raspi SerialException：设备报告已准备好读取但未返回任何数据。用于自动遥控车

Question

我一直在关注“使用 Raspberry Pi 和 Arduino 开始机器人学”一书，但遇到了代码问题。我对编程很陌生，并且正在使用这本书来熟悉 Pi、Arduino 和 Python。这本书有些含糊，没有提供解决问题的方法。

Traceback (most recent call last):
  File "/home/Danberry/Roject/pi_roamer_01.py", line 80, in <module>
    val = ser.readline().decode('utf-8')
  File "/home/Danberry/.local/lib/python2.7/site-packages/serial/serialposix.py", line 501, in read
    'device reports readiness to read but returned no data '
SerialException: device reports readiness to read but returned no data (device disconnected or multiple access on port?)

我已确认一切都已正确连接并且可以单独工作。现在的问题是让树莓派读取它。

import serial
import time
import random

from Adafruit_MotorHAT import Adafruit_MotorHAT as amhat
from Adafruit_MotorHAT import Adafruit_DCMotor as adamo

# create motor objects
motHAT = amhat(addr=0x60)
mot1 = motHAT.getMotor(1)
mot2 = motHAT.getMotor(2)
mot3 = motHAT.getMotor(3)
mot4 = motHAT.getMotor(4)

# open serial port
ser = serial.Serial('/dev/ttyACM0', 115200)

# create variables
# sensors
distMid = 0.0
distLeft = 0.0
distRight = 0.0

# motor multipliers
m1Mult = 1.0
m2Mult = 1.0
m3Mult = 1.0
m4Mult = 1.0

# distance threshold
distThresh = 12.0
distCutOff = 30.0

# speeds
speedDef = 200
leftSpeed = speedDef
rightSpeed = speedDef
turnTime = 1.0
defTime = 0.1
driveTime = defTime

def driveMotors(leftChnl = speedDef, rightChnl = speedDef, duration = defTime):
    # determine the speed of each motor by multiplying
    # the channel by the motors multiplier
    m1Speed = leftChnl * m1Mult
    m2Speed = leftChnl * m2Mult
    m3Speed = rightChnl * m3Mult
    m4Speed = rightChnl * m4Mult

    # set each motor speed. Since the speed can be a
    # negative number, we take the absolute value
    mot1.setSpeed(abs(int(m1Speed)))
    mot2.setSpeed(abs(int(m2Speed)))
    mot3.setSpeed(abs(int(m3Speed)))
    mot4.setSpeed(abs(int(m4Speed)))

    # run the motors. if the channel is negative, run
    # reverse. else run forward
    if(leftChnl < 0):
        mot1.run(amhat.BACKWARD)
        mot2.run(amhat.BACKWARD)
    else:
        mot1.run(amhat.FORWARD)
        mot2.run(amhat.FORWARD)

    if (rightChnl > 0):
        mot3.run(amhat.BACKWARD)
        mot4.run(amhat.BACKWARD)
    else:
        mot3.run(amhat.FORWARD)
        mot4.run(amhat.FORWARD)

    # wait for duration
    time.sleep(duration)

try:
    while 1:
        # read the serial port
        val = ser.readline().decode('utf=8')
        print val

        # parse the serial string
        parsed = val.split(',')
        parsed = [x.rstrip() for x in parsed]

        # only assign new values if there are
        # three or more available
        if(len(parsed)>2):
            distMid = float(parsed[0] + str(0))
            distLeft = float(parsed[1] + str(0))
            distRight = float(parsed[2] + str(0))

        # apply cutoff distance
        if(distMid > distCutOff):
            distMid = distCutOff
        if(distLeft > distCutOff):
            distLeft = distCutOff
        if(distRight > distCutOff):
            distRight = distCutOff

        # reset driveTime
        driveTime = defTime

        # if obstacle to left, steer right by increasing
        # leftSpeed and running rightSpeed negative defSpeed
        # if obstacle to right, steer to left by increasing
        # rightSpeed and running leftSpeed negative
        if(distLeft <= distThresh):
            leftSpeed = speedDef
            rightSpeed = -speedDef
        elif (distRight <= distThresh):
            leftSpeed = -speedDef
            rightSpeed = speedDef
        else:
            leftSpeed = speedDef
            rightSpeed = speedDef

        # if obstacle dead ahead, stop then turn toward most
        # open direction. if both directions open, turn random
        if(distMid <= distThresh):
            # stop
            leftSpeed = 0
            rightSpeed = 0
            driveMotors(leftSpeed, rightSpeed, 1)
            time.sleep(1)
            leftSpeed = -150
            rightSpeed = -150
            driveMotors(leftSpeed, rightSpeed, 1)
            # determine preferred direction. if distLeft >
            # distRight, turn left. if distRight > distLeft,
            # turn right. if equal, turn random
            dirPref = distRight - distLeft
            if(dirPref == 0):
                dirPref = random.random()
            if(dirPref < 0):
                leftSpeed = -speedDef
                rightSpeed = speedDef
            elif(dirPref > 0):
                leftSpeed = speedDef
                rightSpeed = -speedDef
            driveTime = turnTime

        # drive the motors
        driveMotors(leftSpeed, rightSpeed, driveTime)
        ser.flushInput()

except KeyboardInterrupt:
    mot1.run(amhat.RELEASE)
    mot2.run(amhat.RELEASE)
    mot3.run(amhat.RELEASE)
    mot4.run(amhat.RELEASE)

也许是某个地方的缩进问题？我已经玩了几个小时的代码，但还没有真正到达任何地方。如果你们中的任何人能提供帮助，那就太棒了！

Answer 1

听起来可能应该通过串行提供数据的任何东西都没有为您的程序提供足够频繁的数据。我很想抓住这个错误，然后再试一次（也许先等一会儿）。所以不是

try:
    while 1:
        # read the serial port
        val = ser.readline().decode('utf=8')
        print val

做

from time import sleep
...
try:
    while 1:
        # read the serial port
        try:
            val = ser.readline().decode('utf=8')
            print val
        except SerialException:
            sleep(0.01)  # Maybe don't do this, or mess around with the interval
            continue