pynq.buffer Module

Home of the pynq.allocate function

class pynq.buffer.PynqBuffer

Bases: numpy.ndarray

A subclass of numpy.ndarray which is allocated using physically contiguous memory for use with DMA engines and hardware accelerators. As physically contiguous memory is a limited resource it is strongly recommended to free the underlying buffer with close when the buffer is no longer needed. Alternatively a with statement can be used to automatically free the memory at the end of the scope.

This class should not be constructed directly and instead created using pynq.allocate().

device_address

The physical address to the array

Type:int

coherent

Whether the buffer is coherent

Type:bool

cacheable

close()

Unused - for backwards compatibility only

flush()

Flush the underlying memory if necessary

freebuffer()

Free the underlying memory

This will free the memory regardless of whether other objects may still be using the buffer so ensure that no other references to the array exist prior to freeing.

invalidate()

Invalidate the underlying memory if necessary

physical_address

sync_from_device()

Copy the contents of the device buffer into the mirrored host buffer

sync_to_device()

Copy the contents of the host buffer into the mirrored device buffer

virtual_address

pynq.buffer.allocate(shape, dtype='u4', target=None, **kwargs)

Allocate a PYNQ buffer

This API mimics the numpy ndarray constructor with the following differences:

• The default dtype is 32-bit unsigned int rather than float
• A new target keyword parameter to determine where the buffer should be allocated

The target determines where the buffer gets allocated

• If None then the currently active device is used
• If a Device is specified then the main memory