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Stellaris launchpad clock output

cfny4g
Prodigy 155 points


Hi!

I'm trying to use my Stellaris launchpad with a camera module (OV7670). First of all I need to supply a clock for the camera, and its frequency must be between 8 and 40 MHz. 

Can I supply the clock from the launchpad or I need to build a clock generator circuit?

Sorry for my bad english :)

Thanks!

  • 0
    Guru 117855 points

    Unstated is any requirement for this "clock" signal to be synchronized to any other signal/bus/event.

    That said - use of any of the MCU Timers - configured for PWM Mode - enables easy and direct output from that timer's external pin.  Further - you can control both the frequency as well as the duty cycle of the output.  I believe that you can output up to 1/2 of the MCU's System Clock - via this method.

    MCU Datasheet will reveal which pins are timers - and provide reasonable set-up & config detail.   In addition "SW-DRL-UG" will list & detail various functions available to achieve your objective.

  • 0 in reply to cb1_mobile
    Prodigy 155 points

    Hi!

    Yes, I have tried this PWM method, but the result wasn't a square wave. I think I will build a circuit for that. Thanks!

  • 0 in reply to cfny4g
    Guru 117855 points

    G��bor K��rmendy said:
    but the result wasn't a square wave

    But it must be!  (and always has been such for our group.)

    Post your code - likely a failed SysCtlPeriphEn() which prevented a legitimate output. 

    Simply too easy for you to give up - expend needless effort - and produce something w/out the precision & flexibility of this powerful ARM feature...

  • 0 in reply to cb1_mobile
    Prodigy 155 points

    Hi!

    I did not give it up, but I thought the gpio port can't follow that 10-14 MHz frequency. Meanwhile I discovered that the cabel I used with the oscilloscope have too much capacitance. Because of that I can't see the square waves. 

    Thanks for helping.

  • 0 in reply to cfny4g
    Guru 117855 points

    Glad that you persisted - got it. 

    Always best to KISS - start at relatively low frequencies - confirm the basics - then gradually increase.