Astrophotography - the mount driver

I am using an old Vixen GP mount with the Vixen MT1 stepper motors.

I am using a raspberry pi with Pololu stepper drivers. I've described this in an earlier post.

Now comes the job of making this work - initially for guiding and hopefully later for 'goto' as well (albeit that will be a bit slow with these motors).

The ingredients are:

1. pi model B
2. 2 pololu drivers mounted on a little HAT card as described here
3. a 24v power supply to drive the stepper motors
4. CAREFULLY set the current limit on the pololu driver carriers
5. write a test program to do some basic testing of the drivers / motors
6. Prepare a second raspberry pi to run this nice autoguiding software
7. do a quick hack to enable Gordon'd autogider software to talk to my driver software.

I have done a quick video of the test program running the code to slew the scope as fast as the steppers can go here.

and below is the gory details.....

I am running this on a pi model B......

1. started with clean install of jessie lite (2016-11-25-raspbian-jessie-lite.img)
2. usual new pi things like enable ssh, expand filesystem and setup nfs server
3. sudo apt-get install python3
4. setup pigpio as detailed here
5. and set it to start at raised priority automatically at boot:
   sudo crontab -e
6. add this to the end of the crontab file:
   @reboot              /usr/bin/nice -n -5 /usr/local/bin/pigpiod
7. link up to my file server
8. STILL *sigh* have to fix the rpcbind - nfs server screw up - from here

I run pigpiod at slightly raised priority as on the model B I am using I was getting occasional stutters of a millisecond or two in pigpio scripts that were enough to throw the stepper motors into freeze buz mode at high stepping rates.

That's the basic setup completed