Diff: DS18B20.cpp

Revision:

0:769f9b2b30d5

diff -r 000000000000 -r 769f9b2b30d5 DS18B20.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/DS18B20.cpp	Fri Jul 05 22:14:08 2013 +0000
@@ -0,0 +1,133 @@
+#include "DS18B20.h"
+
+DS18B20::DS18B20(PinName pin, unsigned resolution) :
+    _pin(pin) {
+    SetResolution(resolution);
+}
+
+DS18B20::~DS18B20() {
+}
+
+// Reset 1-wire interface.
+unsigned DS18B20::Reset() {
+    _pin.output();
+    _pin = 0;    // drive bus low
+    wait_us(H);
+    _pin.input(); // release bus
+    wait_us(I);
+    unsigned result = _pin;  // read bus value
+    wait_us(J);
+    return result;
+}
+
+// Write bit to 1-wire.
+void DS18B20::WriteBit(unsigned bit) {
+    _pin.output();
+    if (bit) {
+        _pin = 0;        // drive bus low
+        wait_us(A);        // delay A
+        _pin.input();      // release bus
+        wait_us(B);        // delay B
+    } else {
+        _pin = 0;    // drive bus low
+        wait_us(C);    // delay C
+        _pin.input();  // release bus
+        wait_us(D);    // delay D
+    }
+}
+
+// Read bit from 1-wire.
+unsigned DS18B20::ReadBit() {
+    unsigned bit_value;
+    _pin.output();
+    _pin = 0;        // drive bus low
+    wait_us(A);        // delay A
+    _pin.input();      // release bus
+    wait_us(E);        // delay E
+    bit_value = _pin;    // master sample bus
+    wait_us(F);
+    return bit_value;
+}
+
+// Write byte to 1-wire.
+void DS18B20::WriteByte(unsigned byte) {
+    for (unsigned bit = 0; bit < 8; ++bit) {
+        WriteBit(byte & 0x01); // lsb to msb
+        byte >>= 1;    // right shift by 1-bit
+    }
+}
+
+// Read byte from 1-wire.
+unsigned DS18B20::ReadByte() {
+    unsigned byte = 0;
+    for (unsigned bit = 0; bit < 8; ++bit) {
+        byte |= (ReadBit() << bit);    // Reads lsb to msb
+    }
+    return byte;
+}
+
+// Set number of bits in the conversion.
+unsigned DS18B20::SetResolution(unsigned resolution) {
+    if (Reset() != 0)
+        return 1;
+    else {
+        WriteByte(SKIP_ROM);            // Skip ROM
+        WriteByte(WRITE_SCRATCHPAD);    // WRITE_SCRATCHPAD
+        WriteByte(0x7f);                // Alarm TH
+        WriteByte(0x80);                // Alarm TL
+        WriteByte(resolution);          // 0xx11111 xx=resolution (9-12 bits)
+    }
+    return 0;
+}
+
+// Trigger a temperature conversion but don't read the temperature.
+unsigned DS18B20::DoConversion() {
+    if (Reset() != 0)
+        return 1;
+    else {
+        WriteByte(SKIP_ROM);            // Skip ROM
+        WriteByte(CONVERT);             // Convert
+        while (ReadBit() == 0)
+            ; // wait for conversion to complete
+    }
+    return 0;
+}
+
+// Do Conversion and get temperature as s8.4 sign-extended to 16-bits.
+int DS18B20::RawTemperature() {
+    // Perform the temperature conversion.
+    if (DoConversion() != 0)
+        return INVALID_TEMPERATURE;
+    // Read the temperature back.
+    if (Reset() != 0)
+        return INVALID_TEMPERATURE;
+    else {
+        WriteByte(SKIP_ROM);    // Skip ROM
+        WriteByte(READ_SCRATCHPAD);    // Read Scrachpad
+        unsigned LSB = ReadByte();
+        unsigned MSB = ReadByte();
+        // Terminate read as we only want temperature
+        Reset();
+        // Ensure correct sign-extension.
+        return (int)((int16_t)((MSB << 8) | LSB));
+    }
+}
+
+// Read temperature in floating point format.
+float DS18B20::GetTemperature() {
+    int temperature = RawTemperature();
+    return ((float)temperature) / 16.0;
+}
+
+// Read back DS18B20 ROM.
+int DS18B20::ReadROM(DS18B20::ROM_Code_t *ROM_Code) {
+    if (Reset() != 0)
+        return 1;
+    else {
+        WriteByte(READ_ROM);    // Read ROM
+        for (unsigned i = 0; i < 8; ++i) {
+            ROM_Code->rom[i] = ReadByte();
+        }
+    }
+    return 0;
+}