Serial example: Python : Processing data

[Maciek Wąchalski]

Hi,

I'm doing some tests with arduino connected to raspberry and using serial examples.

One of them is Python -Porocessing data.

I uploaded arduino sketch and did config on raspberry side.

When it runs for some time i get this error from time to time:

Exception in thread Thread-1:

Traceback (most recent call last):

  File "/usr/lib/python3.2/threading.py", line 740, in _bootstrap_inner

    self.run()

  File "/usr/local/lib/python3.2/dist-packages/WebIOPi-0.6.2-py3.2-linux-armv6l.                 egg/webiopi/utils/thread.py", line 23, in run

    self.func()

  File "/home/pi/Domeq/python/script3.py", line 27, in loop

    value = int(cv[1])

IndexError: list index out of range

then on the serial monitor i get:

2=267

3=263

4=252

5=246

46

1=252

2=263

3=258

4=246

5=240

2

4=241

5=236

Looks like some times data from arduino is not as expected (X=Y).

I'm not sure if it's arduino or webiopi side?

[Eric PTAK]

Is your serial monitor running when you got the error ?

Or do you launch the serial monitor after the error ?

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[Maciek Wąchalski]

It is running in browser window.

[Eric PTAK]

From https://code.google.com/p/webiopi/wiki/Tutorial_Serial#With_REST_mapping

"Be careful when using the REST API (with the Serial monitor) as well as using it from a custom script, you may notice strange behavior if you read data in your script. When data is received, it can be read only once."

When you make a script that poll Serial, you CAN'T use Serial Monitor.

[Eric PTAK]

There is also another note 

From https://code.google.com/p/webiopi/wiki/Tutorial_Serial#Python_:_Processing_data

"Instead of using Javascript Serial library, I prefer consume Arduino data directly on the server side, within a custom script, and provide a macro to ease UI interfacing. Disable Serial REST mapping by commenting or removing Serial setup from /etc/webiopi/config"

[Maciek Wąchalski]

Thanks, i'll 

Disable Serial REST mapping by commenting or removing Serial setup from /etc/webiopi/config"

and give it some more testing.

[Maciek Wąchalski]

Sometimes after first run:  webiopi -d -c /etc/webiopi/config

I get:

Exception in thread Thread-1:

Traceback (most recent call last):

  File "/usr/lib/python3.2/threading.py", line 740, in _bootstrap_inner

    self.run()

  File "/usr/local/lib/python3.2/dist-packages/WebIOPi-0.6.2-py3.2-linux-armv6l.egg/         webiopi/utils/thread.py", line 23, in run

    self.func()

  File "/home/pi/Domeq/python/script3.py", line 26, in loop

    channel = int(cv[0])

ValueError: invalid literal for int() with base 10: ''

does it have something to do with #empty input buffer before starting processing

in serial py examle?

[Maciek Wąchalski]

Looks like adding delay resolves this problem:

def loop():

    if (serial.available() > 0):

        webiopi.sleep(0.1)

        data = serial.readString()     # read available data

[Eric PTAK]

hum, ok, thanks !

[praveen kumar]

Hi Trouch,

                  i am running the sample processing that u have given for four sensors.i  made a custom script,when i compile it i got the following error..

pi@raspberrypi ~ $ sudo webiopi -d -c /etc/webiopi/config

2014-02-22 09:02:20 - WebIOPi - INFO - Starting WebIOPi/0.6.0/Python3.2

2014-02-22 09:02:20 - WebIOPi - DEBUG - Mapping GPIO.digitalCount to REST GET /GPIO/count

2014-02-22 09:02:20 - WebIOPi - DEBUG - Mapping GPIO.digitalRead to REST GET /GPIO/%(channel)d/value

2014-02-22 09:02:20 - WebIOPi - DEBUG - Mapping GPIO.digitalWrite to REST POST /GPIO/%(channel)d/value/%(value)d

2014-02-22 09:02:20 - WebIOPi - DEBUG - Mapping GPIO.getFunctionString to REST GET /GPIO/%(channel)d/function

2014-02-22 09:02:20 - WebIOPi - DEBUG - Mapping GPIO.getPulse to REST GET /GPIO/%(channel)d/pulse

2014-02-22 09:02:20 - WebIOPi - DEBUG - Mapping GPIO.outputSequence to REST POST /GPIO/%(channel)d/sequence/%(args)s

2014-02-22 09:02:20 - WebIOPi - DEBUG - Mapping GPIO.portRead to REST GET /GPIO/*/integer

2014-02-22 09:02:20 - WebIOPi - DEBUG - Mapping GPIO.portWrite to REST POST /GPIO/*/integer/%(value)d

2014-02-22 09:02:20 - WebIOPi - DEBUG - Mapping GPIO.pulse to REST POST /GPIO/%(channel)d/pulse/

2014-02-22 09:02:20 - WebIOPi - DEBUG - Mapping GPIO.pulseAngle to REST POST /GPIO/%(channel)d/pulseAngle/%(value)f

2014-02-22 09:02:20 - WebIOPi - DEBUG - Mapping GPIO.pulseRatio to REST POST /GPIO/%(channel)d/pulseRatio/%(value)f

2014-02-22 09:02:20 - WebIOPi - DEBUG - Mapping GPIO.setFunctionString to REST POST /GPIO/%(channel)d/function/%(value)s

2014-02-22 09:02:20 - WebIOPi - DEBUG - Mapping GPIO.wildcard to REST GET /GPIO/*

2014-02-22 09:02:20 - WebIOPi - INFO - GPIO - Native mapped to REST API /GPIO

2014-02-22 09:02:20 - WebIOPi - INFO - Loading configuration from /etc/webiopi/config

2014-02-22 09:02:20 - WebIOPi - INFO - Loading myscript from /home/pi/customscript.py

2014-02-22 09:02:20 - WebIOPi - ERROR - 'Serial' object has no attribute 'readString'

Traceback (most recent call last):

  File "/usr/local/lib/python3.2/dist-packages/WebIOPi-0.6.0-py3.2-linux-armv6l.egg/webiopi/__main__.py", line 73, in <module>

    main(sys.argv)

  File "/usr/local/lib/python3.2/dist-packages/WebIOPi-0.6.0-py3.2-linux-armv6l.egg/webiopi/__main__.py", line 67, in main

    server = Server(port=port, configfile=configfile)

  File "/usr/local/lib/python3.2/dist-packages/WebIOPi-0.6.0-py3.2-linux-armv6l.egg/webiopi/server.py", line 86, in __init__

    loadScript(name, source, self.restHandler)

  File "/usr/local/lib/python3.2/dist-packages/WebIOPi-0.6.0-py3.2-linux-armv6l.egg/webiopi/utils.py", line 168, in loadScript

    script.setup()

  File "/home/pi/customscript.py", line 13, in setup

    serial.readString()

AttributeError: 'Serial' object has no attribute 'readString'

pi@raspberrypi ~ $

Note:I had serial library for raspberry pi.

Awaiting for your valuable reply

regards,

Praveen Kumar

[Eric PTAK]

On the wiki, serial tutorial, prerequisites :

You will need to use the latest trunk from the SVN repository. There is a bug in the 0.6 release avoiding low-level binary interfacing. It has been fixed by r1368.

-- Eric/trouch

http://code.google.com/p/webiopi/

[pabs...@gmail.com]

i have same problem with webiopi serial streaming of arduino to raspberry pi,,it give me a error : File "/home/pi/serial/python/script3.py", line 26, in loop

    channel = int(cv[0])

ValueError: invalid literal for int() with base 10: ''

please help me,

[pabs...@gmail.com]

i already add webiopi.sleep(0.1) in python script but gives me same error

[Pete Dudash]

This error message tells you what is wrong. Changing the sleep time won’t help, but you already know that.

ValueError: invalid literal for int() with base 10: ''

What data type is stored in cv[0]? If it is a float or an empty string, then int() won’t work and you get the same error. If it is a string representing a decimal, try converting that first:

channel = int(float(cv[0]))

​

On Tue, Sep 15, 2015 at 9:27 AM, <pabs...@gmail.com> wrote:

i already add webiopi.sleep(0.1) in python script but gives me same error

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[pabs...@gmail.com]

thank you sir Pete Dudash,,

[pabs...@gmail.com]

error again, help please this is my code: 

 import webiopi

# import Serial driver

from webiopi.devices.serial import Serial

# initialize Serial driver

serial = Serial('/dev/ttyUSB0', 9600)

sensors = [0 for a in range(6)]

def setup():

    # empty input buffer before starting processing

    while (serial.available() > 0):

        serial.readString()

def loop():

    if (serial.available() > 0):

        data = serial.readString()     # read available data

        lines = data.split("\r\n")     # split lines

        count = len(lines)             # count lines

        lines = lines[0:count-1]       # remove last item from split which is empty

        # process each complete line

        for pair in lines:

            cv = pair.split("=")       # split channel/value

            channel = int(float(cv[0]))

            value = int(cv[1])

            sensors[int(channel)] = value   # store value

    webiopi.sleep(1)

# this macro scales sensor value and returns it as percent string

@webiopi.macro

def getSensor(channel):

    global result

    percent = sensors[int(channel)]

    return "%.1f" % percent

[pabs...@gmail.com]

line 28, in loop

   value = int(cv[1])