weewx-cmon doesn't read cpu_temp of Raspberri PI

[Luc Heijst]

Recently I downloaded the latest version of weewx-cmon (v 0.20) which was converted to use with python3.

This version, and also elder versions of cmon.py, did not read the cpu-temp of my Raspberri PI systems (models 1B, 2B, 3B and 3B+).

On my raspberry PI the following statement is true: os.path.exists(tdir), still a cpu-temp could not be found in this section

The elif os.path.exists(tfile): statement caused the bottem section to be skipped and that is the section that reads the RPI cpu-temp.

See the modifications in yellow which fixed this problem.

Luc

--- snipped of cmon.py ---

        # read cpu temperature

        tdir = '/sys/class/hwmon/hwmon0/device'

        # rpi keeps cpu temperature in a different location

        tfile = '/sys/class/thermal/thermal_zone0/temp'

        temp_found = False

        if os.path.exists(tdir):

            try:

                for f in os.listdir(tdir):

                    if f.endswith('_input'):

                        s = self._readproc_line(os.path.join(tdir, f))

                        if s and len(s):

                            temp_found = True

                            n = f.replace('_input', '')

                            t_C = int(s) / 1000 # degree C

                            record['cpu_' + n] = t_C

            except Exception as e:

                logdbg("read failed for %s: %s" % (tdir, e))

        ### elif os.path.exists(tfile):  ### original statement

        if not temp_found and os.path.exists(tfile):

            try:

                s = self._readproc_line(tfile)

                t_C = int(s) / 1000 # degree C

                record['cpu_temp'] = t_C

            except Exception as e:

                logdbg("read failed for %s: %s" % (tfile, e))

-----------

[Tom Keffer]

Looks simple enough, but cmon is not part of weewx. You should submit as a PR to weewx-cmon.

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[Mike Revitt]

I have this working on my Rasberry pi at https://weather.cougar.eu.com/telemetry.html and this is how I did it

in weewx.conf 

In
[Engine]
 [[Services]]

set

data_services = user.cputemp.AddCpuTemp

Then add this Python program to the bin user directory where your Rasberry Pi code is.

#    Copyright (c) 2009-2020 Mike Revitt

#    See the file LICENSE.txt for your rights.

"""Gets the CPU temperature on a Rasberry Pi"""

import  weewx

from    weewx.engine    import  StdService

from    gpiozero        import  CPUTemperature

class AddCpuTemp(StdService):

    def __init__(self, engine, config_dict):

      # Initialize my superclass first:

      super(AddCpuTemp, self).__init__(engine, config_dict)

      # Bind to any new archive record events:

      self.bind(weewx.NEW_ARCHIVE_RECORD, self.new_archive_record)

    def new_archive_record(self, event):

        cpu = CPUTemperature()

       

        if event.record['usUnits'] == weewx.US:

            event.record['extraTemp1'] = ( cpu.temperature * 1.8 ) + 32

        else:

            event.record['extraTemp1'] = cpu.temperature

You can then access the Rasberry Pi CPU temperature as the variable extraTemp1 from within your HTML files 

[steeple ian]

Works perfectly.

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[Mike Revitt]

Glad I could help

[Jonathan Zitelman]

Mike, I have updated my weewx.conf file.  Could you offer a little more clarification on the new file?  To confirm this is the /usr/bin directory?  Does the filename matter?

-Jonathan

[Kevin Chapman]

Ok,  I am not familiar with Python at all.  I managed to work through the instructions above and make the changes to my weewx.conf file and then create cputemp.py in my /usr/share/weewx/user directory.  This eliminated the errors in the my syslog.  I am not seeing the cpu temp on the charts.  How would I look up the variables in python to see if they are registering at all. 

[vince]

We'd have to see the code you're running to look at it in detail.

Where did you get 'cputemp.py' and how can we get a look at the exact version you're running ?

FWIW - you check the temperature on a pi by running "vcgencmd measure_temp" which reads the right thing under /proc and formats it for output

[Kevin Chapman]

So below is the code I used from Mike Revitt.  I have no idea if it comes from a package. I followed Mike’s instructions as well as I could.  He was not clear what to name it or where to put it.  I created the python script in the ‘user/share/weewx/user folder.  At first, I named it AddCpuTemp.py but that generated errors starting weewx.  Then I named it cputemp.py and the startup errors went away.  I hope that makes sense.  

On Thu, Nov 12, 2020 at 6:23 PM vince <vince...@gmail.com> wrote:

We'd have to see the code you're running to look at it in detail.

Where did you get 'cputemp.py' and how can we get a look at the exact version you're running ?

FWIW - you check the temperature on a pi by running "vcgencmd measure_temp" which reads the right thing under /proc and formats it for output

On Thursday, November 12, 2020 at 3:19:45 PM UTC-8 kdch...@gmail.com wrote:

Ok,  I am not familiar with Python at all.  I managed to work through the instructions above and make the changes to my weewx.conf file and then create cputemp.py in my /usr/share/weewx/user directory.  This eliminated the errors in the my syslog.  I am not seeing the cpu temp on the charts.  How would I look up the variables in python to see if they are registering at all. 

You can then access the Rasberry Pi CPU temperature as the variable extraTemp1 from within your HTML files 

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[vince]

I would look for values in extraTemp1 in your database, as it seems that's where the python code is putting it.

A query that would report the last 10 readings of this sorted with most recent at the top is:

    echo "select datetime(dateTime,'unixepoch','localtime'),dateTime,extraTemp1 from archive order by rowid desc limit 10;" | sqlite3 weewx.sdb

What this is doing is saying 'give me a human readable date+time, the dateTime element, and the extraTemp1 element' from the archive table in the weewx.sdb database...and reverse sort it, showing me the 10 most recent readings (whew).

The location of weewx.sdb differs depending on how you installed weewx and what os you are running.   See http://weewx.com/docs/usersguide.htm#Where_to_find_things for what's where in the various variants of operating systems etc.

[Kevin Chapman]

Ok cool. I’ll check the database. Thanks for taking the time explaining it. 

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[Mike Revitt]

Sorry it has taken so long to respond to this, but I have just finished documenting how I added the CPU Temperature to my website, this is all documented here https://www.cougar.eu.com/useful-guides/weewx-guides/rasberry-pi/read-cpu-temp.html

 

 

Mike Revitt

Database Migration Specialist – Database Freedom

Amazon Web Services

e: revi...@amazon.com | p: +44.7825.063.466| w:  aws.amazon.com

 

 

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[Kevin Chapman]

Thank you.  I will check it out. 

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[Graham Eddy]

an alternative to repurposing an existing data_type is to define an xtype (e.g. see https://github.com/g-eddy/weewx-vitalstats)

[Tom Keffer]

That's a novel use of xtypes, but I'm not sure it's always a good idea. In this case, I think you'd be better off simply adding the type to the LOOP packet or archive record. 

The intended purpose of xtypes is to calculate derived variables. It's entirely possible it could be called many times during a reporting cycle, depending on the template used. Something involving I/O could be very expensive.

Having said that, xtypes also do database accesses, which can also be very expensive, so my advice is inconsistent. So, not saying never do it, but think it through.

-tk

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[Graham Eddy]

hmm, the ‘novelty’ i think is having an xtype calculated with values from outside weewx (eg cpu temperature), and the expense of the calculation is not really at issue - though normally they would be light-weight in case they are used often (eg barometer)

architecturally anything external is supposed to brought into weewx via a service and made available via weewx packet. (the *providing* of an xtype is now positioned as a service, but the xtypes themselves are not.)

okay, i’ll recast my vitalstats from xtypes_service to data_service and not bypass the packets...

[Graham Eddy]

i forgot to acknowledge the design consideration you raised that by calculating value once and storing it in the packet, unlike an xtype it is not re-calculated each time it is referenced