I am running HA on HassOS on RPi 3B+ and for a start I would like to add room sensors for temperature and humidity. I ordered a bunch of BME280 breakout boards now I am wondering what to wire them to. For the first sensor is it possible to connect it to the RPi with HassOS? And for the rest, RPi zero, esp32 featherboards,…? I am guessing I need to install some client software on them?
In addition to sensors I would like to implement bluetooth scanning for room presence, add IR receiver&transmitter (mostly to control AC). Perhaps wire a few relays as well.
I can not recommend this highly enough:
Choose any ESP32 or ESP2866 board and from a very wide range of sensors (BME280 is there as is an IR receiver/transmitter and switch for your relays). All set up with a simple web browser interface and yaml. No reall coding involved at all.
Start by having a look at the getting started with Hassio page
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First step done, I have en esp32 board in every room with temp&humidity sensors, programmed and integrated into HA through ESPHome.
And the next problem, I would like to add more i2c sensors so I am looking for a splitter, like the one below, but with a more reasonable price, this one costs almost the same as an esp board…
Suggestions?
You can connect more than one sensor to the I2C bus. All you need to do is make sure that each sensor connected to the I2C bus has a different address. What sensors do you want to use for each esp?
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In the next step, a few esp boards will get an additional temp&humidity sensors (for outside), most will probably get a lux sensor.
Which BME280 breakout board are you using?
Most have address settings. Default is 0x77 otherwise 0x76. So you can use two per ESP board on the the same I2C pins without issue.
If you use a BH1750 board for the Lux sensor the address pin pulled high will give an address of 0x5C otherwise it’s the default 0x23, so that can be used on the same bus too.
Having said that I2C stands for IC to IC (i.e. on a circuit board between integrated circuits). It is not meant to be a long range communications bus (about 2m max at the lowest speed). So if you want one sensor inside and one outside you might be better off with additional ESP boards - depending on the lead length. The D1 mini’s are cheap.
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I am using this:
https://www.amazon.de/gp/product/B01GQ3T1A4/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1
Thanks for the lux board suggestion.
Yes, the addresses shouldn’t be a problem, what I am looking for is a simple “pin splitter” as I linked in the post above, so I can connect everything together, without splicing and soldering the wires.
Thanks for the info regarding cable length, 2m should be enough for my needs. Are there any recommended cables for i2c? I plan to use sftp cables.
No. The recommendation is not to take it off the board.
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This has some advice:
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I used cat5e sftp cable, approx 5m in length, one wire of each twisted pair for 3.3v, gnd, sda, sck and I also connected the shield to ground on esp32 side and i2c works 
hello peter
care so share some pics of this install?
How many sensors do you currently have on each board now
what are you using to power the chips ?
thanks
Sorry for late reply… I don’t have pics, its a ghetto install, no cases, a mess of wires, nothing to be proud of, really
I have one esp32 per room, powered by a mobile phone charger. Number of sensors connected vary, mostly one bme280 and one bh1750 with short “jump wires”; in two rooms I have 2 bme280 sensors connected to the esp32 board, second being used to measure outdoor temperature connected with 5m sftp cable; I also have a couple of dallas temperature sensors and a few relays for switching various things.
A bunch of reed sensors (for doors and windows) and flood sensors are still waiting until I decide to wire them.