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adding inclinometer example #4

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Merged
merged 4 commits into from
Feb 7, 2020
Merged

adding inclinometer example #4

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d61a94d
adding inclinometer example
FoamyGuy Feb 5, 2020
b2fbce5
adding inclinometer example, change import order for pylint
FoamyGuy Feb 5, 2020
dcda6cc
refactoring and new string formatting
FoamyGuy Feb 6, 2020
4b2689e
more descriptive variable names for print statement
FoamyGuy Feb 7, 2020
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38 changes: 38 additions & 0 deletions examples/lsm303_accel_inclinometer.py
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Original file line number Diff line number Diff line change
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""" Display inclination data five times per second """

import time
from math import atan2, degrees
import board
import busio
import adafruit_lsm303_accel


i2c = busio.I2C(board.SCL, board.SDA)
sensor = adafruit_lsm303_accel.LSM303_Accel(i2c)


def vector_2_degrees(x, y):
radians = atan2(y, x)
degrees_calc = degrees(radians)
if degrees_calc < 0:
degrees_calc = 360 + degrees_calc
return degrees_calc
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Could be shortened to something like

angle = degrees(atan2(y, x))
if angle < 0:
    angle += 360
return angle

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Same here, will make this change tonight.



def get_inclination(_sensor):
return get_inclination_respect_x(_sensor), get_inclination_respect_y(_sensor)
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With this approach you read the sensor twice. It probably happens so fast it's no big deal. But you could get rid of the two get_inclination_respect functions and have this one be something like:

x, y, z = _sensor.acceleration
return vector_2_degrees(x, z), vector_2_degrees(y, z)

and then both inclination computations would be done from the same sensor reading.

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Thank you for pointing this out. Like you say it's so fast it usually doesn't matter but I have had the pleasure of debugging weirdness caused by making multiple reads like this getting different results on with other sensors, definitely should be storing it to a variable to reference from there instead. I will get this changed tonight as well.



def get_inclination_respect_x(_sensor):
accel_axis_data = _sensor.acceleration
return vector_2_degrees(accel_axis_data[0], accel_axis_data[2])


def get_inclination_respect_y(_sensor):
accel_axis_data = _sensor.acceleration
return vector_2_degrees(accel_axis_data[1], accel_axis_data[2])


while True:
print("inclination: (%s, %s)" % (get_inclination(sensor)))
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Consider switching to newer style .format string formatting instead of %.

Also maybe add more description of what the two values are? Something like this?

print("XZ angle = {:6.2}deg   YZ angle = {:6.2}deg".format(get_inclination(sensor)))

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I like it, will make this change tonight.

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I'm getting this error when I use this code as is.

TypeError: can't convert 'tuple' object to str implicitly

I've changed it to this which solves this tuple conversion error by making a variable and accessing the indexes individually. If there is some other syntax that allows it to work as a one liner I can use that but I'm not sure of how to do it. I also used float formatting because it showed exponential notation sometimes.

inclination = get_inclination(sensor)
print("XZ angle = {:6.2f}deg   YZ angle = {:6.2f}deg".format(inclination[0],inclination[1]))

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Ah, yah. My bad. I was just coding from the hip. The actual formatter syntax may be wrong too.

Try this:

print("XZ angle = {:6.2f}deg   YZ angle = {:6.2f}deg".format(*get_inclination(sensor)))

Added fs to the formatter and used the * trick to unpack the tuple. What do you think about splitting it into two lines?

angle_xz, angle_yz = get_inclination(sensor)
print("XZ angle = {:6.2f}deg   YZ angle = {:6.2f}deg".format(angle_xz, angle_yz))

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Ah the asterisk does work. I like your two line version best. I've just pushed a change to that one.

time.sleep(0.2)