kopia lustrzana https://github.com/pimoroni/pimoroni-pico
Merge pull request #923 from pimoroni/patch/inventor_encoders
Added example for reading speeds from Inventor 2040W's encoderstest/inventor_build
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a87d5581aa
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@ -4,6 +4,7 @@
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- [Read ADCs](#read-adcs)
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- [Read GPIOs](#read-gpios)
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- [Read Encoders](#read-encoders)
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- [Read Speeds](#read-speeds)
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- [LED Rainbow](#led-rainbow)
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- [Reset Inventor](#reset-inventor)
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- [Motor Examples](#motor-examples)
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@ -22,13 +23,14 @@
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- [Velocity Tuning](#velocity-tuning)
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- [Position on Velocity Tuning](#position-on-velocity-tuning)
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- [Servo Examples](#servo-examples)
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- [Single Servos](#single-servo)
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- [Single Servo](#single-servo)
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- [Multiple Servos](#multiple-servos)
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- [Simple Easing](#simple-easing)
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- [Servo Wave](#servo-wave)
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- [Calibration](#calibration)
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- [Audio Examples](#audio-examples)
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- [Tone Song](#tone-song)
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- [Motor Song](#motor-song)
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## Function Examples
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@ -50,6 +52,12 @@ Shows how to initialise and read the 6 GPIO headers of Inventor 2040 W.
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Demonstrates how to read the angles of Inventor 2040 W's two encoders.
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### Read Speeds
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[read_speeds.py](read_speeds.py)
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Demonstrates how to read the speeds of Inventor 2040 W's two encoders.
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### LED Rainbow
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[led_rainbow.py](led_rainbow.py)
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@ -0,0 +1,46 @@
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import time
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from inventor import Inventor2040W, NUM_MOTORS # , MOTOR_A, MOTOR_B
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# from pimoroni import REVERSED_DIR
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"""
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Demonstrates how to read the speeds of Inventor 2040 W's two encoders.
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Press "User" to exit the program.
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"""
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# Wheel friendly names
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NAMES = ["LEFT", "RIGHT"]
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# Constants
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GEAR_RATIO = 50 # The gear ratio of the motor
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SPEED = 1.0 # The speed to drive the motors at
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SLEEP = 0.1 # The time to sleep between each capture
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# Create a new Inventor2040W
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board = Inventor2040W(motor_gear_ratio=GEAR_RATIO)
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# Uncomment the below lines (and the top imports) to
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# reverse the counting direction of an encoder
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# encoders[MOTOR_A].direction(REVERSED_DIR)
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# encoders[MOTOR_B].direction(REVERSED_DIR)
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# Set both motors driving
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for motor in board.motors:
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motor.speed(SPEED)
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# Variables for storing encoder captures
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captures = [None] * NUM_MOTORS
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# Read the encoders until the user button is pressed
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while not board.switch_pressed():
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# Capture the state of all the encoders since the last capture, SLEEP seconds ago
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for i in range(NUM_MOTORS):
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captures[i] = board.encoders[i].capture()
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# Print out the speeds from each encoder
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for i in range(NUM_MOTORS):
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print(NAMES[i], "=", captures[i].revolutions_per_second, end=", ")
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print()
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time.sleep(SLEEP)
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@ -6,6 +6,7 @@ This library offers an `Encoder` class that uses Programmable IO (PIO) hardware
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## Table of Content
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- [Table of Content](#table-of-content)
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- [Encoder](#encoder)
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- [Getting Started](#getting-started)
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- [Count and Angle](#count-and-angle)
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@ -102,7 +103,22 @@ degrees_per_second
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radians_per_second
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```
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Internally `.capture()` does the same up-front reading of values but does so more optimally within the underlying C++ driver. As an added bonus, it calculates encoder speeds too, by using the captured `delta` along with timing information returned by the PIO, more accurately than estimating a speed from the `delta` alone.
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Internally `.capture()` does the same up-front reading of values but does so more optimally within the underlying C++ driver. It calculates encoder speeds too, by using the difference between the current `count` and the **last capture's** `count` (aka the `delta`), along with timing information returned by the PIO. This produces speed readings that are more accurate than estimating a speed from the `delta` alone.
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:information_source: **It is recommended to perform captures frequently and at a consistent rate.** If this is not possible for your project, consider performing a dummy capture at the start of the time window you actually wish to measure the encoder's speed over.
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```python
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# Perform a dummy capture to clear the encoder
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enc.capture()
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# Wait for the capture time to pass
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time.sleep(CAPTURE_TIME)
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# Perform a capture and read the measured speed
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capture = enc.capture()
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print("Speed =", capture.revolutions_per_second)
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```
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### State
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