[Solved] 2nd BMP180 on Pi

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Hey,
I’m searching for a solution to get a second BMP180 connected to my Pi, because it has a fix non changeable address.
The first one is working with the Johnny-Five plugin on a Rasb Pi 3.

So what do I need to do, to get the second one running as well?
Is there a way to change the address? Or a gateway (routing messages between busses?
I’m not quite sure if it’s possible to use multiplexer with the plugin? Or an Expander(looks like that the supported boards has only A/D pins) ?

Would be great if s.o. has an idea.
Thanks

@free118 I don’t think it is possible. The BMP180 has a single, unchangeable address, so if you put two on the same I2C bus they will conflict with each other. Moreover, the BMP180 does not have a reset pin like its predecessor BMP085 (discontinued) had. Such a reset pin could be used to mux between the two sensors. Ways forward:

• Combine one BMP180 with a different sensor, e.g. MPL3115A2 or BMP280 which use different addresses. The latter, BMP280 even allows for wiring up the addresses you want. All of these sensors can be used with pimatic-johnny-five
• Establish a second i2c bus on raspi. There are software libraries to do that, but I am not sure about the implication this may have. Most likely you’d need to write your driver to switch between busses
• Use pimatic-johnny-five and connect the second pressure sensor via an Arduino connected to the Raspi via USB.
• build an i2c multiplexer and write your own software driver

In summary, I think the first option is the best to give it a try.

See also
https://martin-jones.com/2013/08/20/how-to-get-the-second-raspberry-pi-i2c-bus-to-work/
http://electronics.stackexchange.com/questions/5096/how-to-resolve-i2c-address-clashes

maybe not the answer yo uare looking for but a possible workaround would be either with an arduino or with an esp8266. you can use espeasy and the bmp sensor

@mwittig @leader21,
thanks guys for your quick answer. I will go with the BMP280, because i think adding an arduino is a little bit oversize in my usecase.
Maybe i will do that when i need an analog in, which i have tried and worked, but didn’t need it right know.
Thanks again.

Hello,
I’ve received the BMP280 and connected to the Pi IO.
So the bus looks good. I see all devices on the Bus.
I can create the second the device w/o any issues, but the measurement value is the same as the first one. The sensors are in different areas one is in a pressure box and one measuring the “normal” pressure. When is increase the pressure in “Druckdose” than Umgebungsdruck increases as well.
I’ve a attached a part of my config.

{
      "id": "Druck",
      "name": "Druckdose",
      "class": "JohnnyFiveTemperaturePressure",
      "boardId": "1",
      "controller": "BMP180",
      "interval": 1800,
      "units": "metric",
      "xAttributeOptions": [],
      "address": "0x77"
    },
    {
      "id": "Umgebungsdruck",
      "name": "Umgebungsdruck",
      "class": "JohnnyFiveTemperaturePressure",
      "boardId": "1",
      "interval": 1800,
      "units": "metric",
      "xAttributeOptions": [],
      "address": "0x76",
      "controller": "BMP180"
    }

Looks like that the address attribute is ignored somewhere?!
Thanks
Free

@free118 I have tested your with similar settings and confirm this si a bug. I am working on it.

https://github.com/mwittig/pimatic-johnny-five/issues/47

@free118 Should be fix now -> pimatic-johnny-five@0.9.6

Please keep me posted

@mwittig Works perfectly. Thank for this fast fix.

@free118 Great. Thanks for reporting