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133 lines
2.9 KiB
C++
133 lines
2.9 KiB
C++
//
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// Continually measures temperatures at three points using the Dallas DS18B20 on three
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// separate Arduino pins.
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//
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// Uses the parasitic power mode
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//
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// Displays to a serial LCD operating at 9600 baud.
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//
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// Arduino Board DS18B20
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//
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// +5 VDC
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// |
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// 4.7K
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// 8 ---------------- |----- 2 (DQ) Note that terms 1 and 3 are grounded.
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//
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// 7 ---- same as above
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// 6 ---- same as above
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//
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// Tx ---------------------------- To Serial LCD (LCD #117)
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//
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// Peter H Anderson, Baltimore, MD, May 5, '07
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void setup()
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{
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int n, dev_channel[3] = {8, 7, 6}, _1W_Pin;
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for (n=0; n<1; n++)
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{
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_1W_Pin = dev_channel[n];
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digitalWrite(_1W_Pin, LOW);
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pinMode(_1W_Pin, INPUT); // sets the digital pin as input (logic 1)
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}
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Serial.begin(9600);
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delay(100);
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Serial.print("?B40"); // set backlight intensity
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delay(100);
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}
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void loop()
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{
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int n, dev_channel[3] = {8, 7, 6}, _1W_Pin;
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int HighByte, LowByte, TReading, SignBit, Tc_100, Whole, Fract;
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for (n=0; n<3; n++)
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{
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_1W_Pin = dev_channel[n];
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OneWireReset(_1W_Pin);
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OneWireOutByte(_1W_Pin, 0xcc, 0);
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OneWireOutByte(_1W_Pin, 0x44, 1); // perform temperature conversion, strong pullup for one sec
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OneWireReset(_1W_Pin);
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OneWireOutByte(_1W_Pin, 0xcc, 0);
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OneWireOutByte(_1W_Pin, 0xbe, 0);
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LowByte = OneWireInByte(_1W_Pin);
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HighByte = OneWireInByte(_1W_Pin);
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TReading = (HighByte << 8) + LowByte;
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SignBit = TReading & 0x8000; // test most sig bit
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if (SignBit) // negative
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{
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TReading = (TReading ^ 0xffff) + 1; // 2's comp
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}
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Tc_100 = (6 * TReading) + TReading / 4; // multiply by (100 * 0.0625) or 6.25
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Whole = Tc_100 / 100; // separate off the whole and fractional portions
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Fract = Tc_100 % 100;
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if (n==0) // if its the first time, clear the LCD
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{
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Serial.print("?f");
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delay(100);
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}
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if (SignBit) // If its negative
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{
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Serial.print("-");
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}
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Serial.print(Whole);
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Serial.print(".");
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if (Fract < 10)
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{
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Serial.print("0");
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}
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Serial.print(Fract);
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Serial.print("?n");
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}
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delay(5000); // 5 second delay. Adjust as necessary
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}
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void OneWireReset(int _1W_Pin) // reset. Should improve to act as a presence pulse
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{
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digitalWrite(_1W_Pin, LOW);
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pinMode(_1W_Pin, OUTPUT); // bring low for 500 us
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delayMicroseconds(500);
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pinMode(_1W_Pin, INPUT);
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delayMicroseconds(500);
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}
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void OneWireOutByte(int _1W_Pin, byte d, byte strong) // output byte d (least sig bit first).
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{
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byte n;
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for(n=8; n!=0; n--)
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{
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if ((d & 0x01) == 1) // test least sig bit
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{
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digitalWrite(_1W_Pin, LOW);
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pinMode(_1W_Pin, OUTPUT);
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delayMicroseconds(5);
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pinMode(_1W_Pin, INPUT);
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delayMicroseconds(60);
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}
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else
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{
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digitalWrite(_1W_Pin, LOW);
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pinMode(_1W_Pin, OUTPUT);
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delayMicroseconds(60);
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pinMode(_1W_Pin, INPUT);
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}
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d=d>>1; // now the next bit is in the least sig bit position.
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}
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if(strong)
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{
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digitalWrite(_1W_Pin, HIGH); // One sec of strong +5 VDC
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pinMode(_1W_Pin, OUTPUT);
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delay(1000);
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pinMode(_1W_Pin, INPUT);
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digitalWrite(_1W_Pin, LOW);
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}
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}
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