159 lines
3.9 KiB
Python
159 lines
3.9 KiB
Python
# SPDX-FileCopyrightText: 2018 Mikey Sklar for Adafruit Industries
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#
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# SPDX-License-Identifier: MIT
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"""
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This Code uses the:
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* Adafruit LCD backpack using MCP23008 I2C expander
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* Maxbotic LV-EZ1 Ultrasonic Sensor
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Tested with the Trinket M0
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The ultrasonic sensor and pin use should be Gemma M0 compatible
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This sketch reads the LV-EZ1 by pulse count
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Then prints the distance to the LCD and python console
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The circuit:
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* 5V to Trinket M0 USB or BAT pin, I2C Backpack 5V and EZ1 +5
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* GND to Trinket M0 GND pin, I2C Backpack GND and EZ1 GND
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* Display I2C Backpack SLK to Trinket GPIO #2
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* Display I2C backpack SDA to Trinket GPIO #0
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* LV-EZ1 Ultrasonic Sensor PW pin to Trinket GPIO #1
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* Backlight can be hard wired by connecting LCD pin 16, 17 or 18 to GND
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"""
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import time
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import adafruit_character_lcd
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import board
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import busio
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import pulseio
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ez1pin = board.D1 # Trinket GPIO #1
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# i2c LCD initialize bus and class
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i2c = busio.I2C(board.SCL, board.SDA)
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cols = 16
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rows = 2
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lcd = adafruit_character_lcd.Character_LCD_I2C(i2c, cols, rows)
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# calculated mode or median distance
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mode_result = 0
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# pulseio can store multiple pulses
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# read in time for pin to transition
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samples = 18
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pulses = pulseio.PulseIn(board.D1, maxlen=samples)
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# sensor reads which are in range will be stored here
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rangevalue = [0, 0, 0, 0, 0, 0, 0, 0, 0]
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# 25ms sensor power up pause
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time.sleep(.25)
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def tof_cm(time_of_flight):
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"""
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EZ1 ultrasonic sensor is measuring "time of flight"
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Converts time of flight into distance in centimeters
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"""
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convert_to_cm = 58
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cm = time_of_flight / convert_to_cm
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return cm
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def tof_inches(time_of_flight):
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"""
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EZ1 ultrasonic sensor is measuring "time of flight"
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Converts time of flight into distance in inches
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"""
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convert_to_inches = 147
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inches = time_of_flight / convert_to_inches
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return inches
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def find_mode(x):
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"""
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find the mode (most common value reported)
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will return median (center of sorted list)
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should mode not be found
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"""
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n = len(x)
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max_count = 0
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mode = 0
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bimodal = 0
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counter = 0
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index = 0
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while index < (n - 1):
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prev_count = counter
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counter = 0
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while (x[index]) == (x[index + 1]):
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counter += 1
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index += 1
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if (counter > prev_count) and (counter > max_count):
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mode = x[index]
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max_count = counter
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bimodal = 0
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if counter == 0:
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index += 1
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# If the dataset has 2 or more modes.
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if counter == max_count:
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bimodal = 1
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# Return the median if there is no mode.
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if (mode == 0) or (bimodal == 1):
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mode = x[int(n / 2)]
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return mode
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while True:
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# wait between samples
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time.sleep(.5)
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if len(pulses) == samples:
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j = 0 # rangevalue array counter
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# only save the values within range
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# range readings take 49mS
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# pulse width is .88mS to 37.5mS
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for i in range(0, samples):
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tof = pulses[i] # time of flight - PWM HIGH
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if 880 < tof < 37500:
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if j < len(rangevalue):
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rangevalue[j] = tof_cm(tof)
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j += 1
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# clear pulse samples
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pulses.clear() # clear all values in pulses[]
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# sort samples
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rangevalue = sorted(rangevalue)
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# returns mode or median
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mode_result = int(find_mode(rangevalue))
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# python console prints both centimeter and inches distance
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cm2in = .393701
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mode_result_in = mode_result * cm2in
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print(mode_result, "cm", "\t\t", int(mode_result_in), "in")
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# result must be in char/string format for LCD printing
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digit_string = str(mode_result)
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lcd.clear()
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lcd.message("Range: ") # write to LCD
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lcd.message(" ")
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lcd.message(digit_string)
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lcd.message("cm")
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time.sleep(2)
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