Idealy the spacing between the elements would be less than a wavelength and preferably 1/4 wavelength. With the wavelength being aprox 14mm it makes it very difficult to pack the ultrasonic cans close enough. The last array had relatively large spacing. A redesign packed the sensors as close as possible.

This array is still too limited to form arbitary beams. In combination with the already narrow beamwidth of the transducers, the side loves of the beam pattern formed by the array is suppressed. It might be possible to perform the scanning within a 30° range. Where only the main love is dominant. This is far from the original vision of a full >90° scan, but it's a start. It might be enough to work out the angle of the wall the sensor is looking at.

The ui on the pi has been developed to change a set of registers in the fpga. This has considerably sped up calibration of the array.