About DMA problem..please help me

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You could have a cache problem. The CPU could be reading its data cache instead of the buffer in memory.

Try to create a second pointer:

alt_u8 *uncached_buffer = alt_remap_uncached(buffer,DEPTH);

and when you print the contents of the buffer, read the data with uncached_buffer[x], and see if you have different results.

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alt_u8 *uncached_buffer = alt_remap_uncached(buffer,depth);

gave compile error : invalid conversion from `volatile void*' to `alt_8*'

so i change it to

volatile void * uncached_buffer = alt_remap_uncached(buffer,depth);

but now the "uncached_buffer" variable cannot be read.