Atmospheric Pressure Sensor with micro:bit

Get readings from an atmospheric pressure sensor and the micro:bit

Written By: Cherie Tan

Dash icon
Difficulty
Easy
Steps icon
Steps
11

Introduction

A barometric pressure sensor can measure the air pressure and temperature around you. 

In this guide, we will connect a BMP280 barometric pressure sensor to the micro:bit, and program it using MakeCode. 

Complete this guide to start getting pressure and altitude readings with the BMP280 and micro:bit.

Step 1   The Module

  • Voltage is the difference in potential between two points. As it is difficult to talk about voltage without a reference point, we need another point to compare it to. 

  • Before we begin, let's take a closer look at the atmospheric pressure sensor module. It has 6 pins, but we will only be using 4 of them today:

    3.3V  :  'VCC' stands for Voltage Common Collector. We'll connect the VCC pin to 3.3V on the micro:bit

    GND: In electronics, we define a point in a circuit to be a kind of zero volts or 0V reference point, on which to base all other voltage measurements. This point is called  ground or GND.

    Serial Clock (SCL)

    Serial Data (SDA)

Step 2   Connect module to breadboard

Step 3   Connect 3.3V to VCC

Step 4   Connect GND to GND

Step 5   Connect P19 to SCL

Step 6   Connect P20 to SDA

Step 7   Add the BMP280 package

  • Click on Extensions 
  • Type this in the search box: bmp280 
  • Let's get started with coding! Open up the MakeCode editor.
  • Then, click on 'New Project ...' 
  • Click on Advanced 
  • Click on the magnifying glass icon to search
  • Click on BMP280 package and it will be automatically added to the MakeCode editor

Step 8   The MakeCode

let pressure = 0
let temp = 0
basic.forever(function () {
    temp = BMP280.temperature()
    pressure = BMP280.pressure()
    basic.showNumber(temp)
    basic.showNumber(pressure)
    basic.pause(1000)
})
  • Copy and paste this code into the Javascript interface

Step 9   Making sense of the readings

let pressure = 0
let temp = 0
basic.forever(function () {
    temp = BMP280.temperature()
    pressure = BMP280.pressure()
    basic.showNumber(temp)
    basic.showString("degree Celsius")
    basic.showNumber(pressure)
    basic.showString("Pa")
    basic.pause(1000)
})
  • Replace the existing code in the Javascript interface with the following.
  • The temperature reading here will be in Degree Celsius (°C)
  • The pressure reading will be in Pascals (Pa).
  • When you upload this code, there will be two readings on the micro:bit's LED screen, first the temperature in degree Celsius, and the second will be the atmospheric pressure in Pascals.

Step 10   Pressure and Altitude

let t = 0
let prev_p = 0
let p = 0
let damping = 0
damping = 15
prev_p = Math.round(BMP280.pressure() / damping)
basic.forever(function () {
    p = Math.round(BMP280.pressure() / damping)
    t = BMP280.temperature()
    if (p == prev_p) {
        basic.showArrow(ArrowNames.East)
    } else {
        if (p < prev_p) {
            basic.showArrow(ArrowNames.North)
        } else {
            basic.showArrow(ArrowNames.South)
        }
    }
    prev_p = p
    basic.pause(500)
})
  • We've talked about air pressure and temperature. Now let's look at the relationship between air pressure and height or altitude.
  • Air pressure decreases with increasing altitude or height. To see this for yourself, first, paste this code into the Javascript interface.
  • Air pressure is also how drones detect their height and stay stable in the air! 
  • See how  air pressure changes as you move the Micro:bit up and down. 

    When it is not raised, an arrow pointing east will be shown

    Raise it about a meter high up and the arrow will be pointing north

    Bring it back down and the arrow will be pointing south

Step 11   Upload the code

  • To upload the MakeCode to the micro:bit, first connect the micro:bit to your computer using a microUSB cable
  • Over in MakeCode, click on the Download button on the bottom left-hand corner 
  • Find the hex file in the Downloads folder or wherever you might have moved it to
  • Open up Finder on the MacOS or Explorer on Windows, and drag the hex file into MICROBIT under 'Devices' on the macOS.
  • While the code is uploading, the micro:bit will flash for a few seconds. You should then see the temperature and pressure readings scrolling across the 5x5 LED matrix!
© 2022 Little Bird Electronics Pty Ltd.
Made with ❤️ in SYD. All prices inc GST. ABN 15 634 521 449. We're 🐥 @lbhq on Twitter.