1. This forum section is a read-only archive which contains old newsgroup posts. If you wish to post a query, please do so in one of our main forum sections (here). This way you will get a faster, better response from the members on Motherboard Point.

CMOS Image sensor & Two-wire serial interface

Discussion in 'Embedded' started by Kcin, Nov 26, 2008.

  1. Kcin

    Kcin Guest

    Hi, I tried to look for similar topics in the archive but no luck.

    I have a cmos image sensor, and it has a "two-wire serial interface"
    to read/write its on-chip registers. I tried to treat it like a I2C
    protocol, and fed a 100KHz at SCL, and write an address byte at SDA,
    but cannot get the acknowledge bit.

    Is it about the values of pull-up resistors in SCL and SDA? Or the
    clocking frequency problem??


    Kcin, Nov 26, 2008
    1. Advertisements

  2. Kcin

    Kcin Guest

    It's a Micron's CMOS image sensor. The spec only describes both SCL
    and SDA should be pull up 3.3V with a 1.5k ohm resistors. No suggested
    clock rate of SCL. It does not have any signs of the word "i2c" as
    well, it calls it "Two-Wire Serial Interface". What standard is it

    "Serial Bus Description
    Registers are written to and read from the MT9T001 through the two-
    wire serial interface bus. The MT9T001 is a two-wire serial interface
    slave and is controlled by the two-wire serial clock (SCLK), which is
    driven by the two-wire serial interface master. Data is transferred
    into and out through the MT9T001 through the two-wire serial interface
    data (SDATA)
    line. The SDATA line is pulled up to 3.3V off-chip by a 1.5KÙ
    resistor. Either the slave or master device can pull the SDATA line
    down--the two-wire serial interface protocol determines which device is
    allowed to pull the SDATA line down at any given time."
    Kcin, Nov 27, 2008
    1. Advertisements

  3. I2C interfaces often aren't called I2C, presumably due to possible licensing/patent issues or subtle
    implementration differences. However the required waveforms will be in the datasheet.
    Mike Harrison, Nov 27, 2008
  4. Kcin

    jakiechon Guest

    I am actually working on the same thing and can not get an acknowledge

    I am running from the LH a SCL of 100KHz and my PIXCLOCK (which is the
    master for the MT9T001) at ~ 2.5 MHz.

    For some reason I still cannot get an acknowledge bit on I2C.

    I checked the timing diagrams and a 2.5MHz clock should meet the
    minimum by far, but still nothing...

    Anybody got any ideas?

    jakiechon, Nov 29, 2008
  5. Kcin

    Kcin Guest

    I tried to feed 100KHz and 400KHz to SCL @ 48MHz master clock, but
    still no ack bit.

    I will try to lower SCL to 80KHz.

    More, I am wondering if SCL depends on the master clock.

    I read several specs and it seems that many of their cmos run with
    this "2-wire serial interface". What is the trick really?


    Kcin, Nov 29, 2008
  6. Which timings have you checked? Video or I2C?

    I would actually suggesting capturing your I2C communications on
    a digital scope and checking what is happening and that your are sending
    the right information.

    Often these sorts of problems end up as

    Incorrect bit pattern (address/data)
    Incorrect waiting for bit times
    incorrect or open connections
    incorrect voltage levels used
    incorrect I2C termination
    incorrect oscillator on imager
    Some other configuration on the imager missing/wrong

    It is very, very rarely the device at fault, sometimes the documentation.
    Paul Carpenter |
    <http://www.pcserviceselectronics.co.uk/> PC Services
    <http://www.pcserviceselectronics.co.uk/fonts/> Timing Diagram Font
    <http://www.gnuh8.org.uk/> GNU H8 - compiler & Renesas H8/H8S/H8 Tiny
    <http://www.badweb.org.uk/> For those web sites you hate
    Paul Carpenter, Jun 30, 2010
    1. Advertisements

Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.