Add another i2C sensor to emonth v2

It is possible to add another i2c temperature sensor to emonth v2 ? (Overview | Adafruit SHT31-D Temperature & Humidity Sensor Breakout | Adafruit Learning System)

I did in the past, with emonth v1.4 using dht22 data pin(a4-d18) and ds18b20 data pin (a5 -d19)

But I can’t find the docs in the wiki like v 1.4 and v.1.5 wich are well explained. The v2 redirects to github, where only can find the board png. And there I can only see thar dht22 data pin is D17 (not D18!!!) so I’m missing the possibility of connecting extra I2c devices?. Is the A4-d18 pin accessible and not documented?

This is my first post even though iv had my setup going for a couple of years. I had a emonth v1.4 or v1.5 (cant remember which) and the humidity gave up on the sensor like they usually do after a while. Not wanting to throw it out and not wanting to replace the DHT sensor I decided to have a go at replacing it with the newer si7021.

I removed the old DHT sensor and fitted it with a header for an si7021 breakout board, cut some of the old tracks and linked some new wires to the right places on the emonth, and finally reflashed with emonth v2 hex.

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Welcome, Gary.

Nice one :+1:

I’d be interested in the details of adding the si7021 breakout board and your code for the emonTH!


I think the code for the SI 7021 is already present in the V2 stock firmware. (Except in places it’s called a SI 7201, which is a Hall effect sensor - big potential for confusion there - @gwil can you fix it? )

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good point! I wonder if the si7021 breakout board is wired the same way as the si7021 component… Hopefully Gary @Trev138 is willing to share!

Hello again. Thanks for the kind replies :slight_smile: Its too late tonight but il gladly bring it down from its pole outside (where its been for over a year now) and take some pics of it. Iv gotta say its not very neat and if I was to do it again id probably do it differently!
To confirm other comments yes I used the standard firmware from the EmonTH v2. I cant remember if I used the official USB to serial UART from the shop or avrdude to upload the hex file in the end?

Iv can only attach one pic… any ideas how from the FAQ how I contact someone?
Vin - Connected to 5V (Terminal 1)
GND - Connected to (Terminal 3)
SCL - Connected to DS18B20 data pin (Pin 28 ATMega328)
SDA - Connected to R1 (Pin 27 ATMega328)
I also had to cut the track between R24 and DS18B20 data pin (pull up resistor) because there are already pull ups on the si7021 breakout board and I was having communication issues.

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Your user level has been bumped up so you should be able to post more now.

Thankyou Paul :smile:

Heres one of the underside where iv used a scalpel to remove the original tracks.

Here is a view from the top showing the cut track between R24 and data pin.

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