1. Home
  2. Hobby Electronics Basics
  3. simple oscillator circuit?

simple oscillator circuit?

Hi,

I am trying to use a at9sam7256 microcontroller.. i am using a programmable clock out line of this chip to drive a omnivision 9640 camera chip. The problem is that the clock signal seems very unstable.. i.e. the video comes out, but is very unstable and has a lot of noise. When i use the clock line that is on the omnivision reference board the camera data looks great.. so i know that the problem is the clock signal that i am feeding it since that is the only thing i changed.

Is there any way to clean up that clock signal that is coming from my microcontroller? I also dont mind creating a separate oscillator circuit with a 48mhz crystal.. but i am a newbie and i dont know how to create such a circuit... could someone explain? Also, are there single chip osclilators that simply have a clock out line that i could feed into the camera chip?

thanks - bob

Reply to
bbalonis
Loading thread data ...

are you using a crystal to clock the micro? how are you generating the clock using the micro?

there are single part oscilators.

Bye. Jasen

Reply to
Jasen Betts

Hi, Bob. You're not entirely clear on the frequency of the output signal you're feeding to your camera chip.

If you are feeding 48MHz, or you're dividing dowm to some other common frequency, you might be able to purchase a separate clock oscillator (which has the crystal, oscillator circuit and buffer built-in to provide a good HC-type output). If 48MHz is the ticket, you can get one from Jameco as their P/N 325738 for $1.35 USD, and it will plug directly into an 8-pin IC socket. Just supply +5V, and you're done.

formatting link

These ICs have higher drive capability than your uC output pin, and that might help.

Your problem also might be that you may be getting noise or reflections on the line going from your uC to the camera, or the trace inductance or capacitance between signal lines may be distorting your signal. If you're not using a PC board, keep the line as short and straight as possible. Look in the docs for the camera chip, and see if there's anything there about loading the signal.

Hope this helps. If not, feel free to post again and describe more about your problem.

Good luck Chris

Reply to
Chris

...

--- Yes. go to:

http://www:digikey.com

and enter "crystal oscillator" in the "Parts Search" box.

Then, when the next screen comes up, click on "Oscillators(3962 items)."

When the next screen comes up, scroll the "Frequency" column until you get to "48.000MHz", click on it, and then click on "Apply Filters".

On the next screen, click on "View Page" and then choose the oscillator you want from the 59 available.

Digi-Key has a better search engine than Mouser does, plus they have a "handling charge" if you don't order a $25 minimum, so once you find the oscillator you want, you might want to go to:

formatting link

and see if they have the same oscillator, since they don't have a minimum or a handling charge.

-- John Fields Professional Circuit Designer

Reply to
John Fields

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.