====== temperature humidity and pressure meter to mqtt (bme280) ======
i wanted to log temperature and humidity values in my sons room as he caughed a lot during the first winter and we had to buy a humidifier. i therefore ordered a BME280 module off Aliexpress for $2.18 (i know, only the best for my kid ;)). The sensor actually mesures both temperature and humidity at a good accuracy and as a "free" bonus it also measures the airpressure. 

my plan is to connect it to a wemos D1 mini and then publish the values via mqtt so i can log them in Home Assistant, Node Red, thingboard or somewhere else. 

===== OpenMQTTGateway =====
first try was with the [[https://github.com/1technophile/OpenMQTTGateway|OpenMQTTGateway]] as i had the arduino IDE ready to go and the code configured and compiled from trying to set up an [[ble_mqtt_gateway]] which sadly did not work, probably due to a DOA module. however, read that article on setting up the OpenMQTTGateway software for flashing. for the BME280 to work you need to enable the ''ZsensorBME280'' in ''User_config.h'', the rest is identical. 

the [[https://github.com/1technophile/OpenMQTTGateway/wiki/ESP8266-I2C-Modules|hardware wiring]] by default looks like this: 
^ I2C Module ^ NodeMCU / ESP8266 ^
| Vcc  | 3.3V |
|GND | GND |
|SCL |D1|
|SDA|D2|
|ADD |N/C (Not Connected|

at least with this sensor it worked right out of the box and reported all sorts of measurements. i could track them using the serial console or via a mqtt client like so: 
  mosquitto_sub -h 192.168.168.1 -u myuser -P mypass -v -t home/#

i think OpenMQTTGateway is still rough around the edges, it works and all but for example the web interface to configure the device is only available if it can't connect to a wifi and therefore goes into setup mode.. this is not ideal as the mqtt parameters could also be managed in there. 

so lets try also 
===== Tasmota =====
also check out my detailed description for the [[sonoff]] setup. basically download the latest [[https://github.com/arendst/Sonoff-Tasmota/releases|release]] and then copy the lib folder into your arduino ''sketchbook/libraries'' folder. then edit the ''my_user_config.h'' file and make sure the ''#define USE_BMP'' is enabled. also sest the ''#define MODULE'' to ''WEMOS''. as a side-note: this will be called "Generic" in the web-interface but in the source code it's still called WEMOS. 

the [[https://github.com/arendst/Sonoff-Tasmota/wiki/Wemos-D1-Mini-and-BME280-Temperature,-Humidity-and-Pressure-Sensor|hardware setup]] looks like this (note, the scl and sda lines could be changed to match OMG for example or vice versa, however, i have it on a breadbord, so i simply changed the patch wires): 
^ I2C Module ^ NodeMCU / ESP8266 ^
| Vcc  |3.3V |
|GND | GND |
|SCL |D4|
|SDA|D3|
|ADD |N/C (Not Connected|

despite selecting the WEMOS module we still have to log into the web interface once the firmware is flashed and booted and go to ''Configuration --> configure module'' and then set ''D3 GPIO0 Button 1'' to I2C ''SDA(06)'' and ''D4 GPIO2'' to ''I2C SCL (05)''. 

now you get a new reading every 5 minutes via MQTT. if you want to change this interval you can either do this in the ''my_user_config.h'' file or via mqtt or the "console" in the web interface by publishing this mqtt topic and value: 
  tasmota/sonoff/cmd/TelePeriod 30
this will set it to 30 seconds