Lab0x02_encoder.Encoder Class Reference

Interface with quadrature encoders. More...

Public Member Functions
def	__init__ (self, chA_pin, chB_pin, timNum)
	Constructs an encoder object. More...
def	update (self)
	Updates encoder position and delta. More...
def	get_position (self)
	Returns encoder position. More...
def	zero (self)
	Resets the encoder position to zero. More...
def	get_delta (self)
	Returns encoder delta. More...

Public Attributes
	tim
	tim creates new timer object for storing the encoder position. More...
	ch1
	creates channel 1 and channel 2 objects connected to the two pins input in the init function More...
	ch2
	prevCount
	Sets base object of prevCount (previous position) to 0. More...
	position
	position is the absolute position of the encoder. More...
	count
	delta
	delta is the difference between the current and previous positions More...

Detailed Description

Interface with quadrature encoders.

When called, this class generates an encoder object and assigns the desired timer and pins to it such that the position and change in position since the last update of the encoder position can be determined and returned as outputs.

Constructor & Destructor Documentation

__init__()

def Lab0x02_encoder.Encoder.__init__	(		self,
			chA_pin,
			chB_pin,
			timNum
	)

Constructs an encoder object.

Upon calling the Encoder.py class, the init function will run automatically. To run properly, this requires three inputs to the Encoder.py class call. There are: one input for each of the desired pins you wish to associate with the two encoder sensor channels. Additionally, the timer number to be used for the encoder position count must be defined as the third input when calling this class. This function will then instanciate an encoder object with the above parameters.

Parameters

chA_pin	creates empty object for an input of pin position. In this case we are using PB6 on the nucleo
chB_pin	creates empty object for an input of pin position. In this case we are using PB7 on the nucleo
timNum	creates an empty object for input timer. We will be using timer 4

Member Function Documentation

get_delta()

def Lab0x02_encoder.Encoder.get_delta

(

self

)

Returns encoder delta.

if user asks for delta to be returned, this function will return delta value calculated from update funciton

Returns

The change in position of the encoder shaft between the two most recent updates

get_position()

def Lab0x02_encoder.Encoder.get_position

(

self

)

Returns encoder position.

If the user asks for the position, after position is calculated using update function, this function returns the calculated value

Returns

The position of the encoder shaft

update()

def Lab0x02_encoder.Encoder.update

(

self

)

Updates encoder position and delta.

When called, this function will read and update the variable containing the encoder position, as well as the delta value of the encoder. This delta value will be analyzed for magnitude and direction to determine whether an overflow or underflow in the encoder position count has occurred since the last update. In the event that the encoder position count has overflowed or underflowed, this update function will add or subtract the appropriate value from the encoder position count to reflect the true position of the encoder relative to its home position.

Parameters

self

zero()

def Lab0x02_encoder.Encoder.zero

(

self

)

Resets the encoder position to zero.

If user inputs the desire to reset the counter to zero, this function resets the encoder position to zero

Member Data Documentation

ch1

Lab0x02_encoder.Encoder.ch1

creates channel 1 and channel 2 objects connected to the two pins input in the init function

ch1 and ch2 correspond to the inputs that will cause the encoder position to increment. This uses ENC_AB configuration which puts the timer in encoder mode: The counter changes when CH1 or CH2 changes. The order in which they change determines whether the encoder position increments or decrements.

delta

Lab0x02_encoder.Encoder.delta

delta is the difference between the current and previous positions

delta is used to test whether the counter has overflowed or not. It represents the change in count since the last time update() was called

position

Lab0x02_encoder.Encoder.position

position is the absolute position of the encoder.

position is initially set to zero and will be updated when update() runs to reflect the absolute position of the encoder.

prevCount

Lab0x02_encoder.Encoder.prevCount

Sets base object of prevCount (previous position) to 0.

This will be used in further calculations of delta, change in encoder position since the last update() call.

tim

Lab0x02_encoder.Encoder.tim

tim creates new timer object for storing the encoder position.

Runs timer 4 on the nucleo with a period of 2^16-1 and a prescaler of 0

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The documentation for this class was generated from the following file:

• Lab 0x02/Lab0x02_encoder.py