DS2450(3)

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][/[

See the file man3/standard_mini.3so.

]]

CO2 sensor

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

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/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)?

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