 #if defined(analogPinToChannel)
43 #if defined(__AVR_ATmega32U4__)
44  if (pin >= 18) pin -= 18; // allow for channel or pin numbers
45 #endif
46  pin = analogPinToChannel(pin);
47 #elif defined(__AVR_ATmega1280__) || defined(__AVR_ATmega2560__)
48  if (pin >= 54) pin -= 54; // allow for channel or pin numbers
49 #elif defined(__AVR_ATmega32U4__)
50  if (pin >= 18) pin -= 18; // allow for channel or pin numbers
51 #elif defined(__AVR_ATmega1284__) || defined(__AVR_ATmega1284P__) || defined(__AVR_ATmega644__) || defined(__AVR_ATmega644A__) || defined(__AVR_ATmega644P__) || defined(__AVR_ATmega644PA__)
52  if (pin >= 24) pin -= 24; // allow for channel or pin numbers
53 #else
54  if (pin >= 14) pin -= 14; // allow for channel or pin numbers
55 #endif
56 
57 #if defined(ADCSRB) && defined(MUX5)
58  // the MUX5 bit of ADCSRB selects whether we're reading from channels
59  // 0 to 7 (MUX5 low) or 8 to 15 (MUX5 high).
60  ADCSRB = (ADCSRB & ~(1 << MUX5)) | (((pin >> 3) & 0x01) << MUX5);
61 #endif
62 
63  // set the analog reference (high two bits of ADMUX) and select the
64  // channel (low 4 bits). this also sets ADLAR (left-adjust result)
65  // to 0 (the default).
66 #if defined(ADMUX)
67 #if defined(__AVR_ATtiny25__) || defined(__AVR_ATtiny45__) || defined(__AVR_ATtiny85__)
68  ADMUX = (analog_reference << 4) | (pin & 0x07);
69 #else
70  ADMUX = (analog_reference << 6) | (pin & 0x07);
71 #endif
72 #endif
73 
74  // without a delay, we seem to read from the wrong channel
75  //delay(1);
76 
77 #if defined(ADCSRA) && defined(ADCL)
78  // start the conversion
79  sbi(ADCSRA, ADSC);
80 
81  // ADSC is cleared when the conversion finishes
82  while (bit_is_set(ADCSRA, ADSC));
83 
84  // we have to read ADCL first; doing so locks both ADCL
85  // and ADCH until ADCH is read. reading ADCL second would
86  // cause the results of each conversion to be discarded,
87  // as ADCL and ADCH would be locked when it completed.
88  low = ADCL;
89  high = ADCH;
90 #else
91  // we dont have an ADC, return 0
92  low = 0;
93  high = 0;
94 #endif
95 
96  // combine the two bytes
97  return (high << 8) | low;
98 }
99 
100 // Right now, PWM output only works on the pins with
101 // hardware support. These are defined in the appropriate
102 // pins_*.c file. For the rest of the pins, we default
103 // to digital output.
104 void analogWrite(uint8_t pin, int val)
105 {
106  // We need to make sure the PWM output is enabled for those pins
107  // that support it, as we turn it off when digitally reading or
108  // writing with them. Also, make sure the pin is in output mode
109  // for consistenty with Wiring, which doesn't require a pinMode
110  // call for the analog output pins.
111  pinMode(pin, OUTPUT);
112  if (val == 0)
113  {
114  digitalWrite(pin, LOW);
115  }
116  else if (val == 255)
117  {
118  digitalWrite(pin, HIGH);
119  }
120  else
121  {
122  switch(digitalPinToTimer(pin))
123  {
124  // XXX fix needed for atmega8
125  #if defined(TCCR0) && defined(COM00) && !defined(__AVR_ATmega8__)
126  case TIMER0A:
127  // connect pwm to pin on timer 0
128  sbi(TCCR0, COM00);
129  OCR0 = val; // set pwm duty
130  break;
131  #endif
132 
133  #if defined(TCCR0A) && defined(COM0A1)
134  case TIMER0A:
135  // connect pwm to pin on timer 0, channel A
136  sbi(TCCR0A, COM0A1);
137  OCR0A = val; // set pwm duty
138  break;
139  #endif
140 
141  #if defined(TCCR0A) && defined(COM0B1)
142  case TIMER0B:
143  // connect pwm to pin on timer 0, channel B
144  sbi(TCCR0A, COM0B1);
145  OCR0B = val; // set pwm duty
146  break;
147  #endif
148 
149  #if defined(TCCR1A) && defined(COM1A1)
150  case TIMER1A:
151  // connect pwm to pin on timer 1, channel A
152  sbi(TCCR1A, COM1A1);
153  OCR1A = val; // set pwm duty
154  break;
155  #endif
156 
157  #if defined(TCCR1A) && defined(COM1B1)
158  case TIMER1B:
159  // connect pwm to pin on timer 1, channel B
160  sbi(TCCR1A, COM1B1);
161  OCR1B = val; // set pwm duty
162  break;
163  #endif
164 
165  #if defined(TCCR1A) && defined(COM1C1)
166  case TIMER1C:
167  // connect pwm to pin on timer 1, channel B
168  sbi(TCCR1A, COM1C1);
169  OCR1C = val; // set pwm duty
170  break;
171  #endif
172 
173  #if defined(TCCR2) && defined(COM21)
174  case TIMER2:
175  // connect pwm to pin on timer 2
176  sbi(TCCR2, COM21);
177  OCR2 = val; // set pwm duty
178  break;
179  #endif
180 
181  #if defined(TCCR2A) && defined(COM2A1)
182  case TIMER2A:
183  // connect pwm to pin on timer 2, channel A
184  sbi(TCCR2A, COM2A1);
185  OCR2A = val; // set pwm duty
186  break;
187  #endif
188 
189  #if defined(TCCR2A) && defined(COM2B1)
190  case TIMER2B:
191  // connect pwm to pin on timer 2, channel B
192  sbi(TCCR2A, COM2B1);
193  OCR2B = val; // set pwm duty
194  break;
195  #endif
196 
197  #if defined(TCCR3A) && defined(COM3A1)
198  case TIMER3A:
199  // connect pwm to pin on timer 3, channel A
200  sbi(TCCR3A, COM3A1);
201  OCR3A = val; // set pwm duty
202  break;
203  #endif
204 
205  #if defined(TCCR3A) && defined(COM3B1)
206  case TIMER3B:
207  // connect pwm to pin on timer 3, channel B
208  sbi(TCCR3A, COM3B1);
209  OCR3B = val; // set pwm duty
210  break;
211  #endif
212 
213  #if defined(TCCR3A) && defined(COM3C1)
214  case TIMER3C:
215  // connect pwm to pin on timer 3, channel C
216  sbi(TCCR3A, COM3C1);
217  OCR3C = val; // set pwm duty
218  break;
219  #endif
220 
221  #if defined(TCCR4A)
222  case TIMER4A:
223  //connect pwm to pin on timer 4, channel A
224  sbi(TCCR4A, COM4A1);
225  #if defined(COM4A0) // only used on 32U4
226  cbi(TCCR4A, COM4A0);
227  #endif
228  OCR4A = val; // set pwm duty
229  break;
230  #endif
231 
232  #if defined(TCCR4A) && defined(COM4B1)
233  case TIMER4B:
234  // connect pwm to pin on timer 4, channel B
235  sbi(TCCR4A, COM4B1);
236  OCR4B = val; // set pwm duty
237  break;
238  #endif
239 
240  #if defined(TCCR4A) && defined(COM4C1)
241  case TIMER4C:
242  // connect pwm to pin on timer 4, channel C
243  sbi(TCCR4A, COM4C1);
244  OCR4C = val; // set pwm duty
245  break;
246  #endif
247 
248  #if defined(TCCR4C) && defined(COM4D1)
249  case TIMER4D:
250  // connect pwm to pin on timer 4, channel D
251  sbi(TCCR4C, COM4D1);
252  #if defined(COM4D0) // only used on 32U4
253  cbi(TCCR4C, COM4D0);
254  #endif
255  OCR4D = val; // set pwm duty
256  break;
257  #endif
258 
259 
260  #if defined(TCCR5A) && defined(COM5A1)
261  case TIMER5A:
262  // connect pwm to pin on timer 5, channel A
263  sbi(TCCR5A, COM5A1);
264  OCR5A = val; // set pwm duty
265  break;
266  #endif
267 
268  #if defined(TCCR5A) && defined(COM5B1)
269  case TIMER5B:
270  // connect pwm to pin on timer 5, channel B
271  sbi(TCCR5A, COM5B1);
272  OCR5B = val; // set pwm duty
273  break;
274  #endif
275 
276  #if defined(TCCR5A) && defined(COM5C1)
277  case TIMER5C:
278  // connect pwm to pin on timer 5, channel C
279  sbi(TCCR5A, COM5C1);
280  OCR5C = val; // set pwm duty
281  break;
282  #endif
283 
284  case NOT_ON_TIMER:
285  default:
286  if (val < 128) {
287  digitalWrite(pin, LOW);
288  } else {
289  digitalWrite(pin, HIGH);
290  }
291  }
292  }
293 }
294 
TIMER0A
#define TIMER0A
Definition: Arduino.h:205
pinMode
void pinMode(uint8_t, uint8_t)
Definition: wiring_digital.c:29
TIMER4B
#define TIMER4B
Definition: Arduino.h:218
analogWrite
void analogWrite(uint8_t pin, int val)
Definition: wiring_analog.c:104
TIMER4C
#define TIMER4C
Definition: Arduino.h:219
analogReference
void analogReference(uint8_t mode)
Definition: wiring_analog.c:30
TIMER1C
#define TIMER1C
Definition: Arduino.h:209
analog_reference
uint8_t analog_reference
Definition: wiring_analog.c:28
mode
GLenum mode
TIMER4A
#define TIMER4A
Definition: Arduino.h:217
NOT_ON_TIMER
#define NOT_ON_TIMER
Definition: Arduino.h:204
TIMER1B
#define TIMER1B
Definition: Arduino.h:208
OUTPUT
#define OUTPUT
Definition: Arduino.h:44
wiring_private.h
HIGH
#define HIGH
Definition: Arduino.h:40
digitalPinToTimer
#define digitalPinToTimer(P)
Definition: Arduino.h:179
TIMER3A
#define TIMER3A
Definition: Arduino.h:214
cbi
#define cbi(sfr, bit)
Definition: wiring_private.h:38
TIMER5A
#define TIMER5A
Definition: Arduino.h:221
TIMER5C
#define TIMER5C
Definition: Arduino.h:223
TIMER2B
#define TIMER2B
Definition: Arduino.h:212
TIMER1A
#define TIMER1A
Definition: Arduino.h:207
TIMER3B
#define TIMER3B
Definition: Arduino.h:215
TIMER3C
#define TIMER3C
Definition: Arduino.h:216
TIMER2A
#define TIMER2A
Definition: Arduino.h:211
digitalWrite
void digitalWrite(uint8_t, uint8_t)
Definition: wiring_digital.c:138
DEFAULT
#define DEFAULT
Definition: Arduino.h:83
TIMER2
#define TIMER2
Definition: Arduino.h:210
TIMER5B
#define TIMER5B
Definition: Arduino.h:222
LOW
#define LOW
Definition: Arduino.h:41
val
GLuint GLfloat * val
TIMER0B
#define TIMER0B
Definition: Arduino.h:206
analogRead
int analogRead(uint8_t pin)
Definition: wiring_analog.c:38
TIMER4D
#define TIMER4D
Definition: Arduino.h:220
sbi
#define sbi(sfr, bit)
Definition: wiring_private.h:41

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