Distance Sensor の使用は，以下に示すエラーを発生する。
"I2C bus lock up" の可能性も疑われないではないが，症状の重篤化が進行している点を鑑みれば，システム破壊が疑われてくる。
test.py
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<![CDATA[#!/usr/bin/env python
import gopigo3
from easygopigo3 import EasyGoPiGo3
from di_sensors.easy_distance_sensor import EasyDistanceSensor
from time import sleep
import sys
gpg = gopigo3.GoPiGo3()
egpg = EasyGoPiGo3()
# Servo
# The case the servo cable is connected to Servo2.
servo_n = gpg.SERVO_2
# Distance sensor faces the front when gpg.set_servo(servo_n, 1400)
servo_center = 1400
def servo_front():
gpg.set_servo(servo_n, servo_center)
# Distance Sensor
dist_sensor = EasyDistanceSensor()
#Distance from obstacle where the GoPiGo should stop : 30cm
distance_to_stop = 30
# Moving
# go forward 1sec
def go_fwd():
egpg.set_speed(100)
egpg.forward()
sleep(1)
egpg.stop()
# Exit
def destroy():
gpg.reset_all()
egpg.reset_all()
sys.exit()
#### The Program starts from here ###############
print("Press ENTER to start")
#Wait for input to start
input()
#Start moving
servo_front()
go_fwd()
try:
while True:
#Find the distance of the object in front
dist = dist_sensor.read()
sleep(1)
print("Dist:",dist,'cm')
#If the object is closer than distance_to_stop, stop the GoPiGo
if dist < distance_to_stop:
print("obstacle!")
egpg.stop()
destroy()
sys.exit()
else:
go_fwd()
# except the program gets interrupted by Ctrl+C on the keyboard.
except KeyboardInterrupt:
egpg.stop()
destroy()
]]>
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$ vi test.py
$ chmod +x test.py
実行すると，途中から "[Errno 5] Input/output error" が現れる。
このエラーが出ると，dist は 0 になり，よって "obstacle!" となってプログラムは終了する：
<![CDATA[$ ./test.py
Press ENTER to start
Dist: 178 cm
Dist: 167 cm
Dist: 161 cm
Dist: 155 cm
Dist: 148 cm
Dist: 140 cm
Dist: 133 cm
Dist: 124 cm
Dist: 117 cm
Dist: 110 cm
[Errno 5] Input/output error
Dist: 0 cm
obstacle!]]>
起動を繰り返すごとに，エラー発生が早くなる：
<![CDATA[$ ./test.py
Press ENTER to start
Dist: 173 cm
[Errno 5] Input/output error
Dist: 0 cm
obstacle!
]]>
そして，起動でつぎのエラーが返されるようになる：
<![CDATA[$ ./test.py
Traceback (most recent call last):
File "./obstacle_stop.py", line 8, in <module>
dist_sensor = EasyDistanceSensor()
File "/usr/local/lib/python3.7/dist-packages/DI_Sensors-1.0.0-py3.7.egg/di_sensors/easy_distance_sensor.py",
line 56, in __init__
File "/usr/local/lib/python3.7/dist-packages/DI_Sensors-1.0.0-py3.7.egg/di_sensors/distance_sensor.py", line 28,
in __init__
File "/usr/local/lib/python3.7/dist-packages/DI_Sensors-1.0.0-py3.7.egg/di_sensors/VL53L0X.py", line 126,
in __init__
File "/usr/local/lib/python3.7/dist-packages/Dexter_AutoDetection_and_I2C_Mutex-0.0.0-py3.7.egg/di_i2c.py",
line 220, in write_reg_8
File "/usr/local/lib/python3.7/dist-packages/Dexter_AutoDetection_and_I2C_Mutex-0.0.0-py3.7.egg/di_i2c.py",
line 185, in transfer
File "/usr/local/lib/python3.7/dist-packages/Dexter_AutoDetection_and_I2C_Mutex-0.0.0-py3.7.egg/di_i2c.py",
line 469, in transfer
OSError: [Errno 5] Input/output error]]>
このエラーは，EasyDistanceSensor() の呼び込みで起こっている：
<![CDATA[$ python
>>> from di_sensors.easy_distance_sensor import EasyDistanceSensor
>>>
>>> dist_sensor = EasyDistanceSensor()
Traceback (most recent call last):
File "./obstacle_stop.py", line 8, in <module>
dist_sensor = EasyDistanceSensor()
File "/usr/local/lib/python3.7/dist-packages/DI_Sensors-1.0.0-py3.7.egg/di_sensors/easy_distance_sensor.py",
line 56, in __init__
File "/usr/local/lib/python3.7/dist-packages/DI_Sensors-1.0.0-py3.7.egg/di_sensors/distance_sensor.py", line 28,
in __init__
File "/usr/local/lib/python3.7/dist-packages/DI_Sensors-1.0.0-py3.7.egg/di_sensors/VL53L0X.py", line 126,
in __init__
File "/usr/local/lib/python3.7/dist-packages/Dexter_AutoDetection_and_I2C_Mutex-0.0.0-py3.7.egg/di_i2c.py",
line 220, in write_reg_8
File "/usr/local/lib/python3.7/dist-packages/Dexter_AutoDetection_and_I2C_Mutex-0.0.0-py3.7.egg/di_i2c.py",
line 185, in transfer
File "/usr/local/lib/python3.7/dist-packages/Dexter_AutoDetection_and_I2C_Mutex-0.0.0-py3.7.egg/di_i2c.py",
line 469, in transfer
OSError: [Errno 5] Input/output error
>>> quit()
]]>
起動エラーの症状は，Raspberry Pi をパワーオフ・オンした後も残るようになる。
起動エラーが発生せずに起動しても，Distance Sensor がおかしい値を返してくるようになる：
<![CDATA[$ ./test.py
Press ENTER to start
Dist: 300 cm
Dist: 300 cm
Dist: 300 cm
[Errno 5] Input/output error
[Errno 5] Input/output error
[Errno 5] Input/output error
Dist: 0 cm
obstacle!]]>
症状は，プログラムの起動を重ねるほど，重篤化する。
Distance Sensor を呼び込むごとにシステム破壊が起こっており，システム破壊が進行するということである。
| 註. |
「Traceback (most recent call last)」に書かれているファイル/ディレクトリは，この通りの形では存在していない：
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<![CDATA[$ ls -la /usr/local/lib/python3/dist-packages
-rw-r--r-- 1 root staff 27098 Apr 7 14:35 Dexter_AutoDetection_and_I2C_Mutex-0.0.0-py3.7.egg
-rw-r--r-- 1 root staff 117346 Apr 7 13:03 DI_Sensors-1.0.0-py3.7.egg
$ ls -la /usr/local/lib/python3.7/dist-packages
-rw-r--r-- 1 root staff 117346 Apr 7 13:03 DI_Sensors-1.0.0-py3.7.egg]]>
<![CDATA[
$ find /usr -name easy_distance_sensor.py
(無し)
$ find /usr -name distance_sensor.py
(無し)
$ find /usr -name VL53L0X.py
(無し)
$ find /usr -name di_i2c.py
(無し)
$ find ~ -name easy_distance_sensor.py
/home/pi/Dexter/DI_Sensors/Python/di_sensors/easy_distance_sensor.py
$ find ~ -name distance_sensor.py
/home/pi/Dexter/DI_Sensors/Python/di_sensors/distance_sensor.py
$ find ~ -name VL53L0X.py
/home/pi/Dexter/DI_Sensors/Python/di_sensors/VL53L0X.py
$ find ~ -name di_i2c.py
/home/pi/Dexter/lib/Dexter/RFR_Tools/miscellaneous/di_i2c.py]]>
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"I2C bus lock up"