1-wire temperature graphing

Installing and Using OpenWrt
1

I wired up a DS18B20+ probe directly to GPIO4 on my Raspberry Pi 2 as per the following instructions: https://raspberrypi.stackexchange.com/a/48360

I then added OneWire support based on the following as well as installing kmod-w1, kmod-w1-gpio-custom, and their dependencies: https://learn.adafruit.com/adafruits-raspberry-pi-lesson-11-ds18b20-temperature-sensing/ds18b20

Now on to graphing.

I've had success with RRDTool in the past using these instructions based on Perl, however the collection method depends on the use of DigiTemp and unfortunately DigiTemp relies on a serial input device vs. direct GPIO access.

I tried the Python script supplied by Adafruit, and it worked well, however I'm not much of a programmer and would still need to learn how to output the results to RRD.

I then stumbled upon luci-app-statistics and found the collectd-mod-onewire plugin. It's an experimental plugin and marked broken in the OpenWrt makefile. I removed the @broken tag and it appeared to compile without issue for the x86_64 target. I tested this in Virtualbox, adding "--fake=10" to the owfs command, however could not get a proper plugin wrapper automatically written to /etc/collectd.conf from the luci-app-statistics UCI file.

I really like the idea of getting this working in luci-app-statistics if possible, but am definitely open to suggestions. Thanks!

2

I am late here, but very interested in how you compiled the plugin.
My device is a rpi3b+ and i would like to hook up 8x DS18S20 sensors and create a graph of them.
Can you tell me if it is possible to install that package on a raspberry somehow?
I doubt it is possible to build it on such a device...

3

Sorry for the late reply. It's been some time since I wrote this and I haven't kept up the config.

If you look at the Makefile that was available back then, you'll see where I edited out the @BROKEN flag.
$(eval $(call BuildPlugin,onewire,onewire sensor input,onewire,+PACKAGE_collectd-mod-onewire:libow-capi @BROKEN))

My guess is that that line as well as the following lines will need to be added back into the Makefile for compilation:

# exception: mod-onewire needs libow-capi
ifneq ($(CONFIG_PACKAGE_collectd-mod-onewire),)
  CONFIGURE_ARGS+= --with-libowcapi="$(STAGING_DIR)/usr"
endif

Here's the actual commit, where the code was removed:

4

Thanks a lot for replying.
Did you ever make it work?
I read the doc of collectd-mod-onewire and it seams to me as it can not attach local gpio, it might be designed to handle onewire adapters over serial or usb…

I am thinking of giving collectd-mod-exec a try and execute my python script reading exported gpio files directly like described in this german report…
But thats not really a nice solution in my eyes.

5

collectd-mod-onewire? No.

Thanks for jogging my memory. I'm pretty certain I ended up using collectd-mod-exec as well.

If I had to guess at the code I used in conjunction, it was probably a slight modification of the Adafruit Python code linked above to only output readings in Celsius.