With this project we will take some common off the shelf components and build an aviation style altimeter. This will feature a temperature compensated barometer and a 4 line LCD screen. We will Display the altitude, current pressure setting, and temperature. The pressure setting will be adjustable with two monetary switches up and down. If you are not familiar with aviation you can get the setting by looking up the METAR from a local airport. The easiest place to look up the METAR is through, once you type in your ZIP Code under current settings there will be a METAR section look for the piece that looks like A3005 which says the current setting is 30.05 inHg (how to read METAR).

mounted LCD with readout

Wiring Diagrams

Connecting the LCD to the Arduino


Arduino Mega Pin

1 (VSS)

GND Arduino pin

2 (VDD)

+ 5v Arduino pin

3 (contrast)

Resistor to GND Arduino pin

4 RS

Arduino pin 12

5 R/W

Arduino pin 11

6 Enable

Arduino pin 10

7 No connection


8 No connection


9 No connection


10 No connection


11 Data 4

Arduino pin 5

12 Data 5

Arduino pin 4

13 Data 6

Arduino pin 3

14 Data 7

Arduino pin 2

15 Backlight +

Resistor to Arduino pin 13

16 Backlight GND

GND Arduino pin

Connection Barometric Sensor to Arduino


Arduino Pin

1 (VCC)

3.3v Arduino pin

2 (GND)

GND Arduino pin

3 (EOC)


4 (XCLR)


5 (SCL)

21 (SCL) [MEGA 2560] *

6 (SDA)

20 (SDA) [MEGA 2560] **

* Pin A5 on the UNO
** Pin A4 on the UNO

Wiring of the Buttons

Up Button

Arduino Pin


Analog pin 1


+ 5v Arduino pin

Down Button

Arduino Pin


Analog in 2


+ 5v Arduino pin

Source Code

Parts List

General parts, choose ones that will fit your goals


  • Wire cutters - small
  • X-ACTO knife. or utility knife
  • soldering iron

Additional Resources

If you have questions or would like to discuss other aspects of this project please do so on our forums.
Altimeter Forum Discussion