# Atmospheric Pressure Sensor with micro:bit

Difficulty
Easy
Steps
11

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.

Parts Used in This Guide

## Step 1  The Module

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.
• Note: 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.
• Serial Clock (SCL)
• Serial Data (SDA)

## Step 7  Add the BMP280 package

Let's get started with coding!

1. Open up the MakeCode editor
2. Then, click on 'New Project ...'
4. Click on Extensions
5. Type this in the search box: bmp280
6. Click on the magnifying glass icon to search
7. Click on BMP280 package and it will be automatically added to the MakeCode editor!

## Step 8  The MakeCode!

• From the variables tab, click on 'Make a variable ...'
• Name the variable, 'temp'
• Now drag and drop a 'get temperature' block from BMP280 tab into the editor
• Assign it to the variable, 'temp'.
• Create another variable, but this time name it 'pressure'.
• Again, click on the BMP280 tab but this time, drag and drop a 'get pressure' block into the editor.
• Assign it to the variable, 'pressure'.
• To show the temperature and pressure readings, we use 'show number' blocks.
• Then we assign their values to 'temp' and 'pressure'.
• Finally, add a 'pause (ms) 1000' block at the end of the forever loop.
By adding this, the micro:bit will display a value and pressure reading every 1 second. You will see the readings scroll across the micro:bit's 5x5 LED matrix!

## Step 9  Making sense of the readings!

• The temperature reading here will be in Degree Celsius (°C)
• The pressure reading will be in Pascals (Pa).
• So add a 'show string' block from 'Basic' tab, and change its value to 'degree Celsius'.
• Place this under 'show number temp' block.
• Duplicate the 'show string' block by right-clicking it and selecting 'Duplicate'.
• Now change its value to 'Pa', move this block under 'show number pressure'
• 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!

• 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, grab this MakeCode by clicking the Download button below.
• 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

1. Connect the micro:bit to your computer using a microUSB cable
2. Over in MakeCode, click on the Download button on the bottom left-hand corner
3. Find the hex file in the Downloads folder or wherever you might have moved it to
4. Open up Finder on the MacOS or Explorer on Windows, and drag the hex file into MICROBIT under 'Devices' on the macOS.
5. While the code is uploading, the micro:bit will flash for a few seconds

You should now see the temperature and pressure readings scrolling across the 5x5 LED matrix!