how to increase the DMA buffer size?

[karthigkin]

Posted on June 19, 2015 at 13:56

hi ,now i am working with camera interface with stm32f40IG controller.already i capture the image by using OV9655 camera which code and hardware are provide by STM.the sample code  is for just capturing the images and display that images in TFT by using TFT GRAM.

but i want to receive that captured datas in particular buffer.i received only upto 120x160 pixel rate.but i want to receive 240x320 pixel rate. the images are captured by DMA buffer.actually the datas are received upto 120x160 buffer range.if i configured that buffer range above 120x160 pixel means the IAR compiler says following error,Error[Lp011]: section placement failed           unable to allocate space for sections/blocks with a total estimated minimum size of 0x11962f4 bytes in  <[0x20000000-0x2001ffff]> (total uncommitted space 0x20000).  i think this error was happened because of limited DMA buffer size.for increasing DMA buffer size what can i do?thanks by,karthi.

[Tesla DeLorean]

Posted on June 19, 2015 at 14:24

No it's saying you have 128KB of SRAM and you're trying to allocate 18MB of space.

The DMA controller is limited to 65535 transfers, of up to 32-bit width. You might be able to play games with double buffering.

[karthigkin]

Posted on June 20, 2015 at 05:45

thank you for this valuable information clive.

how can i activate the double buffer.if i use double buffer means what is the maximum DMA buffer size and you  says the DMA buffer size is limited to 65535 transfers but i set the buffer size is 121x161 means its also says the error.(121*161 = 19481).how it was happened?.pls explain.