1. Logic Gates Practical
Objective: to develop an understanding of logic circuits and truth tables.

2. Binary
Humans count using the decimal (aka denary) number system.
Computers count using the binary number system as it can represent the two states of an electronic circuit.
On = 1
Off = 0

3. Logic Gates
Logic gates are the fundamental building blocks of digital circuits.
There are three main logic gates:
NOT
AND OR
Each logic gate is represented by a different symbol.

4. Activity 1
In pairs, look at the program below and write out what you think might happen when it runs on a micro:bit:
What would you expect the micro:bit to do?

5. Activity 2
Working in pairs, download and flash the starter program onto one of your micro:bits and create the circuit shown in the diagram below (make sure the micro:bit is connected to a USB port):

6. Activity 3 In pairs answer the following questions: Question Answer
Give an example of how selection is used in the starter program.
What happens to the LED when switch is in the OFF position?
What happens to the LED when switch is in the ON position?

7. Activity 4a
We use truth tables to show all the different possible states of a logic circuit.
This is a partially complete truth table for a NOT gate logic circuit. It shows all the possible inputs.
Use your logic circuit to help you fill in the outputs (LED ON = 1, LED OFF = 0).
Input
Output 1

8. Activity 4b
Working in your pair, divide the following tasks between you and complete them:
Task 1: Adapt the starter program to simulate an AND gate. Ensure you update the symbol that displays on the micro:bit.
The AND gate outputs a 1 if both inputs are 1.
Symbol:
Task 2: Adapt the starter program to simulate an OR gate. Ensure you update the symbol that displays on the micro:bit.
The OR gate outputs a 1 if either or both inputs are 1.
Symbol:
Hint: These gates have two inputs instead of one, you will need to use pin 1 for the second input. In the NOT gate program we checked only pin 0, in this program you will need to check both pin 0 and pin 1.

9. Activity 4c
Flash your micro:bits with your new programs and create the circuit shown below with the micro:bit that has the AND gate program:

10. Activity 4d
Use your new circuit to help you complete this truth table:
AND
Input 1
Input 2
Output 1

11. Activity 4e
Change the micro:bit in your circuit to the one containing the OR gate program. Use the circuit to help you complete this truth table: OR
Input 1
Input 2
Output 1

12. Challenge
Create a new program that lets the user select which logic gate they want to use by pressing the buttons on the micro:bit:
Button A = NOT
Button B = AND
Buttons A + B = OR
Hint: The code below shows you how to check whether a button has been pressed:

13. Challenge
Create a new program that lets the user select which logic gate they want to use by pressing the buttons on the micro:bit:
Button A = NOT
Button B = AND
Buttons A + B = OR
Hint: The code below shows you how to check whether a button has been pressed: