We have no problems running the motors from the documents you have provided after we calibrated them using a windows machine.
What we have not found are the flash addresses where the settings are (feedback max/min, max current, etc) and howto read/write directly to the flash (apply these new settings) using C/C++.
There sure is a .NET thing for linux but we do not favour it.
It would be great to have a document where all commands are explained.
Best regards and greetings from Vasa, Finland.
Patrik
Wow, that sounds like a very cool application of the jrk!
The jrk’s parameters are actually stored in EEPROM, not Flash. They can be set 1 or 2 bytes at a time using the Set Parameter USB control transfer. You can find the addresses of all the parameters in the jrkParameter enum in the file Jrk/protocol.h (or Jrk/Jrk/Jrk_protocol.cs) in the Pololu USB SDK. The Pololu USB SDK contains the source code for JrkCmd, a .NET command-line utility for the jrk that supports configuring the jrk. It uses libusb to do the USB communication. You can use libusb in your C++ program to do the same thing. We don’t have a document explaining how to do it, but what you can do is read the source code of the relevant part of JrkCmd and then implement the same thing in your C++ program. The relevant code starts in Jrk/JrkCmd/JrkCmd.cs, which calls some function in other parts of the SDK to do the real work:
if (opts.ContainsKey("configure"))
{
string filename = opts["configure"];
Stream stream = File.Open(filename, FileMode.Open);
StreamReader sr = new StreamReader(stream);
ConfigurationFile.load(sr, jrk);
sr.Close();
stream.Close();
jrk.reinitialize();
}
Using libusb is the way to go if you need to access parameters and configure it.
There is a work in progress Qt linux software at github for those interested https://github.com/poes-weather/Sensor-Benchmark
Here is a video of the proto Jrk rotor. 12v12 is used for elevation and 21v3 for azimuth.
Dish size 2.4 m, 50:1 gearboxes, 12 VDC motors. http://www.youtube.com/watch?v=hW8OwwpqeqU
As feedback sensors we use multiturn POT’s. Our target is to swing the dish with accuracy < 0.1 degrees.
Q: Would you recommend us to use a digital sensor (frequency/tachometer) to get “better” accuracy? If so, could you suggest us a link to such sensor.
This sensor doesn’t quite get you to your <0.1° accuracy, but it might get you closer:
They claim <0.5° accuracy under ideal mounting conditions (and at a fixed temperature). We have an alternate version of the jrk firmware that lets it work with this sensor.
Note that 0.1° resolution over a full 360° is very close to the theoretical limit of what the jrk can do, so I’m not sure if your goal will actually be achievable.