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Controlling a stepper motor through Mathematica

Posted 6 years ago
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Continuing with my stroll through the Adafruit Learning System, I set up a stepper motor with a ULN2803 according to lesson 10 and wrote some Mathematica code WolframLanguage code to control the stepper motor.  Below is a small package that does the trick.



 BeginPackage["gpiomotor`"]
 
 stepMotor::usage = "stepMotor[steps, direction, delay] where steps is an integer from 1 to 128, direction is 1 for forward and 0 for backward and delay is step time in ms (values less than 5 aren't meaningful).";
 motorRelease::usage = "motorRelease[] releases the coils so the motor does not draw current";
 
 $coila1pin = 4;
 $coila2pin = 17;
 $coilb1pin = 23;
 $coilb2pin = 24;

Begin["`Private`"]

$coils = {$coila1pin, $coila2pin, $coilb1pin, $coilb2pin};
$steps = {{1,0,1,0},{0,1,1,0},{0,1,0,1},{1,0,0,1}};

Clear[stepMotor]
stepMotor[steps_, direction_, delay_:5]:=Module[{dms,i},
dms = delay/1000;
For[i = 0, i < steps, i++,
  Map[(setStep[#];Pause[dms];)&,If[direction == 0, Reverse@$steps, $steps]]
  ]
]

Clear[motorRelease]
motorRelease[]:=Module[{},
setStep[{0,0,0,0}]
]

Clear[setStep]
setStep[array_]:=Module[{},
MapThread[DeviceWrite["GPIO",#1->#2];&,{$coils,array}];
]

End[]
EndPackage[]

Using Mathematica's `Map` function makes the code a little bit tighter than the corresponding tutorial python code.  As with my other discussion about `DeviceWrite`, it's quite slow, and you cannot currently set the delay to a small enough value to make the motor move smoothly.  However, using c/MathLink or `BinaryWrite` can improve the hardware interface access time much like other discussions presented in this forum.  I wanted to present a pure Mathematica solution here.
2 Replies
That's pretty cool! I haven't used motors a lot yet in my own experiments, but I think I will now.
Sorry for being late to the party. To reduce overhead, try using  DeviceWrite on a pre-discovered device, and once per array:
$gpio = DeviceOpen["GPIO"];

setStep[array_] := DeviceWrite[$gpio, Thread[$coils -> array]]
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