node-red-contrib-bme280

A node-red custom node wrapper for the nodejs bme280-sensor. by @skylarstein . This library uses the outstanding package i2c-bus that enable the communication with I2C devices in most common Linux SBCs. Raspberry Pi, C.H.I.P., BeagleBone, Orange Pi, or Intel Edison are supported by this package.

The package provide a single custom node Bme280 that can be used directly in your flow.

Installation

Under your node-red (typically $HOME/.node-red) working directory.

npm install node-red-contrib-bme280

Node palette can be used as well to install the node.

After restarting node-red the "Bme280" node should be available in "input" category.

Prerequisites

Wire your sensor the I2C/TWI of the SBCs. Only four wires are needed. two for power (VCC 3.3V & GND) and two for actual I2C transmission (SLC & SDA).

I2C interface need to be enabled in in your linux distribution.

Caveat: Check your permissions to the /dev/i2c-xx devices. The user running node-red need access to writing and reading. Refer to i2c-bus to find how to grant access to your user to the /dev/i2c-xx device files

Usage

Configuration & deployment

After installation place your Bme280 node in any of your flow and configure the following parameters:

1. Name: Select the name of your sensor for easy identification.
2. Bus ID: Select the I2C bus to which the sensor is connected. Depending on your wiring and SBC can be different.
3. I2C address: I2C address (7-bit) hexdecimal address(0x##). BMP/BME280 sensor have fixed 0x77 or 0x76. You can check your sensor id by using i2c-tools typing i2cdetect -y <busnum>
4. Topic: Topic field set on the output message. If this field is empty, topic will not be included in the output msg. By configuring the node this way input msg topic will be reused.
5. Extra: Check box to indicate the node to compute extra information each time a read is requested.
6. Sea Preasure: If extra information provided this parameter is used for correction. The value is in hPa.

After configuration and deployment the node will init the sensor and will identify if BME280 or BMP280 variant is detected.

Reading Sensor Data

As in other node-red nodes the actual measurement of sensor data require that an input msg arrive to the node. The input called Trigger will start the reading of sensor data will send the data in the node's output. The input msg is reused so any property on the input msg (with the exception of payload and topic if set) will be redirected without modification to the output.

The output will have the following format:

msg = {
  _msgid: <node-red msg_id>,
  topic: <defined topic>,
  payload: {
    model: "BME280"  or  "BMP280",
    temperature_C: <float in celsius>,
    humidity: <float in %>, // Only present if model == "BME280"
    pressure_hPa: <float in hPa>
  }
}

// the node node is configured to send extra information payload will contain also

payload: {
     ....
     heatIndex: <float in celsius>, // Only present if model == "BME280"
     dewPoint_C= <float in celsius>, // Only present if model == "BME280"
     altitude_M= <float in Meters>,
     temperature_F=<float in fahrenheit>
     pressure_Hg=<float in mm of mercury>
}

Note: BMP280 version WILL NOT report humidity information the sensor do not provide this information. humidity, heatIndex & dewPoint_C will not be present in the payload.

Notes

This node has been tested on Raspberry Pi 3, Raspberry Pi Zero & Orange Pi Zero. Running recent versions of node-red.

BPM280 & BME280 has been tested using different breakout from cheap providers. Original Adafruit's sensor is not required.

Change log

• 1.1.0 Stable version

  • Added max init retries to avoid continous use of I2C bus
  • Added message bypass in case of error.
  • Added parameter for sea level presasure to calculate properly altitude.

• 1.0.0 Stable version

  • Sensor init is done also in input trigger for better stability.

• 0.0.5

  • Fix #2 for nodejs >=13 compatibility

• 0.0.4

  • Improve node status messages.

• 0.0.3

  • Custom Icon
  • Topic configurable to help MQTT integration
  • Input msg will be reused to enable better HTTP node integration.
  • Documentation improvements
  • Added some examples.

• 0.0.2 Solved npm repository name.

• 0.0.1 First version