BMP180 Digital pressure SENSOR

In this example we are going to connect from Raspberry Pi to BMP180 digital pressure sensor, we will be using brake-out board called GY-68.

(And at bottom there I tell of how to get it to work also on H3 based Orange Pi)

This sensor can act as Barometer and it also measures temperature.

Main parameters from the sensors Data sheet:

• Pressure range: 300 ... 1100hPa (+9000m ... -500m relating to sea level).
• Supply voltage: 1.8 ... 3.6V (VDD)      1.62V ... 3.6V (VDDIO).
• Power usage: 5μA at 1 sample / sec. in standard mode.
• Modes:  Ultra low power, Standard, High resolution, Ultra high resolution.
• Pressure resolution:  1 Pa.
• Temperature resolution:  0.1° C.
• Interfaces:  I2C.

This sensor is really small even the full brake-outboard is only size of a fingernail. The board does not come with the header pins soldered on, but with mine the header pins came with it at least so I just had to solder them on.

Pieces we use in this guide:

• Raspberry Pi 2, 3, 4 or 5. 
• Cobbler and Cobbler cable.
• Breadbboard.
• BMP180 sensor on GY68 or other similar brake-out board.
• I2C Plugin to use libi2c in Xojo. The plugin you can download here. Or if you are interested in its source code then you can go here.
• I2C Tools need to be installed on the Raspberry Pi and I2C needs to be enabled in the Raspberry Pi settings.

I2C Tools

To install the I2CTools you use the following command:

sudo apt-get install i2c-tools

You need to enable the i2c bus in the Raspberry PI settings, which you can do in the Raspberry Pi user interface.

Wiring up the board:

First we solder the header pins into the brake-out board as shown bellow. It was possible on mine to either solder the pins on front or back.

Once the board has been soldered with header pins or wires then we are ready to wire up the sensor which we do as follows:

Sanity tests in console:

After you have connected everything and made sure that wiringPI, i2ctools are installed that I2C is enabled in the Raspberry PI settings, then we are ready to do sanity tests in console, or you can run the I2C example project that comes with the I2C Plugin.

If doing it in console then you would issue command like this:

sudo i2cdetect -y 1

This should show our device at 0x77. Or if you use the example project that comes with the I2C plugin then you click Get adapters and then select the adapter and then click Scan the selected adapter this should get you 119, which converted to Hex is 0x77, same as the i2cdetect returns.

The example project that comes with the I2C Plugin, which can help you scan for the device address.

If you can see your sensor on address 0x77 (or 119 dec) then you are ready to start coding.

The Xojo code:

Coding against this sensor is somewhat complicated but I have made it really simple as I created a Xojo class called BMP180 (see download
link at bottom) that does all the hard work. Using the class is as very easy:

Getting the chip id to verify everything is all right:

Sub Pressed() Handles Pressed
  #if TargetARM and TargetLinux
    try
      // We want adapter 1 and device 0x77
      var bmp as new BMP180(1, &h77)
      
      MessageBox("0x" + Hex(bmp.GetChipID()))
      
    catch ex as I2CException
      MessageBox("Error: " + ex.Message)
    end try
    
  #endif
End Sub

Read temperature:

Sub Pressed() Handles Pressed
  #if TargetARM and TargetLinux
    try
      // We want adapter 1 and device 0x77
      var bmp as new BMP180(1, &h77)
      
      MessageBox(Format(bmp.ReadTemperature(),"#.0") + "° C")
      
    catch ex as I2CException
      MessageBox("Error: " + ex.Message)
    end try
    
  #endif
End Sub

Read pressure:

Sub Pressed() Handles Pressed
  #if TargetARM and TargetLinux
    try
      // We want adapter 1 and device 0x77
      var bmp as new BMP180(1, &h77)
      
      MessageBox(Format(bmp.ReadPressure(BMP180.Mode.STANDARD),"#.0"))
      
    catch ex as I2CException
      MessageBox("Error: " + ex.Message)
    end try
    
  #endif
End Sub

Read pressure at sea level:

Sub Pressed() Handles Pressed
  var heightOverSeaLevel as Single = Val(tbHeightOverSeaLevel.Text)
  
  #if TargetARM and TargetLinux
    try
      // We want adapter 1 and device 0x77
      var bmp as new BMP180(1, &h77)
      
      MessageBox(Format(bmp.ReadPressureAtSeaLevel(BMP180.Mode.ULTRALOWPOWER,heightOverSeaLevel),"#.0"))
      
    catch ex as I2CException
      MessageBox("Error: " + ex.Message)
    end try
    
  #endif
End Sub

To get your current height above sea level then you can for example use this page here: WhatsMyElevation

When testing the example then I found I was 118 meter above sea level which I used to calculate pressure at sea level.

I got this also to work on H3 based Orange Pi running Armbian.

To get things to work on H3 based Orange Pi I had to:

• Enable i2c in armbian-config by going in sudo armbian-config.
• Install libi2c (am not 100% sure this step was needed)  sudo apt-get install libi2c-dev
• I found the sensor on i2c bus zero so I had to update the Xojo code to talk to i2c bus zero instead of one.
• Run the application as admin with sudo. (Since Armbian has more strict settings by default on running i2c and gpio).