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  1. #1
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    I2C Communication for Honeywell pressure sensor

    Hi

    I am using Honeywell pressure sensor to measure pressure of air in a pipe.

    for this have to use I2C Communication with pic PIC16F1787

    circuit for this Click image for larger version. 

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    is my Circuit is perfect ? Help me out
    in programming side i used I2C protocol
    for Honeywell air pressure sensor's Digital I2C address is 0X49.
    to reading data from sensor
    the program flow are 1st master send data to slave
    >send start condition
    > send Digital address (0X48)
    > stop condition
    2ndly read data from slave means slave response to master
    > start condition
    > Digital address (0x49)
    > than reading data

    moreover for same program for RTC DS1307 slave
    i am getting data from RTC with RTC address in same program but i am not even getting garbage value for Honeywell sensor for same I2C pin and configuration

    so is there any programming change for this particular sensor
    is there any additional change for this sensor for I2C protocol programming

    Data sheet of Honeywell sensor is
    https://sensing.honeywell.com/honeyw...08268-5-en.pdf

    please help me out


    --

    Thank You

    Er. Nirmit Patel
    9925789327

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    Re: I2C Communication for Honeywell pressure sensor

    Hi,

    Perfect... what is perfect?
    I2C is a standardised interface. There are free specifications available. Go through them.
    If you meet all the specifications it should be perfect.
    But this is not only a hardware problem...it is a software problem, too.

    What do we see?
    Microcontroller: power supply and clock is missing and the whole circuit to program it.
    LCD and it's connections: has nothing to do with I2C. Power supply missing, contrast circuit missing.
    Honeywell sensor: It surely needs a power supply.
    Two resistors: Please read I2C specification about resistor values. I don't have them in mind.

    All the issues are "real world" issues. But I'm not sure if your Honeywell communication is a simulation problem or a real world problem.

    Generally...what do you need for a proper I2C communication:
    * power supply. Urgent. Some devices work with 3.3V, some with 5V, thus reading the datasheets is essential.
    * I2C signal levels. --> datasheet
    * I2C timing --> datasheets. The master clock frequency should be equal or smaller than the least specified frequency of all interface partners.
    * correct addressing--> datasheet. The most confusing is that some datasheets tell a 7 bit addres )that needs to be shifted) and some give an 8 bit address. Proper addressing is simply verified by checking the ACK bit.

    But what we don't see is the wiring. Short, low capacitance wiring. Use a scope to verify the signal quality.

    Code:
    >send start condition
    > send Digital address (0X48)
    > stop condition
    I assume there is something missing. Indeed it does nothing. Check datasheet if this procedure is correct. Afaik every datasheet contains a communication diagram.

    Klaus
    Please don´t contact me via PM, because there is no time to respond to them. No friend requests. Thank you.



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    Re: I2C Communication for Honeywell pressure sensor

    Which sensor do you exactly use? You are talking about pressure sensor, but the datasheet is for a digital flow sensor.

    The sensors are shipped with different I2C addresses. Did you check the type code in this regard?



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    Re: I2C Communication for Honeywell pressure sensor

    Quote Originally Posted by FvM View Post
    Which sensor do you exactly use? You are talking about pressure sensor, but the datasheet is for a digital flow sensor.

    The sensors are shipped with different I2C addresses. Did you check the type code in this regard?
    sorry it flow sensor only
    yes in data sheet they provide I2C address



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    Re: I2C Communication for Honeywell pressure sensor

    The program flow in post #1 doesn't make sense. You'll only send the write address, if you want to submit an actual command, e.g. power-on reset. Otherwise you'll only use the read address.

    I suppose that writing 0x48 respectively 0x49 is probably misunderstanding the address notation used by Honeywell. They are interpreting the leftmost 7 bits as address, respectively you'll write byte 0x90 and 0x91 as write and read address.

    - - - Updated - - -

    Or more likely 0x92 and 0x93, as the address is said to be 0x49.
    I2C Slave Address is the 7 Most Significant Bits for the first transmitted byte
    I notice that the data sheet has a typo in the write sequence, R/W bit erroneously 1, so other details may be wrong as well. Ultimately you can try all possible read addresses to see which get an acknowledge and data output.



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    Re: I2C Communication for Honeywell pressure sensor

    I don't see where you check that I2c slave device responding. When you send address it should return back ACK. Otherwise it is no point to continue communication.
    Love me or hate me. All infractions will be ignored.



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    Re: I2C Communication for Honeywell pressure sensor

    Quote Originally Posted by FvM View Post
    The program flow in post #1 doesn't make sense. You'll only send the write address, if you want to submit an actual command, e.g. power-on reset. Otherwise you'll only use the read address.

    I suppose that writing 0x48 respectively 0x49 is probably misunderstanding the address notation used by Honeywell. They are interpreting the leftmost 7 bits as address, respectively you'll write byte 0x90 and 0x91 as write and read address.

    - - - Updated - - -

    Or more likely 0x92 and 0x93, as the address is said to be 0x49.


    I notice that the data sheet has a typo in the write sequence, R/W bit erroneously 1, so other details may be wrong as well. Ultimately you can try all possible read addresses to see which get an acknowledge and data output.
    Thank You
    now i am reading data through I2C with your address 92 and 93



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    Honeywell air flow sensor Data reading analysis issue

    hi
    Please help me out for Honeywell Airflow sensor for reading proper date with appropriate Flow value.
    i am getting some data which in increasing by blowing sensor means if air is passing air flow value is increasing
    but i am unable to measure actual flow rate. i am not able to read proper sequence given in data sheet of sensor....
    how many byte of data to read...how many bit to discard and when to start reading.
    i want help in reading proper data for airflow but am not getting what exactly datasheet explained in it.
    i am attaching datasheet snapshot and full datasheet too

    https://sensing.honeywell.com/honeyw...08268-5-en.pdf

    https://sensing.honeywell.com/honeyw...08210-5-en.pdf

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    --
    Thank You

    Er. Nirmit Patel
    9925789327



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  9. #9
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    Re: Honeywell air flow sensor Data reading analysis issue

    You are apparently mixing documents of two slightly different Honeywell digital flow sensors. They seem to differ regarding which data is send in the first reads after startup but both are said to send 14 bit flow values after the startup. There's an additional option to request specific data by a write command, but you should be able to work without it.



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    Re: Honeywell air flow sensor Data reading analysis issue

    Quote Originally Posted by FvM View Post
    You are apparently mixing documents of two slightly different Honeywell digital flow sensors. They seem to differ regarding which data is send in the first reads after startup but both are said to send 14 bit flow values after the startup. There's an additional option to request specific data by a write command, but you should be able to work without it.
    both documents are same only..one is data sheet and 2nd is its technical note
    ya "regarding which data is send in the first reads after startup but both are said to send 14 bit flow values after the startup. "
    i read all this but my doubt is i am not able to get actual data and not come to know actual sequence of Reading data.
    what to request first ??? for reading data and what next for flow rate ?



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    Re: Honeywell air flow sensor Data reading analysis issue

    The data sheet is pretty clear about it. You do repeated 16 bit reads, that's it.



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