Gyro Drive on Spike Prime�using Python

spinny class

spinny class - implementation

• The Spinny class is an instance that allows you to run a motor to support an arm, lifter, or other spinny attachment.
• Funny name? Yes, it is silly, but I bet kids remember it!
• We used a class because it can be instantiated any number of times to support different spinny purposes.
• All versions have the same abilities, but a unique port ID and settings with their motor.
• To create a new version, you call the spinny with different parameters
• Our demos will use several examples
• The class is well documented
• It includes an enum, and functions all designed to move a motor.
• Their results are saved in a variable local to the instance. This way, they will not conflict with the ones for gyro_drive or other spinny instances.
• The spinny class code is heavily commented so we will only touch on the __init__, test and run methods parameters. Please walk the code with your kids so they get it.

Above we have 2 versions of spinny. This is a robot design available in the Spike Application. It has a front lifter and a back lifter.

spinny class – make me global

• Before you use your spinny handle, you must make it global.
• We make it global at the top of the main function because we are instantiating it in the main function.
• When created, the handle becomes global. (97)
• When we use it in code, if you see the red squiggles mocking you, it is either that your name is not global, not spelled correctly, or does not exist.

spinny class - parameters

• handle: Four character name of the instance. (required, used in logging. )
• port: hub motor port ( required, see motor )
• max_deg: +/-maximum degrees it will need to move. (required, always positive )
• max_vel: Motor max velocity. (enums, required)
• *accuracy: Degrees close to target to consider on target. (default 1, means -1,0,1)
• *stop_mode: State to leave motor in when we stop it?�(see motor, default motor.HOLD)
• *close_degrees: How close do we get before we slow down to hit target. (default: 60, improves accuracy)
• *close_speed: What speed to run at when close.�(default: 10)
• * Defaulted values: If you want to change them you need assign it with the variable name. �Note: The accuracy optional value is not changed. It is still defaulted to 1.

spinny class - __init__

• This is the class constructor.
• Notice: self is the first parameter. All class methods have this as the first parameter. It is a way of gathering all the class variables into a group called self. Google: python class self
• Review the code for what the parms do.
• Question: (218-225) Can you tell which are required and which are optional?
• In lines 227-234 we collect the incoming values and assign them to self variables. �Question: Some have the same names? �Why do they not conflict?
• At the bottom of __init__ we set a few values? Question: What are we doing?
• Hint, look at the code to figure it out.

spinny class - test

• This allows you to dial in your settings and experiment with your spinny.
• IMPORTANT: The first parameter is a list of integers you want to test.
• A list is entered as [value, value, value] or [ value ]. While this is not usually used, it can also be shown as list(value, value, value).
• We are using a list because this will allow you to test several positions to see how they interact.
• It will make students see a variety of variable types. Google: python list
• You need to start with the spinny in the starting position. In this case, that is down.
• With these settings you can to force the arm down.�You uncomment to use it. ��front_lift.test([-110], loops=1)�
• This will spin it down to the bottom. Be prepared to stop so you don’t strip your gears. Comment out when done.

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spinny class - test

• Parameters
• In your definition, you guess what the max degrees will be. In this case, we finally landed on 220°.
• All spinny class parameters are shown here so you can see and manipulate them.
• Start by uncommenting the return statement. This will force the program to terminate after the tests.
• Before you run any test, set the arm to the start position.
• To force the arm down you uncomment and use… �front_lift.test([-110], loops=1)�
• This will spin it down to the bottom. Be prepared to stop so you don’t strip your gears. Comment out when done.

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spinny class - test

• To run the test you populate the positions list.
• These are the positions [50,75,100,0] you want to try. You decide what you want to use based upon your design.
• The positions are percentages of the max_degrees. �So 50% is ½ of the range.
• Notice the last one is 0. This will force it to return to the start.
• Even though it may look like 90^o or 100^o, you have to remember there may be gears of different sizes involved.
• Run the test but be prepared to stop.
• ucomment and use

front_lift.test([50,75,100,0],

speed=20, loops=1)

• Once dialed in you use the max_degrees you figured out to set in the definition above.
• Position 100% should be your top most position.
• We tested our design the determined 220^o was the right value for the front lifter and 290^o for the rear one.

spinny class - testing

• What about the back lifter?
• In our design we want the the rear spinny all the way up to help us fit in the base at launch.
• We figured out the max_degrees as 290^o.
• We need to go negative to spin down. So all the positions are negative.

back lift.test([-50,-75,-100,0],

speed=20, loops=1)

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spinny class - testing

• We need to go negative to spin down

back lift.test([-50,-75,-100,0],

speed=100, loops=1)

• When running it will go fast until you are closer than close_degrees. Then it will use close_speed.
• We used speed100% just to see and it worked fine.
• The return is needed to stop after the test. �
• Remember when done testing you need to comment out these statements.

spinny class - run

• The run function moves the motor to the position% you requested.
• For this discussion we will assume…
• You are using the back_lift motor definition.
• At program start, you instantiate the class.
• The .reset() function is called. It resets the motor’s relative position to 0^o.
• For this reason arm must be in the full up position before you start the program.

spinny class - run

• These lines are what you could use to run the lift.
• At a minimum, you pass the position% and the speed%.
• The run function allows you to change some of the class variables on the fly temporarily.
• Just put a comma on the method parameter line. The UI will show the run options.
• The run method supports overrides for several variables. These are only changed for that call. They will not change the class settings.
• For example, you wanted to set close_degrees to 1^o on the last step so the lifter will move back up at full speed.
• We appended _override to help users better understand how it works. These are different variables.

Gyro Drive on Spike Prime�using Python

We invite you to walk the spinny code and learn. Google is very helpful.