Ubuntu Manpage: DS2450 - Quad A/D Converter

name
synopsis
family code
special properties
co2 (carbon dioxide) sensor properties
standard properties
alarms
description
addressing
datasheet
see also
availability
author

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] | latestvolt.[A-D|ALL] |
       latestvolt2.[A-D|ALL] ]]

       20  [.]XXXXXXXXXXXX[XX][/[  8bit/volt.[A-D|ALL]  |  8bit/volt2.[A-D|ALL]  |  8bit/latestvolt.[A-D|ALL]  |
       8bit/latestvolt2.[A-D|ALL] ]]

       20 [.]XXXXXXXXXXXX[XX][/[ memory | pages/page.[0-3|ALL] | power ]

       20   [.]XXXXXXXXXXXX[XX][/[  alarm/high.[A-D|ALL]  |  alarm/low.[A-D|ALL]  |  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] ]

       20 [.]XXXXXXXXXXXX[XX][/[ address | crc8 | id | locator | r_address | r_id | r_locator | type ]]

   CO2 sensor
       20 [.]XXXXXXXXXXXX[XX][/[ CO2/ppm | CO2/power | CO2/status ]

FAMILY CODE

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 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
Configure whether the DS2450 is externally powered (as opposed to parasitically powered from the data
line).
If configured as powered, the A/D coverter will be set to continuous sampling, and the bus will be
released during a single conversion allowing other devices to communicate.
Setting this to 1 when no power is applied to the chip's Vcc will result in wrong voltage readouts.
Setting this to 0 when power is applied to the chip's Vcc allows a simultaneous conversion trigger on all
DS2450 on a bus. The (always safe) default is 0.

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
volt2.A ... volt2.D volt2.ALL
8bit/volt.A ... 8bit/volt.D 8bit/volt.ALL
8bit/volt2.A ... 8bit/volt2.D 8bit/volt2.ALL
read-only, floating point
Reading one of these nodes triggers a conversion on the specified voltage input(s) with the selected
resolution (16 or 8 bit) and returns the sampled voltage(s) with the selected scaling (0 - 5.10V or 0 -
2.55V). The conversion time is about 1.4ms per input for 16-bit and 0.8ms per input for 8-bit. The
output feature ( PIO ) is disabled by reading the corresponding node.
ALL is an aggregate of the voltages. Sampling is controlled by the chip and done in the order A, B, C, D,
one after another.

latestvolt.A ... latestvolt.D latestvolt.ALL
latestvolt2.A ... latestvolt2.D latestvolt2.ALL
8bit/latestvolt.A ... 8bit/latestvolt.D 8bit/latestvolt.ALL
8bit/latestvolt2.A ... 8bit/latestvolt2.D 8bit/latestvolt2.ALL
read-only, floating point
Returns previously measured voltage on the specified input(s) with the selected scaling (0 - 5.10V or 0 -
2.55V). Resolution and scaling are set by sampling a voltage, not here; the correct latestvolt nodes
have to be read to make the result meaningful.
ALL is an aggregate of the voltages and returns all voltage values from the chip.
Reading these nodes will never trigger a voltage conversion. Intended for use in conjunction with
/simultaneous/voltage.

CO2 (Carbon Dioxide) SENSOR PROPERTIES

       The CO2 sensor is a device constructed from a SenseAir K30 and a DS2450

   CO2/power
       read-only, floating point
       Supply voltage to the CO2 sensor (should be around 5V)

   CO2/ppm
       read-only, unsigned
       CO2 level in ppm (parts per million). Range 0-5000.

   CO2/status
       read-only, yes-no
       Is the internal voltage correct (around 3.2V)?

STANDARD PROPERTIES

address
r_address
read-only, ascii
The entire 64-bit unique ID. Given as upper case hexadecimal 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 preceding 56 bits of
the unique ID number. Given as upper case hexadecimal digits (0-9A-F).

family
read-only, ascii
The 8-bit family code. Unique to each type of device. Given as upper case hexadecimal 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 hexadecimal 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 hexadecimal) 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 (DEPRECATED)
read-only, yes-no
Is the device currently present on the 1-wire bus?

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 Semiconductor, Inc.
The bus is a low-power low-speed low-connector scheme where the data line can also provide power.

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

The 1-wire scheme uses a single bus master and multiple slaves on the same wire. The bus master initiates
all communication. The slaves can be individually discovered and addressed using their unique ID.

Bus masters come in a variety of configurations including serial, parallel, i2c, network or USB adapters.

OWFS design
OWFS is a suite of programs that designed to make the 1-wire bus and its devices easily accessible. The
underlying principle is to create a virtual filesystem, with the unique ID being the directory, and the
individual properties of the device are represented as simple files that can be read and written.

Details of the individual slave or master design are hidden behind a consistent interface. The goal is to
provide an easy set of tools for a software designer to create monitoring or control applications. There
are some performance enhancements in the implementation, including data caching, parallel access to bus
masters, and aggregation of device communication. Still the fundemental goal has been ease of use,
flexibility and correctness rather than speed.

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 hexadecimal, 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

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

       CO2 sensor
              http://www.senseair.se/Datablad/k30%20.pdf

       CO2 device
              https://www.m.nu/co2meter-version-2-p-259.html?language=en

AVAILABILITY

       http://www.owfs.org

AUTHOR

       Paul Alfille (paul.alfille@gmail.com)