For my unofficial entry into the Picasso Design Challenge I have made some progress and I now have three working wheel units. I weighed the few remaining centimetres of plastic filament that I had left for my 3D printer and discovered that I had just enough to print out the supports for one more of the step motor units, so I printed them out. There is now only 10 or 20 centimetres of filament left so not enough for the fourth wheel unit. However, I have ordered some more, which has to come from America to the UK, a bit expensive but it should be here by Friday and then I will be able to complete the motor units. The video below shows the HoloPiBot moving with three motor units and one support and it seems to be moving better and seems capable of continuing even when a greater weight is added. The HoloPiBot can also climb small obstacles, but only just. However, it will not have to overcome any obstacles when in final use as the surface will be completely flat.
I was also able to add my Raspberry Pi 3B+ which arrived recently, along with the camera. Unfortunately I do not think I will be able to use either of the cases that I now have (one came with the display and one came with the starter kit) as the PCB only just fits into the space, when the original holes in the acrylic display surround are used. As I do not want to drill anymore holes in the acrylic unless I really have to I will just do without the case. The Ethernet connector on the Raspberry Pi 3B+ is obscured but I will not be using it anyway, so no problem. All the other connectors seem accessible although it does look as if it will be tricky to get the memory card into it's slot.
At present the Raspberry Pi 3B+ is not working or connected as I still need to set it up. I just wanted to make sure it would fit into place.
I will now have to implement a method for connecting all eight of the step motor drive PCBs into the system. As all the motors will be operating in the same direction I am contemplating just using two step driver PCBs. One for the four drive wheels and another for the four direction motors. It will depend on whether the PCB can cope with the current for four step motors (I think it will) and whether the battery being used is able to provide the instantaneous current needed when four steps are taken at the same time.