OpenHab vs. FHEM

Hey guys,

first of all, I’m a big fan of OpenHab and I’m not planning to move to another platform.

But when googling for home automation solutions, I can see that most of the time people are using FHEM instead of OpenHab. I can’t understand why they are doing this. I love the way OpenHab works and that it offers a REST API that I can use for my own development. Also the FHEM UI looks like a website from the 90s.

But why is FHEM so popular?
Have you ever planned to move from OpenHab to FHEM?
Or are you actually coming from an FHEM setup?

I’m really looking forward to your views and opinions.



Some people just start with something and don’t want to change. I moved to OpenHab from MisterHouse, it did a better job with Insteon, but in all other areas OpenHab blew it away. However I had spent a LOT of time building around Misterhouse.

It can be hard to walk away from something you invested so much time and energy in.

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I started last year with FHEM, because the search results were on top :grinning:
I didn’t find the setup very easy and it does not support the variety of hardware.
So I changed to openhab and didn’t regret it: easy setup (when you know where to look and read) and it supports all the hardware I need …

I’m pretty sure I will stick with it.

I was using FHEM for a couple of years before I switched to openHAB this year. I knew openHAB before and I tried it more then once, but at the end I always struggled with connecting my hardware (CUL-USB, FS20, FHT, S300TH) to openHAB.
There were two reasons for staying with FHEM for so long: first its very lightweight, I was running it on an old Raspberry PI. Second: FHEM recognizes all my hardware on its own without complex configuration.
But I still “hate” perl and when it comes to rules in FHEM I was always struggling and therefore I didn’t have had many rules at the end.
Now I am running openHAB on a newer Raspberry PI 2, spent hours and hours finding out how to connect my hardware with many “helping hands” and now everything is fine :wink:
My wishlist for openHAB is better documentation (at least for rules) and something like an automatic hardware recognition.

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Re rules doc…please chime in on this topic…

which architecturally will be possible with openHAB2 (and is one of the design goals) as long as the binding supports this discovery mechanisms (which is unfortunately not (yet) the case for your preferred hardware …

There are a few things for which I use fhem
for enocean I use the learning mode to get the Id of my devices.
for my buderus burner fhem has a module for KM200 which odes not exist on openhab (any volunteers ?)

another advantage for fhem : it is eaiser to create a new gui/frontend over it.

fhem is also running better on a raspberry B, less memory used.

I use openhab for knx, mqtt, sonos and enocean devices.

Apart from the features, possibilities and supported hardware, the technology where your home automation will depend on and where you will be investing your time and effort in, is important to many people. Especially as a developer/contributor in a free or open source software community.

For me, the OpenHAB dependency on Java/Oracle was the number one reason to look into other projects like FHEM (Perl) and Home Assistant (Python). Both use technologies which align better with my needs and systems. Despite setting me back quite a bit feature-wise, compared to OpenHAB.


Different people, different needs :sunglasses:

I would agree that OpenHab looks nicer than fhem but unless I’ve missed something they seem to hit different sets with some overlap in the middle. To me, and I’m looking for a system, it looks like OpenHab supports primarily off-the-shelf solutions only. Fhem has modules such as I2C_MCP23008 I2C_MCP23017 which are interface extenders on I2C and give 8/16 gpio lines. Openhab doesn’t have low level features like this. On Openhab you could use exec if you were running on say a raspberry pi and linux and use the linux tools for manipulating the gpio or I2C. But in order to do something useful takes a bit of programming. On fhem, in the gui, after installing one of the I2C_MCP23… modules you can do “set mod1 PortA4 on” which sets PortA4 high on a device you’ve named mod1. So it seems to me that fhem covers low level stuff that hobbyists might make for themselves or make out of bought bits, as well as off the shelf, where as openhab seems only off the shelf.

I should add that I’m not a fhem user, yet. I’m trying it. fhem documentation is very poor if you want to code modules and as non-german speaker I’m even more at a disadvantage. And fhem could certainly do with a make-over. However, it’s just a web page so getting a nicer looks shouldn’t be that hard.

I don’t think that’s right. OpenHAB has a GPIO binding, and several other bindings that are specific to “maker” integrations running on Arduino or other DIY projects. This is in addition to “generic” bindings like http, exec, modbus, tcp, serial, and others, as well as commercial products like Z-Wave, KNX, Nest, etc. See the wiki for more. In total there are approximately 200 addons included with openHAB that address a wide range of technologies.

Maybe I’m mistaken but I can’t find any I2C binding for openhab. If you take something like raspberry pi, 2 of it’s gpio can be set to be I2C bus, which you then expand to as much i/o as you need. True the openhab has gpio binding but that will be just the pi on board gpio and that’s pretty trivial to work with exec anyway at least setting and reading.

I’m not sure about speed either. Looking at the Piface binding which uses spi (4 gpio pins) to expand gpio that seems to be doing UDP <-> SPI which seems quite a bit of overhead. I’m looking to use SPI as comms to my custom hardware (in order to leave I2C free for standard fhem modules). My solution is a command line program i.e. stdin->SPI->stdout which seems the obvious route for a perl program. I presume openhab uses UDP as it base bus which is why PiFace is doing this.

If you look at FHEM community, you will recognize strong german-speaking publicum. This is because FHEM was running natively on AVM Fritzbox Router - most popular DSL Router in Germany. It looks also that it works pretty well with Homematic - wireless protocol similar to Z-wave with much better pricing for hardware.
I think this is why it is so popular.