Hi Zhaomin,
> Thank you very much for your interpretation.
> Now I meet with a new problem. After I reduce clock rate of CMOS
> sensor, I still cannot recognize each pixel value. Because the
> reading procedure seems not isochronous. Sometimes I read 638 data
> per line, sometimes 714 data per line. The extact pixel number should
> be 640 per line. Is it possible to make I/O speed isochronous?
You'd need to explain your CMOS interface.
If the sensor uses a read-control signal, and data
bits, and your controlling those, then all you'd have
to do is slow the sensor enough that you could read
640 times before the next frame.
However, if the sensor just writes out 640-samples at
a fixed clock rate, you'd be better writing some FPGA
code.
I haven't used the XDIO interfaces other than to test
toggle rates. Its possible there is a mode that you
can use them in, but I couldn't comment on it.
Given that you can slow the sensor down, the FPGA code would
be as simple as a FIFO. The sensor would write synchronously
to the FIFO, while the Linux code would read from it
(asynchronously). So long as the worst-case latency of
Linux is absorbed by the FIFO, you shouldn't lose any
data. If you're more adventurous, then have the FPGA
write to SDRAM, and then read from SDRAM.
I hope that gives you some ideas,
Dave
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