DS2450 − Quad A/D Converter
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][/[ ]]
20 [.]XXXXXXXXXXXX[XX][/[ CO2/ppm | CO2/power | CO2/status ]
20
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
read-write,
binary
32 bytes of data. Much has special implications. See the
datasheet.
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.
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.
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.
read-write,
yes-no
Enabled status of the voltage threshold. 1 is on. 0 is
off.
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
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.
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.
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.
The CO2 sensor is a device constructed from a SenseAir K30 and a DS2450
read-only,
floating point
Supply voltage to the CO2 sensor (should be around 5V)
read-only,
unsigned
CO2 level in ppm (parts per million). Range 0-5000.
read-only,
yes-no
Is the internal voltage correct (around 3.2V)?
None.
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
|
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
http://www.owfs.org
Paul Alfille ([email protected])