Revision 0:433af64321d5, committed 2015-03-15

Comitter:

hudakz

Date:

Sun Mar 15 14:16:16 2015 +0000

Child:

1:e4689408d617

Commit message:

Dallas' DS1820 family temperature sensor

Changed in this revision

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/DS1820.cpp	Sun Mar 15 14:16:16 2015 +0000
@@ -0,0 +1,201 @@
+#include "DS1820.h"
+
+#define DEBUG 1
+
+#if DEBUG
+extern Serial serial;
+#endif
+
+/**
+ * @brief   Constructs a generic DS1820 sensor
+ * @note    begin() must be called to detect and initialize the actual model
+ * @param   Name of data pin
+ * @retval
+ */
+DS1820::DS1820(PinName pin) :
+    oneWire(pin) {
+    present = 0;
+    type_s = 0;
+}
+
+/**
+ * @brief   Constructs a specific model
+ * @note    No need to call begin() to detect and initialize the model
+ * @param   One character model name: 'S', 's', 'B' or 'b'
+ *          Name of data pin
+ * @retval
+ */
+DS1820::DS1820(char model, PinName pin) :
+    oneWire(pin) {
+    if((model == 'S') or (model == 's')) {
+        present = 1;
+        type_s = 1;
+    }
+    else if((model == 'B') or (model == 'b')) {
+        present = 1;
+        type_s = 0;
+    }
+    else
+        present = 0;
+}
+
+/**
+ * @brief   Detects and initializes the actual DS1820 model
+ * @note
+ * @param
+ * @retval  true:   if a DS1820 family sensor was detected and initialized
+            false:  otherwise
+ */
+bool DS1820::begin(void) {
+    oneWire.reset_search();
+    wait_ms(250);
+    if(!oneWire.search(addr)) {
+#if DEBUG
+        serial.printf("No addresses.\r\n");
+#endif
+        oneWire.reset_search();
+        wait_ms(250);
+        return false;
+    }
+
+#if DEBUG
+    serial.printf("ROM =");
+    for(uint8_t i = 0; i < 8; i++) {
+        serial.printf(" %x", addr[i]);
+    }
+    serial.printf("\r\n");
+#endif
+
+    if(OneWire::crc8(addr, 7) == addr[7]) {
+        present = 1;
+
+        // the first ROM byte indicates which chip
+        switch(addr[0]) {
+        case 0x10:
+            type_s = 1;
+#if DEBUG
+            serial.printf("DS18S20 or old DS1820\r\n");
+#endif            
+            break;
+
+        case 0x28:
+            type_s = 0;
+#if DEBUG
+            serial.printf("DS18B20\r\n");
+#endif            
+            break;
+
+        case 0x22:
+            type_s = 0;
+#if DEBUG
+            serial.printf("DS1822\r\n");
+#endif            
+            break;
+
+        default:
+            present = 0;
+#if DEBUG
+            serial.printf("Device doesn't belong to the DS1820 family\r\n");
+            return false;
+#endif            
+        }
+        return true;
+    }
+#if DEBUG    
+    else {
+        serial.printf("Invalid CRC!\r\n");
+        return false;
+    }
+#endif    
+}
+
+/**
+ * @brief   Starts temperature conversion
+ * @note    The time to complete the converion depends on the selected resolusion
+ * @param
+ * @retval
+ */
+void DS1820::startConversion(void) {
+    if(present) {
+        oneWire.reset();
+
+        //oneWire.select(addr);
+        oneWire.skip();
+        oneWire.write(0x44);    //start conversion
+    }
+}
+
+/**
+ * @brief   Reads temperature from the chip's scratchpad
+ * @note
+ * @param
+ * @retval  Floating point temperature value
+ */
+float DS1820::read(void) {
+    if(present) {
+        oneWire.reset();
+        oneWire.skip();
+        oneWire.write(0xBE);            // to read Scratchpad
+        for(uint8_t i = 0; i < 9; i++)
+            data[i] = oneWire.read();
+
+        // Convert the raw bytes to a 16bit signed fixed point value :
+        // 1 sign bit, 7 integer bits, 8 fractional bits (two’s compliment
+        // ie. the LSB of the 16bit binary number represents 1/256th of a unit).
+
+        uint16_t*   p_word = reinterpret_cast < uint16_t * > (&data[0]);
+
+#if DEBUG
+        serial.printf("raw = %#x\r\n", *p_word);
+#endif            
+
+
+        if(type_s) {
+            *p_word = *p_word << 3;     // default 9 bit resolution
+            if(data[7] == 0x10) {
+
+                // "count remain" gives full 12 bit resolution
+                *p_word = (*p_word & 0xFFF0) + 12 - data[6];
+            }
+
+            *p_word = *p_word << 4;
+            return(toFloat(*p_word));
+        }
+        else {
+            uint8_t cfg = (data[4] & 0x60);
+            // at lower res, the low bits are undefined, so let's zero them
+
+            if(cfg == 0x00)
+                *p_word = *p_word &~7;  // 9 bit resolution, 93.75 ms
+            else
+            if(cfg == 0x20)
+                *p_word = *p_word &~3;  // 10 bit res, 187.5 ms
+            else
+            if(cfg == 0x40)
+                *p_word = *p_word &~1;  // 11 bit res, 375 ms
+            *p_word = *p_word << 4;     // default is 12 bit resolution
+            return(toFloat(*p_word));
+        }
+    }
+    else
+        return 0;
+}
+
+/**
+ * @brief   Converts a 16bit signed fixed point value to float
+ * @note    The 16bit unsigned integer represnts actually
+ *          a 16bit signed fixed point value:
+ *          1 sign bit, 7 integer bits, 8 fractional bits
+ *          (two’s compliment ie. the LSB of the 16bit binary number 
+ *           represents 1/256th of a unit).       
+ * @param   16bit unsigned integer
+ * @retval  Floating point temperature value
+ */
+float DS1820::toFloat(uint16_t word) {
+    //word = word << 4;
+    if(word & 0x8000)
+        return (-float(uint16_t(~word + 1)) / 256.0f);
+    else
+        return (float(word) / 256.0f);
+}
+

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/DS1820.h	Sun Mar 15 14:16:16 2015 +0000
@@ -0,0 +1,22 @@
+#ifndef DS1820_H_
+    #define DS1820_H_
+
+    #include <OneWire.h>
+
+class   DS1820
+{
+    OneWire oneWire;
+    uint8_t present;
+    uint8_t type_s;
+    uint8_t data[12];
+    uint8_t addr[8];
+    float   toFloat(uint16_t word);
+public:
+    DS1820(PinName pin);
+    DS1820(char model, PinName pin);
+    bool   begin(void);
+    void   startConversion(void);
+    float  read(void);
+
+};
+#endif /* DS1820_H_ */