I haven't looked at them for a long time but I think they are all from Hard Kernel Odriod-N2s and XU4s. Lost count of them but >16. Some are in their own rack cabinets. My son and I searched for a while then gave up looking for some way of daisy chaining them together. We consider Lego or Mechano parts but now they just dangle in the air loose in the rack cabinets (to try to minimise dust accumulating).