servo_demo Namespace Reference

Documentation for the servo_demo.py script. More...

Functions
def	connect (port)
	Sets the global ser variable. More...
def	sweep (initial, servos, starts, ends, steps)
	Produces complex command chains. More...
def	unsweep (servos, ends, steps)
	Produces a command chain that resets all servos to 0. More...
def	servowrite (commands, delay)
	Writes commands to the serial port. More...
def	gesture (initial, servos, starts, ends, steps, delay)
	Sets the servos to a position, waits for input, then resets them to 0. More...
def	reset ()
	Immediately sets the servos to 0. More...
def	cmd ()
	Sends the input to the serial port until a blank line is given. More...
def	dump (servos=6)
	Retrieves information about the board. More...
def	peace (delay=0)
	Makes a peace sign. More...
def	ok (delay=0.01)
	Makes an ok sign. More...
def	grab (delay=0.02)
	Makes a fist. More...
def	rockon (delay=0.01)
	Makes a rock on sign. More...
def	wiggle (n=90, delay=0.01, wiggles=1)
	Wiggles the fingers. More...
def	count ()
	Counts to 5 on the fingers. More...
def	demo ()
	Performs all movements. More...
def	getarrow ()
def	calibrate (s=1)
	Calibrate a servo. More...
def	calibrate_all ()

Variables
int	CANCEL_SIGNAL = 255
int	DUMP_SIGNAL = 253
int	START_RESPONSE = 252
int	END_RESPONSE = 251
int	RHAND_ID = 181
	The identification byte of the right hand board.
	ser = serial.Serial()
	The serial connection for input and output. More...

Detailed Description

Documentation for the servo_demo.py script.

An example script for controlling the right hand. This script can also be used to calibrate the bot. Please see connect, cmd, and calibrate. This script requires python with a library called pyserial. After instally python 3, pyserial can be installed by calling

pip install pyserial

Or through your package manager. Example:

sudo apt-get install python-pyserial

Once you have the library installed, you must have your PYTHONPATH variable set to the location of the library.

export PYTHONPATH=/usr/lib/python2.7/site-packages

Replace 2.7 with your version of python (type in /usr/lib/python and press tab once or twice).

This may vary from system to system. See the python and pyserial websites for help.

To run the script, execute

python -i servo_demo.py

or in python

import servo_demo

This will allow you to call the functions from a command interpreter. It is recommended you experiment with all functions and view the source to understand how you might produce commands. Also try demo() while connected.

The movements included are quickly written and for demo purposes only.

See also

Introduction for the servo codes.

Function Documentation

def servo_demo.calibrate

(

s = 1

)

Calibrate a servo.

Takes one argument, which is the id of a server. Introduction has the servo codes.

Use the left and right arrow keys to adjust the value of the servo. Use any other key to exit.

Enter the maximum values into the limit array in your settings file.

Note that if a servo isn't moving the correct way, for example if a finger isn't flat at 0 and curved at 180, you must set reverse to 1 at the servo index.

Definition at line 375 of file servo_demo.py.

def servo_demo.cmd

(

)

Sends the input to the serial port until a blank line is given.

Must enter integers between 0-255.

See also

Arduino Protocol

Definition at line 229 of file servo_demo.py.

def servo_demo.connect

(

port

)

Sets the global ser variable.

Call this to connect to the board.

connect ('/dev/ttyUSB0')

Replace /dev/ttyUSB0 with the name of the port your board is connected to. Usually this is /dev/ttyUSB* for the arduino nano or /dev/ttyACM* for the arduino uno. This is the same port used in Installation.

Note that you must be part of the dialout group in Linux. Enter this command to add yourself to a group.

usermod -a -G dialout $USER

You must logout to apply group changes. If you cannot logout, you can run the script as root.

sudo su
export PYTHONPATH=/usr/lib/python2.7/site-packages
python -i example/servo_demo.py

Definition at line 72 of file servo_demo.py.

def servo_demo.count

(

)

Counts to 5 on the fingers.

See also

sweep()

Definition at line 321 of file servo_demo.py.

def servo_demo.demo

(

)

Performs all movements.

Definition at line 329 of file servo_demo.py.

def servo_demo.dump

(

servos = 6

)

Retrieves information about the board.

The command sends the DUMP_SIGNAL to the serial port and reads back the response. The response is described in servo.ino.

When you write your own similar function, timing is important.

We may need to increase the response delay on the Arduino if you are unable to recieve a response. View the source of this function to understand how it works, but keep in mind it is untested. Also keep in mind that the function is very non-general as it always reads the same amount of bytes instead of looking for the end signal.

Note

While this function could be used to change dynamically between gestures instead of resetting the servos to 0, this function did not exist when this script was first written.

Definition at line 241 of file servo_demo.py.

def servo_demo.gesture	(		initial,
			servos,
			starts,
			ends,
			steps,
			delay
	)

Sets the servos to a position, waits for input, then resets them to 0.

See also

sweep() servowrite()

Definition at line 212 of file servo_demo.py.

def servo_demo.grab

(

delay = 0.02

)

Makes a fist.

See also

gesture()

Definition at line 295 of file servo_demo.py.

def servo_demo.ok

(

delay = 0.01

)

Makes an ok sign.

See also

gesture()

Definition at line 291 of file servo_demo.py.

def servo_demo.peace

(

delay = 0

)

Makes a peace sign.

See also

gesture()

Definition at line 287 of file servo_demo.py.

def servo_demo.reset

(

)

Immediately sets the servos to 0.

Definition at line 225 of file servo_demo.py.

def servo_demo.rockon

(

delay = 0.01

)

Makes a rock on sign.

See also

gesture()

Definition at line 299 of file servo_demo.py.

def servo_demo.servowrite	(		commands,
			delay
	)

Writes commands to the serial port.

If delay is 0, immediately writes a list of ints to ser as bytes. Otherwise, writes a list of ints to ser as bytes one at a time.

Inserting a delay controls the speed of the movements.

See also

connect()

Definition at line 195 of file servo_demo.py.

def servo_demo.sweep	(		initial,
			servos,
			starts,
			ends,
			steps
	)

Produces complex command chains.

The output returned from the function is formatted in such a way that the commands can be transmitted to the serial port at variable speeds.

The parameters must all be lists of the same length whose indexes correspond with servos.

Parameters

initial	An array of initial commands to append to.
servos	The servos to control.
starts	The current positions of the servos.
ends	The desired end positions.
steps	The values to use to decrement/increment. Converted to absolute value.

Returns

Upon success, returns the generated list of commands. The commands are surrounded by the CANCEL_SIGNAL for syncing. The servos will always reach their exact final destination, unless if steps at the index of the servo is 0. Upon error, raises 'Invalid sweep command'. This indicates non-matching list lengths.

Example

sweep ([], [1,2], [180,0], [90,180], [90,45]) 

Returns

[CANCEL_SIGNAL, 1, 180, 2, 0, 1, 90, 2, 45, 2, 90, 2, 135, 2, 180, CANCEL_SIGNAL]

The protocol this follows is described in servo.ino. By intertwining commands in this way, a delay can be inserted between bytes and fluid motion is still preserved.

Definition at line 103 of file servo_demo.py.

def servo_demo.unsweep	(		servos,
			ends,
			steps
	)

Produces a command chain that resets all servos to 0.

See also

sweep()

Definition at line 187 of file servo_demo.py.

def servo_demo.wiggle	(		n = 90,
			delay = 0.01,
			wiggles = 1
	)

Wiggles the fingers.

See also

sweep()

Definition at line 303 of file servo_demo.py.

Variable Documentation

servo_demo.ser = serial.Serial()

The serial connection for input and output.

Must be initialized.

See also

connect()

Definition at line 70 of file servo_demo.py.