DS2450(3)

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][/[ ]]

  CO2 sensor

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

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 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

ALARMS
None.

DESCRIPTION

  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

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

SEE ALSO

AVAILABILITY
http://www.owfs.org

AUTHOR
Paul Alfille (paul.alfille@gmail.com)