Hello,
I am using the LM3s811 evalution kit, i am trying to achieve the speed > 6MHz for interfacing a camera for a project. I manage to get upto ~4Mhz using the PWM generator on PWM0 pin.
How can i get the frequency required on a GPIO pin ? Is it possible ? Can anyone please help me out ?
thanks!
--
Shanjit Singh Jajmann
Insufficient information to dig deep - really assist. A link to the camera spec would greatly help.
Direct Register Writes will increase GPIO toggle frequency - suspect that you need to receive (and assemble/store) camera data in sync with 6MHz clock. Check your MCU's SSI module - recall that it may operate beyond your 6MHz.
Lastly - what symptoms/issues result from your reduced, 4MHz clock. We've used "below spec" clocks and succeeded - may require buffering the data and this may/may not be suitable for your application.
Camera ID, data would be most helpful...
cb1- Insufficient information to dig deep - really assist. A link to the camera spec would greatly help.
The Camera i have,
http://electronics123.net/amazon/datasheet/AA5620.pdf
http://electronics123.net/amazon/datasheet/OV5620_CLCC_DS%20%281.3%29.pdf
cb1- Direct Register Writes will increase GPIO toggle frequency - suspect that you need to receive (and assemble/store) camera data in sync with 6MHz clock. Check your MCU's SSI module - recall that it may operate beyond your 6MHz.
I am intending to use the SD to store the image. Would be using the SPI bus there.
cb1- Lastly - what symptoms/issues result from your reduced, 4MHz clock. We've used "below spec" clocks and succeeded - may require buffering the data and this may/may not be suitable for your application.
didn't quite get this.
Many thanks for the quick reply!
Shan
Shanjit SinghLastly - what symptoms/issues result from your reduced, 4MHz clock.
I'm asking if you actually tried clocking the camera IC @ 4MHz - if so - what were your results? More than once we've seen clients do this and succeed. (often buffering the data before presenting for display and/or analysis)
If you did clock @ 4MHz and failed - describe in some detail what did not work - and how you made that measurement and judgement.
Have prior commitment now - tried to assist those I could in brief time/effort today - seek to respond to your issue late tonight. (USA - central)
cb1- Shanjit SinghLastly - what symptoms/issues result from your reduced, 4MHz clock. I'm asking if you actually tried clocking the camera IC @ 4MHz - if so - what were your results? More than once we've seen clients do this and succeed. (often buffering the data before presenting for display and/or analysis) If you did clock @ 4MHz and failed - describe in some detail what did not work - and how you made that measurement and judgement. Have prior commitment now - tried to assist those I could in brief time/effort today - seek to respond to your issue late tonight. (USA - central)
No i haven't tried that yet. I actually would be making a break out board for the camera, need to be sure of the pins first. Nevertheless i will give it a shot using individual jumper wires.
That camera IC is from a leader - Now - having had time to review the camera IC spec - hazard the guess that the Nobel committee would be @ your door-step if you can harness the OV5620 @ anywhere near full data rates with only a Cortex M3! (and a rather basic one at that) (Said M3 not equipped with CCP "compact camera port")
Looking at the chip's block diagram proves instructive - obliterates most all previously thought/posited... (diagram - please credit Omni Vision)
Note that only an "XVCLK" is input to this device - and this only when you want the camera IC to be "slave" to your master. (even that choice is fairly complex)
Here's the real "deal-breaker" - as concerns basic Stellaris (and other ARM MCUs) and this/other camera chips equipped with CCP:
TEN bits of parallel data are output by the camera IC with each clock - (2 lsb are thrown-away here.) How do you propose to first capture - then store this data with your M3 Stellaris - and be ready in time for the succession of high speed clocks and data which make up the camera frame? Clearly you'll need vast amounts of additional memory - along with the means to address, read/write, and strobe/control this added memory.
We've worked with far lesser camera chips - sense that this really is the province of an MCU which includes the CCP - your goal to "reinvent the wheel" may well be a misuse of time/effort/funds... (a good haunt of Omni-Vision site/forum (if any) probably provides deeper background than what my quick read of the 36 pg. datasheet revealed...
Hate to be "negative" - however find it doubtful that "faster toggling GPIO" (your Subject) will harness this camera chip - especially when dedicated CCPs are in existence. This may very well be the case when it's clearly best, "NOT to have invented here!" (NIH)
BTW - your post really did not center upon Fast Toggling GPIO - ask that you change post's Subject to, "performance camera chip interface" (or similar) as this seems far more appropriate... (and considerate of follow-on readers/searches)