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Many people have had trouble with getting 1-Wire devices to work with the Galileo and Galileo Gen2 boards.
The main reason is that the Galileo and Galileo Gen2 uses IO expanders for many of its GPios. Even with the pins Arduno header pins that have native SoC IO speeds, it is not possible because the GPIOs that control the muxing of those pins uses pins from the IO expanders.
Galileo Muxing For Pin2
Galileo Cypress IO Expander
If we look at the two images taken form the Galileo schematic, IO which is connected to the Arduino Digital 2 pin, is controlled by a mux pin IO2_MUX. This pin is then connected to the Cypress IO expander.
The end result is there is significant latency when switching pin direction using pinMode() becuase it requires I2C transactions with the IO expanders.
I will show a way to use 1-Wire device with the Galileo and Galileo Gen2 boards.
The trick is to use 2 pins instead of 1. For the Galileo, pins 2 and 3 must be used since they are the only pins fast enough to achieve this. For the Galileo Gen2, any pins except pins 7 and 8 can be used.
For this tutorial, I will use a DHT11 sensor which a very cheap and popular 1-Wire humidity and temperature sensor.
The Proper Way
The proper way of doing this is to use a tri-state buffer.
This works because, when pin 3 is pulled HIGH, the tri-state buffer prevents the HIGH signal from being passed to the other side. However, the 1-Wire device still sees a high signal because of the pull-up resistor.
When pin 3 is pulled LOW, the signal passes through the tri-state buffer and a LOW signal is detected by the 1-Wire device.
The Easy Way
For the easy way the only extra hardware needed is a diode such as the 1N4148 signal diode. This essential works the same way as the tri-state buffer method where only a LOW signal passes through because current only passes in one direction through a diode.
Since we are now using two pins, we will also need to make changes in the libraries used. As an example, I modified the DHT-11 library from Adafruit.
1 #ifndef DHT_H
2 #define DHT_H
3 #if ARDUINO >= 100
4 #include "Arduino.h"
5 #else
6 #include "WProgram.h"
7 #endif
8
9 /* DHT library
10
11 MIT license
12 written by Adafruit Industries
13
14 Modified by Dino Tinitigan ([email protected] to work on Intel Galileo boards
15 */
16
17 // how many timing transitions we need to keep track of. 2 * number bits + extra
18 #define MAXTIMINGS 85
19
20 #define DHT11 11
21 #define DHT22 22
22 #define DHT21 21
23 #define AM2301 21
24
25 class DHT {
26 private:
27 uint8_t data[6];
28 uint8_t _inpin, _outpin, _type, _count;
29 unsigned long _lastreadtime;
30 boolean firstreading;
31 int pulseLength(int pin);
32 void delayMicrosGal(unsigned long usec);
33 int bitsToByte(int bits[]);
34
35 public:
36 DHT(uint8_t inPin, uint8_t outPin,uint8_t type, uint8_t count=6);
37 void begin(void);
38 float readTemperature(bool S=false);
39 float convertCtoF(float);
40 float computeHeatIndex(float tempFahrenheit, float percentHumidity);
41 float readHumidity(void);
42 boolean read(void);
43
44
45 };
46 #endif
1 /* DHT library
2
3 MIT license
4 written by Adafruit Industries
5
6 Modified by Dino Tinitigan ([email protected] to work on Intel Galileo boards
7 */
8
9
10 #include "DHT.h"
11
12 DHT::DHT(uint8_t inPin, uint8_t outPin, uint8_t type, uint8_t count) {
13 _inpin = inPin;
14 _outpin = outPin;
15 _type = type;
16 _count = count;
17 firstreading = true;
18 }
19
20 void DHT::begin(void) {
21 // set up the pins!
22 pinMode(_inpin, INPUT);
23 pinMode(_outpin, INPUT);
24 digitalWrite(_outpin, HIGH);
25 _lastreadtime = 0;
26 }
27
28 //boolean S == Scale. True == Farenheit; False == Celcius
29 float DHT::readTemperature(bool S) {
30 float f;
31
32 if (read()) {
33 switch (_type) {
34 case DHT11:
35 f = data[2];
36 if(S)
37 f = convertCtoF(f);
38
39 return f;
40 case DHT22:
41 case DHT21:
42 f = data[2] & 0x7F;
43 f *= 256;
44 f += data[3];
45 f /= 10;
46 if (data[2] & 0x80)
47 f *= -1;
48 if(S)
49 f = convertCtoF(f);
50
51 return f;
52 }
53 }
54 return NAN;
55 }
56
57 float DHT::convertCtoF(float c) {
58 return c * 9 / 5 + 32;
59 }
60
61 float DHT::readHumidity(void) {
62 float f;
63 if (read()) {
64 switch (_type) {
65 case DHT11:
66 f = data[0];
67 return f;
68 case DHT22:
69 case DHT21:
70 f = data[0];
71 f *= 256;
72 f += data[1];
73 f /= 10;
74 return f;
75 }
76 }
77 return NAN;
78 }
79
80 float DHT::computeHeatIndex(float tempFahrenheit, float percentHumidity) {
81 // Adapted from equation at: https://github.com/adafruit/DHT-sensor-library/issues/9 and
82 // Wikipedia: http://en.wikipedia.org/wiki/Heat_index
83 return -42.379 +
84 2.04901523 * tempFahrenheit +
85 10.14333127 * percentHumidity +
86 -0.22475541 * tempFahrenheit*percentHumidity +
87 -0.00683783 * pow(tempFahrenheit, 2) +
88 -0.05481717 * pow(percentHumidity, 2) +
89 0.00122874 * pow(tempFahrenheit, 2) * percentHumidity +
90 0.00085282 * tempFahrenheit*pow(percentHumidity, 2) +
91 -0.00000199 * pow(tempFahrenheit, 2) * pow(percentHumidity, 2);
92 }
93
94
95 boolean DHT::read(void) {
96 uint8_t laststate = HIGH;
97 uint8_t counter = 0;
98 uint8_t j = 0, i;
99 unsigned long currenttime;
100
101 int bitContainer[8];
102
103 // Check if sensor was read less than two seconds ago and return early
104 // to use last reading.
105 currenttime = millis();
106 if (currenttime < _lastreadtime) {
107 // ie there was a rollover
108 _lastreadtime = 0;
109 }
110 if (!firstreading && ((currenttime - _lastreadtime) < 2000)) {
111 return true; // return last correct measurement
112 //delay(2000 - (currenttime - _lastreadtime));
113 }
114 firstreading = false;
115 /*
116 Serial.print("Currtime: "); Serial.print(currenttime);
117 Serial.print(" Lasttime: "); Serial.print(_lastreadtime);
118 */
119 _lastreadtime = millis();
120
121 data[0] = data[1] = data[2] = data[3] = data[4] = 0;
122
123 // pull the pin high and wait 250 milliseconds
124 pinMode(_outpin, OUTPUT_FAST);
125 pinMode(_inpin, INPUT_FAST);
126 digitalWrite(_outpin, HIGH);
127 delay(250);
128
129 // now pull it low for ~20 milliseconds
130 noInterrupts();
131 digitalWrite(_outpin, LOW);
132 delay(20);
133 digitalWrite(_outpin, HIGH);
134 delayMicrosGal(40);
135
136 //read the 40 bits
137 delayMicrosGal(160);
138 for(int bytes = 0; bytes < 5; bytes++)
139 {
140 for(int i = 0; i < 8; i++)
141 {
142 int pulse = pulseLength(_inpin);
143 if(pulse > 30)
144 {
145 bitContainer[i] = 1;
146 }
147 else
148 {
149 bitContainer[i] = 0;
150 }
151 }
152 data[bytes] = bitsToByte(bitContainer);
153 }
154
155 interrupts();
156
157
158 //Serial.println(j, DEC);
159 /**
160 Serial.print(data[0], HEX); Serial.print(", ");
161 Serial.print(data[1], HEX); Serial.print(", ");
162 Serial.print(data[2], HEX); Serial.print(", ");
163 Serial.print(data[3], HEX); Serial.print(", ");
164 Serial.print(data[4], HEX); Serial.print(" =? ");
165 Serial.println(data[0] + data[1] + data[2] + data[3], HEX);
166 **/
167 /**
168 Serial.println(data[0]);
169 Serial.println(data[1]);
170 Serial.println(data[2]);
171 Serial.println(data[3]);
172 Serial.println(data[4]);
173 **/
174 // check we read 40 bits and that the checksum matches
175
176 if((data[4] == ((data[0] + data[1] + data[2] + data[3]) & 0xFF)))
177 {
178 return true;
179 }
180
181
182 return false;
183
184 }
185
186 void DHT::delayMicrosGal(unsigned long usec)
187 {
188 unsigned long a = micros();
189 unsigned long b = a;
190 while((b-a) < usec)
191 {
192 b = micros();
193 }
194 }
195
196 int DHT::pulseLength(int pin)
197 {
198 unsigned long a = micros();
199 unsigned long b = a;
200 unsigned long c = a;
201 int timeout = 150;
202 int fastPin = 0;
203 int highValue = 0;
204
205 if(PLATFORM_NAME == "GalileoGen2")
206 {
207 switch(pin)
208 {
209 case 0:
210 fastPin = GPIO_FAST_ID_QUARK_SC(0x08);
211 highValue = 0x08;
212 break;
213 case 1:
214 fastPin = GPIO_FAST_ID_QUARK_SC(0x10);
215 highValue = 0x10;
216 break;
217 case 2:
218 fastPin = GPIO_FAST_ID_QUARK_SC(0x20);
219 highValue = 0x20;
220 break;
221 case 3:
222 fastPin = GPIO_FAST_ID_QUARK_SC(0x40);
223 highValue = 0x40;
224 break;
225 case 4:
226 fastPin = GPIO_FAST_ID_QUARK_NC_RW(0x10);
227 highValue = 0x10;
228 break;
229 case 5:
230 fastPin = GPIO_FAST_ID_QUARK_NC_CW(0x01);
231 highValue = 0x01;
232 break;
233 case 6:
234 fastPin = GPIO_FAST_ID_QUARK_NC_CW(0x02);
235 highValue = 0x02;
236 break;
237 case 9:
238 fastPin = GPIO_FAST_ID_QUARK_NC_RW(0x04);
239 highValue = 0x04;
240 break;
241 case 10:
242 fastPin = GPIO_FAST_ID_QUARK_SC(0x04);
243 highValue = 0x04;
244 break;
245 case 11:
246 fastPin = GPIO_FAST_ID_QUARK_NC_RW(0x08);
247 highValue = 0x08;
248 break;
249 case 12:
250 fastPin = GPIO_FAST_ID_QUARK_SC(0x80);
251 highValue = 0x80;
252 break;
253 case 13:
254 fastPin = GPIO_FAST_ID_QUARK_NC_RW(0x20);
255 highValue = 0x20;
256 break;
257 default:
258 highValue = 1;
259 break;
260 }
261 }
262 else
263 {
264 switch(_inpin)
265 {
266 case 2:
267 fastPin = GPIO_FAST_ID_QUARK_SC(0x40);
268 highValue = 0x40;
269 break;
270 case 3:
271 fastPin = GPIO_FAST_ID_QUARK_SC(0x80);
272 highValue = 0x80;
273 break;
274 default:
275 highValue = 1;
276 break;
277 }
278 }
279 a = micros();
280 while(fastGpioDigitalRead(fastPin) == 0)
281 {
282 b= micros();
283 if((b - a) >= timeout)
284 {
285 break;
286 }
287 }
288 a = micros();
289 while(fastGpioDigitalRead(fastPin) == highValue)
290 {
291 b= micros();
292 if((b - a) >= timeout)
293 {
294 break;
295 }
296 }
297 return (b - a);
298 return 0;
299 }
300
301
302 int DHT::bitsToByte(int bits[])
303 {
304 int data = 0;
305 for(int i = 0; i < 8; i++)
306 {
307 if (bits[i])
308 {
309 data |= (int)(1 << (7 - i));
310 }
311 }
312 return data;
313 }
1 // Example testing sketch for various DHT humidity/temperature sensors
2 // Written by ladyada, public domain
3
4 #include "DHT.h"
5
6 #define DHTIN 2 // what pin we‘re connected to
7 #define DHTOUT 3
8
9 // Uncomment whatever type you‘re using!
10 #define DHTTYPE DHT11 // DHT 11
11 //#define DHTTYPE DHT22 // DHT 22 (AM2302)
12 //#define DHTTYPE DHT21 // DHT 21 (AM2301)
13
14 // Connect pin 1 (on the left) of the sensor to +5V
15 // Connect pin 2 of the sensor to whatever your DHTPIN is
16 // Connect pin 4 (on the right) of the sensor to GROUND
17 // Connect a 10K resistor from pin 2 (data) to pin 1 (power) of the sensor
18
19 DHT dht(DHTIN,DHTOUT, DHTTYPE);
20
21 void setup() {
22 Serial.begin(9600);
23 Serial.println("DHTxx test!");
24
25 dht.begin();
26 }
27
28 void loop() {
29 // Wait a few seconds between measurements.
30 delay(2000);
31
32 // Reading temperature or humidity takes about 250 milliseconds!
33 // Sensor readings may also be up to 2 seconds ‘old‘ (its a very slow sensor)
34 float h = dht.readHumidity();
35 // Read temperature as Celsius
36 float t = dht.readTemperature();
37 // Read temperature as Fahrenheit
38 float f = dht.readTemperature(true);
39
40 // Check if any reads failed and exit early (to try again).
41 if (isnan(h) || isnan(t) || isnan(f)) {
42 Serial.println("Failed to read from DHT sensor!");
43 return;
44 }
45
46 // Compute heat index
47 // Must send in temp in Fahrenheit!
48 float hi = dht.computeHeatIndex(f, h);
49
50 Serial.print("Humidity: ");
51 Serial.print(h);
52 Serial.print(" %\t");
53 Serial.print("Temperature: ");
54 Serial.print(t);
55 Serial.print(" *C ");
56 Serial.print(f);
57 Serial.print(" *F\t");
58 Serial.print("Heat index: ");
59 Serial.print(hi);
60 Serial.println(" *F");
61 }
原文地址：http://bigdinotech.com/tutorials/galileo-tutorials/using-1-wire-device-with-intel-galileo/