Misteaks happen :-) At least you are aware of the problem.
-- "If you want to post a followup via groups.google.com, don't use the broken "Reply" link at the bottom of the article. Click on "show options" at the top of the article, then click on the "Reply" at the bottom of the article headers." - Keith Thompson
Thanks for your answers all ! and thanks for the schematic
Just another question, how long does it take for the camera to answe
the read address ? I'm waiting 50us, I thought it was enough, bu apparently that could be the problem
Do you mean, "How long does it take the camera to take the SCCB data line low during the acknowledge bit time? (ie : after the transmission of the address bits A7 to A1 and R/W?"
Or do I misunderstand your question?
When I looked at the ACK timing with my oscilloscope, I could clearly see the microcontroller releasing the data line, and the OV7640 taking the data line low to ack. The low voltage levels were ever so slightly different, so it was easy to see the timing. I will have to get the scope out again to make the measurement you may be asking for.
Paul.
50us from what?
From SCL set low for the ACK bit? From SDA driven passive high?
What is the clock period for your address/data bits?
The fastest SCCB can be clocked is 100kHz, so 10us for each bit of
7 address bits, read/write bit, and ack bit, so the first address byte is 9 x 10us = 90us MINIMUM plus start I2C timing.If you are running at 100kHz, then wait at leat 90 if not 100us for the whole address and ack, *IF* you are using some form of I2C controller. If bit banging do a wait one each bit, slightly longer on ack.
You are still driving the SCL (SCCB clock) at that stage?
What frequency are you trying to drive SCCB at?
-- Paul Carpenter | snipped-for-privacy@pcserviceselectronics.co.uk PC Services GNU H8 & mailing list info For those web sites you hate
Yes, that's it I can also see the microcontroller releasing the data line, but the the level stays the same...
Thanks for the measurements
[quote:deef3a4c8b]Just another question, how long does it take fo the camera to answeDo you mean, "How long does it take the camera to take the SCCB dat line low during the acknowledge bit time? (ie : after the transmission o the address bits A7 to A1 and R/W?
Or do I misunderstand your question
When I looked at the ACK timing with my oscilloscope, I could clearl
see the microcontroller releasing the data line, and the OV7640 taking th data line low to ack. The low voltage levels were ever so slightl different, so it was easy to see the timing. I will have to get the scope out agai to make the measurement you may be asking for
Paul.[/quote:deef3a4c8b
=_NextPart_000_00B0_01C63640.905479E0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Since the above webpage is still getting a significant number of hits 8 = months later, to make the URL "permanent", I've copied the HTML to the = following URL :
The original will disappear in due course.
Paul.
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.