encoder_04.Encoder_04 Class Reference

Class to represent encoder object to handle encoder functions. More...

Public Member Functions
def	__init__ (self, int channel, pyb.Pin pin1, pyb.Pin pin2, int sample_freq, int period=65535, int prescaler=1, bool flipVelDirection=False)
	Creates encoder object. More...
def	update (self)
	Saves encoder value. More...
def	get_position (self)
	Returns position in radians. More...
def	get_velocity (self)
	Returns angular velocity. More...
def	zero (self, position=0)
	Zeros the encoder. More...
def	get_delta (self)
	Returns the latest saved difference in position. More...

Public Attributes
	pin_1
	First encoder pin. More...
	pin_2
	Second encoder pin. More...
	encoder_timer
	Timer object. More...
	encoder_channel
	Channel object. More...
	delta_cutoff
	Cutoff for detecting rollover. More...
	period
	Encoder counter max. More...
	abs_position
	Encoder position. More...
	last_pos
	Last encoder position. More...
	prev_delta
	Change in position. More...

Detailed Description

Class to represent encoder object to handle encoder functions.

Class to represent an encoder connected to two pins on board. Pins and channels may be specified through init arguments, but the user must confirm that the desired Pin and channel combination are allowed by the hardware specifications.

At very high speeds, the counter may fill too much between updates for this driver to handle. The minimum update speed is given by

where ω is the motor speed, CPR is the number of ticks per revolution, and Δ is the rollover cutoff, 1/2 the 'period' from the init method.

Constructor & Destructor Documentation

__init__()

def encoder_04.Encoder_04.__init__	(		self,
		int	channel,
		pyb.Pin	pin1,
		pyb.Pin	pin2,
		int	sample_freq,
		int	period = 65535,
		int	prescaler = 1,
		bool	flipVelDirection = False
	)

Creates encoder object.

You must ensure you are using a valid combination of pins and timer, found in the STM32 documentation.

Parameters

channel	Which channel is used on the timer of choice. This is often simply 1.
pin1	The first of the encoder's data pins.
pin2	The second of the encoder's data pins.
period	The maximum number of ticks before rollover. By default, this is set to the maximum 16-bit number.
prescaler	How many encoder ticks before the clock triggers. Increasing this can reduce rollover error at high speeds.

Member Function Documentation

get_delta()

def encoder_04.Encoder_04.get_delta

(

self

)

Returns the latest saved difference in position.

Getting the delta can act as a velocity measurement when combined with the sample frequency.

get_position()

def encoder_04.Encoder_04.get_position

(

self

)

Returns position in radians.

Returns currently saved position of the encoder (in ticks) from self.abs_position.

get_velocity()

def encoder_04.Encoder_04.get_velocity

(

self

)

Returns angular velocity.

Returns current angular velocity from the saved delta.

update()

def encoder_04.Encoder_04.update

(

self

)

Saves encoder value.

Saves the current position of the encoder (in ticks) to self.abs_position. Will handle rollover in direction unless the encoder is spinning too quickly (see class description for details)

zero()

def encoder_04.Encoder_04.zero	(		self,
			position = 0
	)

Zeros the encoder.

Set the current absolute position to the value passed in; zero by default.

Parameters

position

The current absolute position is set to this value.

Member Data Documentation

abs_position

encoder_04.Encoder_04.abs_position

Encoder position.

Stores the position of the encoder (in ticks)

delta_cutoff

encoder_04.Encoder_04.delta_cutoff

Cutoff for detecting rollover.

Set to 1/2 the period.

encoder_channel

encoder_04.Encoder_04.encoder_channel

Channel object.

Holds the channel setup for the timer used in the encoder.

encoder_timer

encoder_04.Encoder_04.encoder_timer

Timer object.

Holds the timer setup for the timer used in the encoder

last_pos

encoder_04.Encoder_04.last_pos

Last encoder position.

Position of the encoder (in ticks) from the last update

period

encoder_04.Encoder_04.period

Encoder counter max.

The maximum number of ticks before rollover.

pin_1

encoder_04.Encoder_04.pin_1

First encoder pin.

Signal pin from the first of the two sensors on the encoder.

pin_2

encoder_04.Encoder_04.pin_2

Second encoder pin.

Signal pin from the second of the two sensors on the encoder.

prev_delta

encoder_04.Encoder_04.prev_delta

Change in position.

Difference (in ticks) since the last update

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

• ME305_code/Lab0x04/encoder_04.py