Forums

CMOS Image sensor & Two-wire serial interface

Started by Kcin November 26, 2008
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??

Thanks.

Kcin
Kcin wrote:
> 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?? > > Thanks. > > Kcin
yes. Or it might be something else. What does the data sheet tell you? ** Posted from http://www.teranews.com **
On Nov 27, 2:48 pm, Bob <SkiBoy...@excite.com> wrote:
> Kcin wrote: > > 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?? > > > Thanks. > > > Kcin > > yes. > Or it might be something else. What does the data sheet tell you? > ** Posted fromhttp://www.teranews.com**
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 really? "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 1.5K=D9 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."
On Thu, 27 Nov 2008 06:56:21 -0800 (PST), Kcin <takit.lau@gmail.com> wrote:

>On Nov 27, 2:48 pm, Bob <SkiBoy...@excite.com> wrote: >> Kcin wrote: >> > 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?? >> >> > Thanks. >> >> > Kcin >> >> yes. >> Or it might be something else. What does the data sheet tell you? >> ** Posted fromhttp://www.teranews.com** > >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 >really?
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.
Kcin wrote:
> On Nov 27, 2:48 pm, Bob <SkiBoy...@excite.com> wrote: >> Kcin wrote: >>> 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?? >>> Thanks. >>> Kcin >> yes. >> Or it might be something else. What does the data sheet tell you? >> ** Posted fromhttp://www.teranews.com** > > 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 > really? > > "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 1.5K&#2013265945; > 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."
you need to get the full data sheet. Omnivision made us sign a NDA. Micron (Aptina) might require it too. Contact Aptina or their distributor if you have to. Bob ** Posted from http://www.teranews.com **
>On Nov 27, 2:48 pm, Bob <SkiBoy...@excite.com> wrote:
>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.
According to the datasheet at http://download.micron.com/pdf/datasheets/imaging/MT9T001_3100_DS.pdf "The two-wire serial bus operation requires certain minimum master clock cycles between transitions. These are specified in the following diagrams in master clock cycles."... and then there are a bunch of timing diagrams to peruse.
On Nov 28, 3:06=A0am, "srl100" <srl...@yahoo.com> wrote:
> >On Nov 27, 2:48 pm, Bob <SkiBoy...@excite.com> wrote: > >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. > > According to the datasheet athttp://download.micron.com/pdf/datasheets/im=
aging/MT9T001_3100_DS.pdf
> > "The two-wire serial bus operation requires certain minimum master clock > cycles between transitions. These are specified in the following diagrams > in master clock cycles."... > > and then there are a bunch of timing diagrams to peruse.
I am actually working on the same thing and can not get an acknowledge either. 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? --Daniel
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?

Thanks.

Kicn

On Nov 29, 9:51=A0am, jakiec...@gmail.com wrote:
> On Nov 28, 3:06=A0am, "srl100" <srl...@yahoo.com> wrote: > > > >On Nov 27, 2:48 pm, Bob <SkiBoy...@excite.com> wrote: > > >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. > > > According to the datasheet athttp://download.micron.com/pdf/datasheets/=
imaging/MT9T001_3100_DS.pdf
> > > "The two-wire serial bus operation requires certain minimum master cloc=
k
> > cycles between transitions. These are specified in the following diagra=
ms
> > in master clock cycles."... > > > and then there are a bunch of timing diagrams to peruse. > > I am actually working on the same thing and can not get an acknowledge > either. > > 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? > > --Daniel
Did anyone ever resolve this issue.  I am trying to write to a similir
image sensor and not receiving the ACK.  I am using a bit bang I2C
implementation.  I have reviewed the image sensor timings and I am well
within spec.

Thanks,
Elliott

	   
					
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Posted through http://www.EmbeddedRelated.com
In article <ie2dnXh0v4F10LfRnZ2dnUVZ_vmdnZ2d@giganews.com>, 
elliott.nelson@n_o_s_p_a_m.charter.net says...
> Did anyone ever resolve this issue. I am trying to write to a similir > image sensor and not receiving the ACK. I am using a bit bang I2C > implementation. I have reviewed the image sensor timings and I am well > within spec.
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.
> Thanks, > Elliott > > > > --------------------------------------- > Posted through http://www.EmbeddedRelated.com >
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