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Table of Contents

Name

DS2450 - Quad A/D Converter

Synopsis

Voltage * 4 and Memory.

20 [.]XXXXXXXXXXXX[XX][/[ PIO.[A-D|ALL] | volt.[A-D|ALL] | volt2.[A-D|ALL] ]]

20 [.]XXXXXXXXXXXX[XX][/[ alarm/high.[A-D|ALL] | alarm/low.[A-D|ALL] | memory | pages/page.[0-3|ALL] | PIO.[A-D|ALL] | power | set_alarm/high.[A-D|ALL] | set_alarm/low.[A-D|ALL] | set_alarm/unset | set_alarm/volthigh.[A-D|ALL] | set_alarm/volt2high.[A-D|ALL] | set_alarm/voltlow.[A-D|ALL] | set_alarm/volt2low.[A-D|ALL] | volt.[A-D|ALL] | volt2.[A-D|ALL] | address | crc8 | id | locator | present | r_address | r_id | r_locator | type ]]

Family Code

20

Special Properties

alarm/high.A ... alarm/high.D alarm.high.ALL

alarm/high.A ... alarm/high.D alarm.high.ALL

read-write, binary
The alarm state of the voltage channel. The alarm state is set one of two ways:
voltage conversion
Whenever the DS2450 measures a voltage on a channel, that voltage is compared to the high and low limits set_alarm/volthigh and/or set_alarm/voltlow and if the alarm is enabled set_alarm/high and/or set_alarm/low the corresponding flag is set in alarm/high and/or alarm/low
manual set
The flag can be set by a direct write to alarm/high or alarm/low

memory

read-write, binary
32 bytes of data. Much has special implications. See the datasheet.

pages/page.0 ... pages/page.3.html pages/page.ALL

read-write, binary
Memory is split into 4 pages of 8 bytes each. Mostly for reading and setting device properties. See the datasheet for details.
ALL is an aggregate of the pages. Each page is accessed sequentially.

Pio.a ... Pio.d Pio.all

read-write, yes-no
Pins used for digital control. 1 turns the switch on (conducting). 0 turns the switch off (non-conducting).
Control is specifically enabled. Reading volt will turn off this control.
ALL is an aggregate of the voltages. Readings are made separately.

power

read-write, yes-no
Is the DS2450 externally powered? (As opposed to parasitically powered from the data line).
The analog A/D will be kept on continuously. And the bus will be released during a conversion allowing other devices to communicate.
Set true (1) only if Vcc powered (not parasitically powered). Unfortunately, the DS2450 cannot sense it’s powered state. This flag must be explicitly written, and thus is a potential source of error if incorrectly set.
It is always safe to leave power set to the default 0 (off) state.

set_alarm/high.A ... set_alarm/high.D set_alarm/high.ALL

set_alarm/low.A ... set_alarm/low.D set_alarm/low.ALL

read-write, yes-no
Enabled status of the voltage threshold. 1 is on. 0 is off.

set_alarm/volthigh.A ... set_alarm/volthigh.D set_alarm/volthigh.ALL

set_alarm/volt2high.A ... set_alarm/volt2high.D set_alarm/volt2high.ALL

set_alarm/voltlow.A ... set_alarm/voltlow.D set_alarm/voltlow.ALL

set_alarm/volt2low.A ... set_alarm/volt2low.D set_alarm/volt2low.ALL

read-write, floating point
The upper or lower limit for the voltage measured before triggering an alarm.
Note that the alarm must be enabled alarm/high or alarm.low and an actual reading must be requested volt for the alarm state to actually be set. The alarm state can be sensed at alarm/high and alarm/low

set_alarm/unset

read-write, yes-no
Status of the power-on-reset (POR) flag.
The POR is set when the DS2450 is first powered up, and will match the alarm state until explicitly cleared. (By writing 0 to it).
The purpose of the POR is to alert the user that the chip is not yet fully configured, especially alarm thresholds and enabling.

volt.A ... volt.D volt.ALL

read-only, floating point
Voltage read, 16 bit resolution. Range 0 - 5.10V.
Output ( PIO ) is specifically disabled.
ALL is an aggregate of the voltages. Readings are made separately.

volt2.A ... volt2.D volt2.ALL

read-only, floating point
Voltage read, 16 bit resolution. Range 0 - 2.55V.
Output ( PIO ) is specifically disabled.
ALL is an aggregate of the voltages. Readings are made separately.

Standard Properties

address

r_address

read-only, ascii
The entire 64-bit unique ID. Given as upper case hexidecimal digits (0-9A-F).
address starts with the family code
r address is the address in reverse order, which is often used in other applications and labeling.

crc8

read-only, ascii
The 8-bit error correction portion. Uses cyclic redundancy check. Computed from the preceeding 56 bits of the unique ID number. Given as upper case hexidecimal digits (0-9A-F).

family

read-only, ascii
The 8-bit family code. Unique to each type of device. Given as upper case hexidecimal digits (0-9A-F).

id

r_id

read-only, ascii
The 48-bit middle portion of the unique ID number. Does not include the family code or CRC. Given as upper case hexidecimal digits (0-9A-F).
r id is the id in reverse order, which is often used in other applications and labeling.

locator

r_locator

read-only, ascii
Uses an extension of the 1-wire design from iButtonLink company that associated 1-wire physical connections with a unique 1-wire code. If the connection is behind a Link Locator the locator will show a unique 8-byte number (16 character hexidecimal) starting with family code FE.
If no Link Locator is between the device and the master, the locator field will be all FF.
r locator is the locator in reverse order.

present

read-only, yes-no
Is the device currently present on the 1-wire bus?
Note, this means that each hex byte (2 characters) is reversed, not the text string.

type

read-only, ascii
Part name assigned by Dallas Semi. E.g. DS2401 Alternative packaging (iButton vs chip) will not be distiguished.

Alarms

None.

Description

1-Wire

1-wire is a wiring protocol and series of devices designed and manufactured by Dallas Semicondictor, Inc. The bus is a low-power low-speed low-connector scheme where the data line can also provide power.

Each device is uniquely unalterably numbered during manufacture. There is a wide variety of devices, including memory, sensors (humidity, temperature, voltage, contact, current), switches, timers, loggers, and more complex devices (like thermocouple sensors) can be built wit hte basic devices. There are also 1-wire devices that have encryption included.

The 1-wire bus is accessed via one of a number of serial, parallel or USB adapters.

OWFS design

OWFS is a suite of programs that fundementally make the 1-wire bus and its devices easily accessible. The underlying priciple is to create a virtual filesystem, with the unique ID being the directory, and the individual properties of the device files.

There is optional data caching to improved performance, but possible confusion over stale data.

Ds2450

The DS2450 (3) is a (supposedly) high resolution A/D converter with 4 channels. Actual resolutin is reporterd to be 8 bits. The channels can also function as switches. Voltage sensing (with temperature and current, but sometimes restricted voltrage ranges) can also be obtained with the DS2436 , DS2438 and DS276x

Addressing

All 1-wire devices are factory assigned a unique 64-bit address. This address is of the form:
Family Code
8 bits
Address
48 bits
CRC
8 bits

Addressing under OWFS is in hexidecimal, of form:
01.123456789ABC

where 01 is an example 8-bit family code, and 12345678ABC is an example 48 bit address.

The dot is optional, and the CRC code can included. If included, it must be correct.

Datasheet

http://pdfserv.maxim-ic.com/en/ds/DS2450.pdf

See Also

Programs

owfs (1) owhttpd (1) owftpd (1) owserver (1)

Language bindings

owtcl (3) owperl (3)

Clocks

DS1427 (3) DS1904(3) DS1994 (3) DS2404 (3) DS2404S (3) DS2415 (3) DS2417 (3)

ID

DS2401 (3) DS1990A (3)

Memory

DS1982 (3) DS1985 (3) DS1986 (3) DS1991 (3) DS1992 (3) DS1993 (3) DS1995 (3) DS1996 (3) DS2431 (3) DS2433 (3) DS2502 (3) DS2506 (3) DS2804 (3)

Switches

DS2405 (3) DS2406 (3) DS2408 (3) DS2409 (3) DS2413 (3)

Temperature

DS1822 (3) DS18B20 (3) DS18S20 (3) DS1920 (3) DS1921 (3) DS1821 (3)

Humidity

DS1922 (3)

Voltage

DS2450 (3)

Resistance

DS2890 (3)

Multifunction

DS2436 (3) DS2438 (3) DS2760 (3)

Counter

DS2423 (3)

LCD Screen

LCD (3) DS2408 (3)

Crypto

DS1977 (3)

Availability

http://owfs.sourceforge.net

Author

Paul Alfille (palfille@earthlink.net)


Table of Contents

© 2003-4 Paul H. Alfille and The owfs Team
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