I finally received the Moonlite focuser from the USA after a bit of a holdup in customs. It really does look like a decent (and heavy) piece of kit. The people who called it a work of art were only slightly exaggerating.

I soldered up a DB9 cable and crimped the 6p6c connector on the other end, plugged it in, booted the Pi and told it to move via the Ekos driver and….. nothing, other than a sinking feeling.

Debugging

Is it a problem with the high res motor? Cable? Controller? Driver? something else?

I was reasonably confident the outputs from the DRV8805 were valid based on prior testing which made the most likely candidate the driver, cable or focuser motor itself. Hooking the focuser motor up to a breadboard and manually applying 12v and GND to the coils showed signs of life, so the driver or cable…

The cable itself seemed to have good connections, which left the pinout.

After reviewing the DRV8805 datasheet and the Moonlite focuser stepping sequence diagram, the issue was clear. Output 1..4 on the DRV was a matching sequence for the Moonlite focuser but not with a direct Out1->In1..Out4->In4 connection. The final ordering was:

Pi Side	DB9 Side
12v	12v
Out1	O1
Out2	O4
Out3	O2
Out4	O3

With a small adjustment to the cable the focuser finally moved, in the wrong direction! The driver had the clockwise/counter clockwise mapping backwards. Thankfully, a trivial fix.

The driver GUI is nothing to write home about, but then ideally you won’t need to ever really use this part of INDI, all control should be possible via the regular EKOS GUI. With a couple of exceptions like enabling temperature compensation and initial centering of the focuser. It’s not pretty, but it should get the job done.

Almost there

With those minor issues out the way, everything seems to finally be working. I now have a way to control my CCD camera, guide cam, filter wheel, LX90 mount and the new focuser wirelessly via a raspberry PI attached to the side of the telescope. All that remains now is to add a socket to connect the DS18B20 temp sensor, update the driver to read it and automatically apply focus corrections as the temperature changes throughout the night.

First light for the focuser is still a little off as it’s quite heavy, adding about 4.5lbs to the rear of the scope. Additional counterweights are going to be needed before I can finally put this to use under the the stars. Lets hope it’s all been worth it.

I’ll end this post with an action packed, amazing, jaw dropping video of the focuser in action.

Yeah I lied, it’s a focuser moving, how exciting did you really expect that to be?

Source

The updated indilib driver, firmware and hardware schematic/layouts are available at: