DS1820 Dallas 1-Wire Temperature Probe. More...

#include <DS1820.h>

Public Member Functions
	DS1820 (PinName data_pin, PinName power_pin)
	Create a probe object connected to the specified pins.
	DS1820 (PinName data_pin)
	Create a probe object connected to the specified pin this is used when all probes are externally powered.
void	read_RAM ()
	This function copies the DS1820's RAM into the object's RAM[].
void	search_ROM_setup ()
	This routine initializes the global variables used in the search_ROM() and search_alarm() funtions.
bool	search_ROM ()
	This routine will search for an unidentified device on the bus.
bool	search_alarm ()
	This routine will search for an unidentified device which has the temperature alarm bit set.
void	read_ROM ()
	This routine will read the ROM (Family code, serial number and Checksum) from a dedicated device on the bus.
int	convert_temperature (bool wait, devices device=this_device)
	This routine will initiate the temperature conversion within one or all DS1820 probes.
float	temperature (char scale='c')
	This function will return the probe temperature.
bool	ROM_checksum_error ()
	This function calculates the ROM checksum and compares it to the CRC value stored in ROM[7].
bool	RAM_checksum_error ()
	This function calculates the RAM checksum and compares it to the CRC value stored in RAM[8].
bool	set_configuration_bits (unsigned int resolution)
	This function sets the temperature resolution for the DS18B20 in the configuration register.
int	read_scratchpad ()
	This function returns the values stored in the temperature alarm registers.
void	write_scratchpad (int data)
	This function will store the passed data into the DS1820's RAM.
void	store_scratchpad (devices device=this_device)
	This function will transfer the TH and TL registers from the DS1820's RAM into the EEPROM.
int	recall_scratchpad (devices device=this_device)
	This function will copy the stored values from the EEPROM into the DS1820's RAM locations for TH and TL.
bool	read_power_supply (devices device=this_device)
	This function will return the type of power supply for a specific device.
Data Fields
char	ROM [8]
	ROM is a copy of the internal DS1820's ROM It is created during the search_ROM() or search_alarm() commands.
char	RAM [9]
	RAM is a copy of the internal DS1820's RAM It's updated during the read_RAM() command which is automaticaly called from any function using the RAM values except RAM_checksum_error.

Detailed Description

DS1820 Dallas 1-Wire Temperature Probe.

Example:

 #include "mbed.h"

 #include "TextLCD.h"
 #include "DS1820.h"

 TextLCD lcd(p25, p26, p21, p22, p23, p24, TextLCD::LCD16x2); // rs, e, d0-d3, layout

 const int MAX_PROBES = 16;
 DS1820* probe[MAX_PROBES];

 int main() {
     int i;
     int devices_found=0;
     // Initialize the probe array to DS1820 objects
     for (i = 0; i < MAX_PROBES; i++)
         probe[i] = new DS1820(p27);
     // Initialize global state variables
     probe[0]->search_ROM_setup();
     // Loop to find all devices on the data line
     while (probe[devices_found]->search_ROM() and devices_found<MAX_PROBES-1)
         devices_found++;
     // If maximum number of probes are found, 
     // bump the counter to include the last array entry
     if (probe[devices_found]->ROM[0] != 0xFF)
         devices_found++;
 
     lcd.cls();
     if (devices_found==0)
         lcd.printf("No devices found");
     else {
         while (true) {
             probe[0]->convert_temperature(true, DS1820::all_devices);
             lcd.cls();
             for (i=0; i<devices_found; i++) {
                 lcd.printf("%3.1f ",probe[i]->temperature('f'));
             }
         }
     }
 }

Definition at line 81 of file DS1820.h.

Constructor & Destructor Documentation

DS1820	(	PinName	data_pin,
		PinName	power_pin
	)

Create a probe object connected to the specified pins.

Parameters:

data_pin	DigitalInOut pin for the data bus
power_pin	DigitalOut pin to control the power MOSFET

Definition at line 10 of file DS1820.cpp.

DS1820 ( PinName data_pin )

Create a probe object connected to the specified pin this is used when all probes are externally powered.

Parameters:

data_pin DigitalInOut pin for the data bus

Definition at line 18 of file DS1820.cpp.

Member Function Documentation

int convert_temperature	(	bool	wait,
		devices	device = `this_device`
	)

This routine will initiate the temperature conversion within one or all DS1820 probes.

There is an optional built in delay (up to 750ms) to allow the conversion to complete.

To update all probes on the bus, use a statement such as this: probe[0]->convert_temperature(true, DS1820::all_devices);

Parameters:

wait	if true or parisitic power is used, waits up to 750 ms for conversion otherwise returns immediatly.
device	allows the function to apply to a specific device or to all devices on the 1-Wire bus.

Returns:: milliseconds untill conversion will complete.

Definition at line 252 of file DS1820.cpp.

bool RAM_checksum_error ( )

This function calculates the RAM checksum and compares it to the CRC value stored in RAM[8].

Approx 10 us on LPC1768.

Returns:: true if the checksums mis-matche, otherwise false.

Definition at line 211 of file DS1820.cpp.

bool read_power_supply ( devices device = this_device )

This function will return the type of power supply for a specific device.

It can also be used to query all devices looking for any device that is parasite powered.

Returns:: true if the device (or all devices) are Vcc powered, returns false if the device (or ANY device) is parasite powered.

Definition at line 398 of file DS1820.cpp.

void read_RAM ( )

This function copies the DS1820's RAM into the object's RAM[].

It is automaticaly called by temperature(), read_scratchpad(), and recall_scratchpad() of a single probe.

Definition at line 285 of file DS1820.cpp.

void read_ROM ( )

This routine will read the ROM (Family code, serial number and Checksum) from a dedicated device on the bus.

NOTE: This command can only be used when there is only one DS1820 on the bus. If this command is used when there is more than one slave present on the bus, a data collision will occur when all the DS1820s attempt to respond at the same time.

Definition at line 177 of file DS1820.cpp.

int read_scratchpad ( )

This function returns the values stored in the temperature alarm registers.

Returns:: a 16 bit integer of TH (upper byte) and TL (lower byte).

Definition at line 312 of file DS1820.cpp.

int recall_scratchpad ( devices device = this_device )

This function will copy the stored values from the EEPROM into the DS1820's RAM locations for TH and TL.

Parameters:

allows the function to apply to a specific device or to all devices on the 1-Wire bus.

Definition at line 344 of file DS1820.cpp.

bool ROM_checksum_error ( )

This function calculates the ROM checksum and compares it to the CRC value stored in ROM[7].

Returns:: true if the checksums mis-match, otherwise false.

Definition at line 202 of file DS1820.cpp.

bool search_alarm ( )

This routine will search for an unidentified device which has the temperature alarm bit set.

It uses the variables in search_ROM_setup to remember the pervious ROM address found. It will return FALSE if there were no new devices with alarms discovered on the bus.

Definition at line 90 of file DS1820.cpp.

bool search_ROM ( )

This routine will search for an unidentified device on the bus.

It uses the variables in search_ROM_setup to remember the pervious ROM address found. It will return FALSE if there were no new devices discovered on the bus.

Definition at line 86 of file DS1820.cpp.

void search_ROM_setup ( )

This routine initializes the global variables used in the search_ROM() and search_alarm() funtions.

It should be called once before looping to find devices.

Definition at line 166 of file DS1820.cpp.

bool set_configuration_bits ( unsigned int resolution )

This function sets the temperature resolution for the DS18B20 in the configuration register.

Parameters:

a	number between 9 and 12 to specify resolution

Returns:: true if successful

Definition at line 299 of file DS1820.cpp.

void store_scratchpad ( devices device = this_device )

This function will transfer the TH and TL registers from the DS1820's RAM into the EEPROM.

Note: There is a built in 10ms delay to allow for the completion of the EEPROM write cycle.

Parameters:

allows the fnction to apply to a specific device or to all devices on the 1-Wire bus.

Definition at line 331 of file DS1820.cpp.

float temperature ( char scale = 'c' )

This function will return the probe temperature.

Approximately 10ms per probe to read its RAM, do CRC check and convert temperature on the LPC1768. This function uses the count remainding values to interpolate the temperature to about 1/150th of a degree. Whereas the probe is not spec to that precision. It does seem to give a smooth reading to the tenth of a degree.

Parameters:

scale,may be either 'c' or 'f'

Returns:: temperature for that scale, or -1000.0 if CRC error detected.

Definition at line 363 of file DS1820.cpp.

void write_scratchpad ( int data )

This function will store the passed data into the DS1820's RAM.

Note: It does NOT save the data to the EEPROM for retention during cycling the power off and on.

Parameters:

a	16 bit integer of TH (upper byte) and TL (lower byte).

Definition at line 319 of file DS1820.cpp.

Field Documentation

char RAM[9]

RAM is a copy of the internal DS1820's RAM It's updated during the read_RAM() command which is automaticaly called from any function using the RAM values except RAM_checksum_error.

Definition at line 119 of file DS1820.h.

char ROM[8]

ROM is a copy of the internal DS1820's ROM It is created during the search_ROM() or search_alarm() commands.

ROM[0] is the Dallas Family Code ROM[1] thru ROM[6] is the 48-bit unique serial number ROM[7] is the device CRC

Definition at line 108 of file DS1820.h.

Type:	Library
Created:	07 Aug 2013
Imports:	487
Forks:	3
Commits:	5
Dependents:	0
Dependencies:	0
Followers:	8

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Field Documentation

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Member Function Documentation

Field Documentation

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