Pcam Demo and VDMA

[MLee]

I was working with the Pcam demo on the zybo z7 10.

What addresses are the camera data stored to in DDR Memory? I want to pull the data from Vitis on the software side and do some processing/checking.

How many pixels are stored in one address? Does this depend on the resolution? For example, if I'm using a 720 x 1280 resolution are there 921600 addresses to read from for one picture?

I imagine the DDR addresses are rewritten over and over again. What's the best way of keeping the data before it is overwritten?

[elodg]

Base address for frame buffers defined here: https://github.com/Digilent/Zybo-Z7-SW/blob/f0965519d72cd14d039215ca6b35c885a71405df/src/Zybo-Z7-20-pcam-5c/src/main.cc#L25

Passed to AXI_VDMA constructor here: https://github.com/Digilent/Zybo-Z7-SW/blob/f0965519d72cd14d039215ca6b35c885a71405df/src/Zybo-Z7-20-pcam-5c/src/main.cc#L82

Frame addresses calculated for each buffer here: https://github.com/Digilent/Zybo-Z7-SW/blob/f0965519d72cd14d039215ca6b35c885a71405df/src/Zybo-Z7-20-pcam-5c/src/ov5640/AXI_VDMA.h#L158

You can get an interrupt when a complete frame is written: https://github.com/Digilent/Zybo-Z7-SW/blob/f0965519d72cd14d039215ca6b35c885a71405df/src/Zybo-Z7-20-pcam-5c/src/ov5640/AXI_VDMA.h#L232

Then either read is fast enough before the VDMA cycles through the other two buffers and begin overwriting the frame, or stop the pipeline until you can read out the frame.