M Hey / DS18B20_1wire

Version of Richard Lane's library, with #define CABLE_EXT_DELAYS to extend reset() settling delays for extension cable

Fork of DS18B20_1wire by Richard Lane

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DS18B20 Class Reference
Data Structures | Public Types | Public Member Functions

DS18B20 Class Reference

A DS18B20 Dallas 1-wire digital thermometer interface. More...

#include <DS18B20.h>

Data Structures

union  ROM_Code_t
 Holds 8-byte internal ROM. More...
struct  ScratchPad_t
 Device onboard register layout (for reference only, not currently used) More...

Public Types

enum  
 

Value to return when Reset() fails.

More...
enum  RESOLUTION { RES_9_BIT = 0x1f, RES_10_BIT = 0x3f, RES_11_BIT = 0x5f, RES_12_BIT = 0x7f }
 

Temperature conversion dit width resolutions.

More...

Public Member Functions

 DS18B20 (PinName pin, unsigned resolution)
 Create a Dallas DS18B20 1-wire interface.
 ~DS18B20 ()
 Destructor.
float GetTemperature ()
 Performs conversion in DS18B20 and then reads and converts returned temperature to floating point.
unsigned DoConversion ()
 Performs conversion but does not read back temperature.
int RawTemperature ()
 The method that GetTemperature() calls to do all the conversion and reading but this method returns a 32-bit signed integer.
int ReadROM (ROM_Code_t *ROM_Code)
 Reads and returns the 8-byte internal ROM.
unsigned SetResolution (unsigned resolution)
 Sets the conversion resolution with RESOLUTION enum (9-12 bits signed)

Detailed Description

A DS18B20 Dallas 1-wire digital thermometer interface.

25 March,2014 added larger DELAY values to allow extra 1-bit bus settling time accommodating 3ft extension cable with higher parasitic capacitance.

Currently supports 9, 10, 11 or 12-bit conversions. Fewer bits require less conversion time from 93.75ms to 750ms. Also supports reading back the 8-byte internal ROM. Orignal code copied from DS18B20 C program by Niall Cooling (thanks!) and wrapped in C++ class by this library.

modified delay values to allow extra 1-bit bus settling time accommodating 3ft extension cable (with higher parasitic capacitance) define CABLE_EXT_DELAYS // extend reset() settling delays for extension cable

 #include "mbed.h"
 #include <stdint.h>
 #include "DS18B20.h"
 #define CABLE_EXT_DELAYS //longer reset() settling delays if extension cable

 Serial pc(USBTX, USBRX);     // serial comms over usb back to console
 DS18B20 thermom(p16, DS18B20::RES_12_BIT); // Dallas 1-wire

 int main() {
   pc.printf("DS18B20 Configuration\n\r");
   
   DS18B20::ROM_Code_t ROM_Code;
   thermom.ReadROM(&ROM_Code);
   pc.printf("Family code: 0x%X\n\r", ROM_Code.BYTES.familyCode);
   pc.printf("Serial Number: ");
   for (unsigned i = 6; i != 0; --i) {
       pc.printf("%02X%s", ROM_Code.BYTES.serialNo[i-1], (i != 1)?":":"\r\n");
   }
   pc.printf("CRC: 0x%X\r\n", ROM_Code.BYTES.CRC);
   
   pc.printf("\n\rRunning temperature conversion...\n\r");
   while (1) {
       pc.printf("Temperature is: %.4fC\n\r", thermom.GetTemperature());
       wait(10);
   }
 }

Definition at line 58 of file DS18B20.h.

Member Enumeration Documentation

anonymous enum

Value to return when Reset() fails.

Definition at line 62 of file DS18B20.h.

enum RESOLUTION

Temperature conversion dit width resolutions.

Enumerator:
RES_9_BIT 

93.75ms

RES_10_BIT 

187.5ms

RES_11_BIT 

375ms

RES_12_BIT 

750ms

Definition at line 65 of file DS18B20.h.

Constructor & Destructor Documentation

DS18B20 ( PinName  pin,
unsigned  resolution 
)

Create a Dallas DS18B20 1-wire interface.

Parameters:
pinPin to use for 1-wire interface (bidirectional I/O)
resolutionSets the conversion bit width (using RESOLUTION enum)

Definition at line 3 of file DS18B20.cpp.

~DS18B20 (  )

Destructor.

Definition at line 8 of file DS18B20.cpp.

Member Function Documentation

unsigned DoConversion (  )

Performs conversion but does not read back temperature.

Not needed if GetTemperature() is used as this calls DoConversion() itself.

Definition at line 84 of file DS18B20.cpp.

float GetTemperature (  )

Performs conversion in DS18B20 and then reads and converts returned temperature to floating point.

For many applications this is the only required method that needs to be used.

Definition at line 117 of file DS18B20.cpp.

int RawTemperature (  )

The method that GetTemperature() calls to do all the conversion and reading but this method returns a 32-bit signed integer.

The integer contains 4 fractional LSBs. Sometimes referred to as s28.4 format.

Definition at line 97 of file DS18B20.cpp.

int ReadROM ( DS18B20::ROM_Code_t *  ROM_Code )

Reads and returns the 8-byte internal ROM.

Definition at line 123 of file DS18B20.cpp.

unsigned SetResolution ( unsigned  resolution )

Sets the conversion resolution with RESOLUTION enum (9-12 bits signed)

Definition at line 70 of file DS18B20.cpp.

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