Arduino library for I2C ASDX pressure sensor.

The ASDX sensor of Honeywell exist in many variations. Check the datasheet of your type for all the details.

The I2C_ASDX library can read the sensor and give the pressure in millibar, bar or PSI or many other units. See below.

Pressure is measured in 14 bit = 16384 "steps", from which 80% is actually used.

Feedback, as always, is welcome.

Version 0.4.0 introduced a breaking change. You cannot set the pins in begin() any more. This reduces the dependency of processor dependent Wire implementations. The user has to call Wire.begin() and can optionally set the Wire pins before calling begin().

Always check datasheet for the exact pins.

        ASDX              ARDUINO
    +----------+        +----------+
    |          |        |          |
    |     GND o|--------|o GND     |
    |     VCC o|--------|o VCC     |
    |     SDA o|--------|o SDA     |
    |     SCL o|--------|o SCL     |
    |          |        |          |
    +----------+        +----------+

• https://github.com/RobTillaart/pressure - pressure conversions
• https://github.com/RobTillaart/Temperature - temperature conversions
• https://github.com/RobTillaart/I2C_ASDX - (I2C) pressure + conversions
• https://github.com/RobTillaart/MS4525DO - (I2C) temperature pressure sensor
• https://github.com/RobTillaart/MS5837 - (I2C) temperature pressure sensor (incl pressure to altitude)
• https://github.com/RobTillaart/MS5611 - (I2C) temperature pressure sensor (incl pressure to altitude)
• https://github.com/RobTillaart/MSP300 - (I2C) industrial pressure transducer
• https://swharden.com/blog/2017-04-29-precision-pressure-meter-project/

#include "I2C_ASDX.h"

• I2C_ASDX(uint8_taddress, uint8_t psi, TwoWire *wire = &Wire) Constructor, I2C address and maximum pressure. Optional the wire interface can be defined.
• bool begin() initializes internals. Returns true if address can be found on I2C bus.
• void reset() resets internal variables, including pressure.
• bool isConnected() tests if address can be found on I2C bus.
• uint8_t getAddress() returns I2C address used. Mainly for debug message.

Before any call to getPressure() one need to call read() unless one wants the last value read.

• int read() actually reads the sensor, checks for errors, calculates the pressure and set the lastRead timestamp. Returns I2C_ASDX_OK or an error code.

• int getPressure() returns pressure in milliBar. (rounded integer!). Returns 0 after a reset() and no read() done yet. Calling getPressure() (Or any of the other pressure functions) multiple times without read() will return the same value again.
• float getMilliBar() returns pressure in milliBar (float).
• float getBar() returns pressure in bar.
• float getPSI() returns pressure in PSI = Pounds per Square Inch.
• float getATM() returns pressure in Atmosphere.
• float getDynes() returns pressure in Dynes.
• float getInchHg() returns pressure in inches mercury.
• float getInchH2O() returns pressure in inches water.
• float getPascal() returns pressure in Pascal. Note this is the SI unit.
• float getTORR() returns pressure in TORR.
• float getCmHg() returns pressure in centimetre mercury.
• float getCmH2O() returns pressure in centimetre water.
• float getMSW() returns pressure in Meters of Sea Water. (under water pressure unit).

Related library: https://github.com/RobTillaart/pressure additional conversions.

• uint16_t errorCount() total counter for the number of errors occurred. Internal counter wraps after 65535.
• uint32_t lastRead() time in milliseconds of last successful read of the sensor.
• int state() last known state of read, also returned by read()

Raw counter API, for debugging or your own conversion.

• int rawPressureCount() idem.

The library is tested with only 3 different sensors, all of the PG type.

Code is prepared but not tested for 15, 5 and 1 PSI too.

    ID    UNIT       TYPE   DESCRIPTION
                              output is proportional to difference
    PG    PSI        Gage   * between applied pressure and atmospheric pressure
    MG    mBar       Gage   * idem
    BG    Bar        Gage   * idem
    KG    KiloPascal Gage   * idem
     D    Differential      * between pressure applied to each of the ports.
     A    Absolute          * between applied pressure and built-in reference to vacuum.


    ADDRESS   PRESSURE   RANGE          TYPE      P   A T V
    0x58      100 psi    0..6895 mBar   SSCDANN 100PG 5 A 5
    0x38       60 psi    0..4137 mbar   SSCDANN 060PG 3 A 5
    0x28       30 psi    0..2068 mbar   SSCDANN 030PG 2 A 5

    P = pressure range
    A = I2C address indicator
    T = accuracy range
    V = voltage (3 volt also supported, not tested)

That said it is expected that the library is modifiable to support many more as long as they have the following raw read values.

    1638  =   0 PSI
    14746 = max PSI

(elaborate test table)

See examples

• update documentation.
• keep in sync with MS4525DO_RT

• int begin(float psi) to allow calibration or even arbitrary units.
  • return state?

• add real life examples if possible.
• add error/state code for after reset() and before read()
  • I2C_ASDX_NO_READ or I2C_ASDX_RESET
  • I2C_ASDX_NOT_INIT if begin() not called?
• C000 error => OVF ERROR (like MS4525?)

• pressure in N/m2 => pitot formula. v = sqrt(2 * pressure / rho);
  • rho is specific weight in kg/m3, depends on humidity temperature and height.
• remove less common pressure formats from lib (0.4.x ?)
  • are covered in pressure lib.
  • but they do no harm either.
• move code from .h to .cpp

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