Time’s Up! Build a PicoBricks Timer

Overview

In this project we are going to create our own countdown timer using PicoBricks.

Measuring time in electronic projects is really important. Think about a washing machine. It needs to know how long to spin the drum in each direction and how long the water needs to flow to dissolve the detergent.

Our timer will work a bit like that. When PicoBricks starts, it shows a welcome message and instructions for using the timer. As you turn the , it sets a value. Each press of the locks that value in and moves you on to the next one: first the hours, then the minutes, then the seconds.

Once the time is set, the countdown begins and the remaining time is shown on the . When the timer reaches zero, the sounds and the LEDs light up until you press the button to stop them.

🎯

What you'll learn

How to control and count down time within a project
How to read a potentiometer to set a value
How to use functions to keep your code tidy and reusable
How to show numbers and messages on an OLED screen
How to use a buzzer and LEDs to make an alarm

What you'll need

PicoBricks Kit
PicoBricks Brick IDE
MicroUSB to USB cable
Laptop or tablet for coding

Key words

Potentiometer

A potentiometer is a knob or dial that controls how much electricity flows through a circuit. Think of it like a tap for water: turn it one way and more comes out, turn it the other way and less comes out.

Real-world example: A volume dial on a speaker is a potentiometer, turn it up for louder sound and down for quieter.

Button

A button is a switch you press to tell your project to do something. The code can check whether it's being pressed or not.

Real-world example: Pressing a doorbell is just like pressing a button, one press sends a signal that makes something happen.

OLED screen

An OLED screen is a small display that shows words, numbers and pictures from your code. On some kits it's labelled the "LED display", but it's the same little screen.

Real-world example: Like the small screen on a fitness watch showing your steps, an OLED screen can show a score or a countdown.

Buzzer

A buzzer is a tiny speaker that makes beeps and tones when you send it electricity. By telling it different numbers, you can make it play notes and tunes.

Real-world example: The beep a microwave makes when your food is ready comes from a buzzer.

Variable

A variable is something that can change. Think of it like a labelled box: you pop something inside, and the label tells you what it is. You can swap what's inside whenever you like.

Real-world example: A variable called score might start at 0, then change to 1, 2 and 3 as you collect points in a game.

Function

A function is a chunk of code you give a name to, so you can use it again and again without building it from scratch each time. Think of it like a favourite recipe, you write down the steps once, then follow it whenever you need it.

Real-world example: Like writing out a pancake recipe once. Whenever you fancy pancakes, you just follow the recipe again rather than working it all out from scratch.

While loop

A while loop keeps repeating its instructions for as long as something stays true. The moment that thing stops being true, the loop stops.

Real-world example: "While it's still raining, keep the umbrella up." As soon as the rain stops, you put the umbrella down, and the loop ends.

Forever loop

A forever loop repeats its instructions again and again without ever stopping (until you switch off or reset). It's perfect for anything you want to keep happening over and over.

Real-world example: Like a clock's second hand that keeps ticking round and round, a forever loop keeps running the same steps over and over.

If statement

An if statement checks whether something is true, and only runs its instructions when it is. It's how code makes decisions.

Real-world example: "If it's cold, put on a coat." If it's warm, you skip the coat, the action only happens when the check is true.

Set up your PicoBricks

Open your favourite web browser. We recommend Google Chrome or Microsoft Edge.
Type ide.picobricks.com into the address bar to open the PicoBricks coding editor.
Connect the PicoBricks board to your computer with the USB cable.
Select the Connection button at the top of your code editor to pair the Raspberry Pi Pico with the code editor.

The PicoBricks Brick IDE coding environment

Build the starter function

First, we will create a that shows a welcome message on the screen. This tells the person using the timer what to do before they start.

Select Functions. Select a to do something block and drop it within the code area.
Change do something to StarterFunction.
Select Loops. Select a block and snap it inside the to StarterFunction block.
Select Logic. Select an = block and snap it onto the while block.
Select Bricks. Select a Read Button block and snap it onto the while block before the = sign.
Select Math. Select a 0 block and snap it onto the while block after the = sign.
Select Display. Select a Write Text to Screen block and snap it inside the while Read Button = 0 block.
Change the X value to 10 and change PicoBricks to << My Timer >>.
Select Display. Select another Write Text to Screen block and snap it under the first one.
Change the Y value to 15 and change PicoBricks to Press the Button.
Select Display. Select another Write Text to Screen block and snap it under that.
Change PicoBricks to To START!
Select Display. Select another Write Text to Screen block and snap it underneath.
Change the X value to 15, the Y value to 45, and change PicoBricks to Use the POT.
Select Display. Select another Write Text to Screen block and snap it underneath.
Change the X value to 10, the Y value to 55, and change PicoBricks to to Set the Timer.
Select Display. Select a Show Screen Buffer block and snap it underneath.

💡

POT is short for potentiometer. That is the little dial we will turn to set the timer.

The completed StarterFunction blocks

Build the hour function

Next, we will create the hour function. This lets us use the potentiometer to choose how many hours we want on the timer.

Select Functions. Select a to do something block and drop it within the code area.
Change do something to hour.
Select Loops. Select a while block and snap it inside the to hour block.
Select Logic. Select an = block and snap it onto the while block.
Select Bricks. Select a Read Button block and snap it onto the while block before the = sign.
Select Math. Select a 0 block and snap it onto the while block after the = sign.
Select Display. Select a Clear Screen Buffer block and snap it inside the while Read Button = 0 block.
Select Display. Select a Write Text to Screen block and snap it under the Clear Screen Buffer block.
Change the X value to 35 and the Y value to 30.
Select Variables. Select Create Variable and type hourValue.
Select a hourValue block and snap it onto the Write Text to Screen block where it says PicoBricks.
Select Display. Select a Show Screen Buffer block and snap it underneath.
Select Variables. Select a set hourValue to block and snap it under the Show Screen Buffer block.
Select Math. Select a round block and snap it onto the set hourValue to block.
Select Math. Select a 1 + 1 block and snap it onto the round block where it says 3.1.
Change the + to x.
Select Bricks. Select a Read Potentiometer block and snap it into the first 1 of the maths block.
Select Math. Select a 1 + 1 block and snap it into the second 1 of the maths block.
Change the first 1 to 24, the + sign to ÷, and the remaining 1 to 65535.
Select Variables. Select Create Variable and type due.
Select a set due to block and snap it below the set hourValue to round Read Potentiometer x 24 ÷ 65535 block.
Select Math. Select a 0 block and snap it onto the set due to block.
Change the 0 to 1.

🧠

This part turns the dial reading into a number of hours. The due variable helps the code know which part of the timer setup should happen next.

The completed hour function blocks

Build the minutes function

The minutes function works almost the same way as the hour function, but this time it sets the minutes.

Select Functions. Select a to do something block and drop it in the code area.
Change do something to minutes.
Select Loops. Select a while block and snap it inside the to minutes block.
Select Logic. Select an = block and snap it onto the while block.
Select Bricks. Select a Read Button block and snap it onto the while block before the = sign.
Select Math. Select a 0 block and snap it onto the while block after the = sign.
Select Display. Select a Clear Screen Buffer block and snap it within the while Read Button = 0 block.
Select Display. Select a Write Text to Screen block and snap it under the Clear Screen Buffer block.
Change the X value to 55 and the Y value to 30.
Select Variables. Select Create Variable and type minuteValue.
Select a minuteValue block and snap it onto the Write Text to Screen block where it says PicoBricks.
Select Display. Select a Show Screen Buffer block and snap it underneath.
Select Variables. Select a set minuteValue to block and snap it under the Show Screen Buffer block.
Select Math. Select a round block and attach it within the set minuteValue to block.
Select Math. Select a 1 + 1 block and attach it within the 3.1 of the round block.
Change the + sign to x.
Select Bricks. Select a Read Potentiometer block and snap it within the first 1 of the maths block.
Select Math. Select a 1 + 1 block and snap it within the second 1 of the maths block.
Change the first 1 to 60, the + to ÷, and the remaining 1 to 65535.
Select Variables. Select a set minuteValue to block and snap it underneath.
Change minuteValue to due.
Select Math. Select a 0 block and snap it onto the set due to block.
Change 0 to 2.

The completed minutes function blocks

Build the seconds function

Now we will create the seconds function. This sets the seconds before the countdown begins.

Select Functions. Select a to do something block and drop it in the code area.
Change do something to seconds.
Select Loops. Select a while block and snap it within the to seconds block.
Select Logic. Select an = block and snap it onto the while block.
Select Bricks. Select a Read Button block and snap it onto the while block before the =.
Select Math. Select a 0 block and snap it onto the while block after the =.
Select Display. Select a Clear Screen Buffer block and snap it within the while Read Button = 0 block.
Select Display. Select a Write Text to Screen block and snap it under the Clear Screen Buffer block.
Change the X value to 75 and the Y value to 30.
Select Variables. Select Create Variable and type secondsValue.
Select a secondsValue block and snap it onto the Write Text to Screen block where it says PicoBricks.
Select Display. Select a Show Screen Buffer block and snap it underneath.
Select Variables. Select a set secondsValue to block and snap it under the Show Screen Buffer block.
Select Math. Select a round block and snap it onto the set secondsValue to block.
Select Math. Select a 1 + 1 block and snap it onto the round block where it says 3.1.
Select Bricks. Select a Read Potentiometer block and snap it into the first 1.
Change the + sign to x.
Select Math. Select a 1 + 1 block and snap it into the second 1.
Change the first 1 to 60, the + to ÷, and the remaining 1 to 65535.
Select Variables. Select a set secondsValue to block and snap it underneath.
Change secondsValue to due.
Select Math. Select a 0 block and snap it to the set due to block.
Change the 0 to 3.

The completed seconds function blocks

Build the clock function

The clock function puts the hours, minutes and seconds together on the OLED screen.

Select Functions. Select a to do something block and drop it in the code area.
Change do something to clock.
Select Display. Select a Clear Screen Buffer block and snap it within the to clock block.
Select Display. Select a Write Text to Screen block and snap it under the Clear Screen Buffer block.
Change the X value to 35 and the Y value to 30.
Select Variables. Select a hourValue block and snap it onto the Write Text to Screen block where it says PicoBricks.
Select Display. Select a Write Text to Screen block and snap it underneath.
Change the X value to 50, the Y value to 30, and change PicoBricks to :.
Select Display. Select another Write Text to Screen block and snap it underneath.
Change the X value to 55 and the Y value to 30.
Select Variables. Select a minuteValue block and snap it onto the block where it says PicoBricks.
Select Display. Select another Write Text to Screen block and snap it underneath.
Change the X value to 70, the Y value to 30, and change PicoBricks to :.
Select Display. Select another Write Text to Screen block and snap it underneath.
Change the X value to 75 and the Y value to 30.
Select Variables. Select a secondsValue block and snap it onto the block where it says PicoBricks.
Select Display. Select a Show Screen Buffer block and snap it underneath.

The completed clock function blocks

Build the control function

The control function checks whether the countdown has finished. When the timer reaches zero, it switches on the alarm.

Select Functions. Select a to do something block and drop it in the code area.
Change do something to control.
Select Logic. Select an block and snap it within the to control block.
Select Logic. Select an and block and snap it onto the if block.
Select Logic. Select an = block and snap it within the if block before the and.
Select Variables. Select a hourValue block and snap it onto the if block before the = sign.
Change the = sign to a < sign.
Select Math. Select a 0 block and snap it onto the if block before the and.
Change the and to or.
Select Logic. Select an and block and snap it onto the if block after the or.
Select Logic. Select an = block and snap it onto the if block before the and.
Select Variables. Select a minuteValue block and snap it onto the if block within the blank space after the or.
Change the = to <.
Select Math. Select a 0 block and snap it onto the if block after the < symbol.
Change the and to or.
Select Logic. Select an = block and snap it onto the if block after the or.
Select Variables. Select a secondsValue block and snap it onto the if block after the or.
Change the = to a < symbol.
Select Math. Select a 0 block and snap it within the remaining blank space of the if block.
Select Variables. Select a set secondsValue to block and snap it within the if hourValue < 0 or minuteValue < 0 or secondsValue < 0 do block.
Change secondsValue to hourValue.
Select Math. Select a 0 block and snap it onto the set hourValue to block.
Select Variables. Select a set secondsValue to block and snap it underneath.
Change secondsValue to minuteValue.
Select Math. Select a 0 block and snap it onto the set minuteValue to block.
Select Variables. Select a set secondsValue to block and snap it underneath.
Select Math. Select a 0 block and snap it onto the set secondsValue to block.
Select Variables. Select a set secondsValue to block and snap it underneath.
Change secondsValue to due.
Select Math. Select a 0 block and snap it onto the set due to block.
Change 0 to 4.
Select Functions. Select a clock block and snap it underneath.
Select Bricks. Select a Set Led block and snap it underneath.
Select Bricks. Select a Play Buzzer Freq block and snap it underneath.
Change 300 to 800.
Select RGB LED. Select a Set RGB Led Colour block and snap it underneath.

🚨

This is the alarm part of the timer. When the countdown finishes, the buzzer sounds and the lights turn on.

The completed control function blocks

Build the timer function

Now it is time to build the timer function. This is the part that counts down the time.

Select Functions. Select a to do something block and drop it in the code area.
Change do something to timerFunction.
Select Functions. Select a control block and snap it within the timerFunction block.
Select Loops. Select a while block and snap it underneath the control block.
Select Logic. Select an and block and snap it onto the while block.
Select Logic. Select an = block and snap it onto the while block before the and.
Select Variables. Select a hourValue block and snap it onto the while block before the = sign.
Change the = sign to a ≥ sign.
Select Math. Select a 0 block and snap it after the ≥ sign.
Select Logic. Select an and block and snap it onto the while block after the and.
Select Logic. Select an = block and snap it onto the while block between the two and blocks.
Select Variables. Select a minuteValue block and snap it onto the while block before the = sign.
Change the = sign to a ≥ sign.
Select Math. Select a 0 block and snap it after the ≥ sign.
Select Logic. Select an = block and snap it onto the while block after the and.
Select Variables. Select a secondsValue block and snap it onto the while block before the = sign.
Change the = sign to a ≥ sign.
Select Math. Select a 0 block and snap it after the ≥ sign.
Select Loops. Select a repeat block and snap it within the while hourValue ≥ 0 and minuteValue ≥ 0 and secondsValue ≥ 0 block.
Select Variables. Select a secondsValue block and snap it onto the repeat block.
Select Functions. Select a clock block and snap it within the repeat secondsValue times block.
Select Variables. Select a change secondsValue by block and snap it under the clock block.
Change the 1 to -1.
Select Loops. Select a wait block and snap it underneath.
Select Basic. Select a Serial Print block and snap it underneath.
Select Variables. Select a secondsValue block and snap it onto the Serial Print block where it says PicoBricks.
Select Logic. Select an if block and snap it under the repeat secondsValue times block.
Select Logic. Select an = block and snap it onto the if block.
Select Math. Select a 0 block and snap it onto the if block before the = sign.
Select Variables. Select a change secondsValue by block and snap it within the if secondsValue = 0 block.
Change secondsValue to minuteValue and 1 to -1.
Select Basic. Select a Serial Print block and snap it underneath.
Select Variables. Select a minuteValue block and snap it onto the Serial Print block where it says PicoBricks.
Select Functions. Select a clock block and snap it underneath.
Select Variables. Select a set secondsValue to block and snap it underneath.
Change 1 to 60.
Select Logic. Select an if block and snap it underneath.
Select Logic. Select an = block and snap it onto the if block.
Select Variables. Select a minuteValue block and snap it onto the if block before the = sign.
Select Math. Select a 0 block and snap it onto the if block after the = sign.
Select Functions. Select a clock block and snap it within the if minuteValue = 0 block.
Select Variables. Select a set secondsValue to block and snap it under the clock block.
Change secondsValue to minuteValue.
Select Math. Select a 0 block and snap it onto the set minuteValue to block.
Change the 0 to 60.
Select Variables. Select a change secondsValue by block and snap it underneath.
Change secondsValue to hourValue and 1 to -1.
Select Basic. Select a Serial Print block and snap it underneath.
Select Variables. Select a hourValue block and snap it onto the Serial Print block where it says PicoBricks.

The completed timer function blocks

Build the starter code

We have now created all the functions. The last job is to create the main code that runs when PicoBricks starts.

Select Basic. Select a PicoBricks block and drop it in the code area.
Select Functions. Select a StarterFunction block and snap it to the PicoBricks block.
Select Display. Select a Clear Screen Buffer block and snap it underneath.
Select Variables. Select a set secondsValue to block and snap it underneath.
Change secondsValue to hourValue.
Select Math. Select a 0 block and snap it onto the set hourValue to block.
Select Variables. Select a set secondsValue to block and snap it underneath.
Change secondsValue to minuteValue.
Select Math. Select a 0 block and snap it onto the set minuteValue to block.
Select Variables. Select a set secondsValue to block and snap it underneath.
Select Math. Select a 0 block and snap it onto the set secondsValue to block.
Select Variables. Select a set secondsValue to block and snap it underneath.
Change secondsValue to due.
Select Math. Select a 0 block and snap it onto the set due to block.
Select Loops. Select a block and snap it underneath.
Select Logic. Select an if block and snap it within the forever block.
Select Logic. Select an = block and snap it onto the if block.
Select Variables. Select a due block and snap it onto the if block before the = sign.
Select Math. Select a 0 block and snap it onto the if block after the = sign.
Select Functions. Select a hour block and snap it into the if due = 0 do block.
Select the + on the if block two times to create an else if block.
Select Logic. Select an = block and snap it onto the else if block.
Select Variables. Select a due block and snap it onto the else if block before the = sign.
Select Math. Select a 0 block and snap it onto the else if block after the = sign.
Change the 0 to 1.
Select Functions. Select a minutes block and snap it within the else if due = 1 do block.
Select the + sign at the bottom of the if block to create another else if block.
Select Logic. Select an = block and snap it onto the else if block.
Select Variables. Select a due block and snap it onto the else if block before the = sign.
Select Math. Select a 0 block and snap it onto the else if block after the = sign.
Change the 0 to 2.
Select Functions. Select a seconds block and snap it within the else if due = 2 do block.
Select the + sign at the bottom of the if block to create another else if block.
Select Logic. Select an = block and snap it onto the else if block.
Select Variables. Select a due block and snap it onto the else if block before the = sign.
Select Math. Select a 0 block and snap it onto the else if block after the = sign.
Change the 0 to 3.
Select Functions. Select a clock block and snap it within the else if due = 3 do block.
Select Functions. Select a timerFunction block and snap it under the clock block.
Select Functions. Select a control block and snap it within the else block.
Select Logic. Select an if block and snap it under the control block.
Select Logic. Select an = block and snap it onto the if block.
Select Bricks. Select a Read Button block and snap it onto the if block before the = sign.
Select Math. Select a 0 block and snap it onto the if block after the = sign.
Change 0 to 1.
Select Bricks. Select a Set Led block and snap it within the if Read Button = 1 do block.
Change on to off.
Select Bricks. Select a Stop Buzzer Interval block and snap it underneath.
Select RGB LED. Select a Clear RGB Led Colour block and snap it underneath.

The completed starter code blocks

Run it and test

We have now completed all the code that we need. The next thing to do is test it and make sure it works as expected.

Hit the Run button at the top of the code area to start the PicoBricks.
You will see the startup message on the OLED display telling you to press the button to start.
Press the button to start setting the timer.
Turn the potentiometer to choose the number of hours.
Press the button to lock in the hours and move to minutes.
Turn the potentiometer to choose the number of minutes.
Press the button to lock in the minutes and move to seconds.
Turn the potentiometer to choose the number of seconds.
Press the button to lock in the seconds and start the countdown.
When the timer reaches zero, the buzzer sounds and the LED and RGB LED light up.
Press the button to stop the alarm.

⏰

You have built your own countdown timer with PicoBricks. Brilliant work!

Try it yourself

Challenge: Can you make the alarm more exciting? Try changing the buzzer frequency so it plays a little tune when the timer reaches zero, or make the RGB LED flash through different colours instead of staying on one.

For an extra challenge, add a message on the screen that says Time's up! when the countdown finishes.

Stuck? Quick fixes

Problem	Try this
Nothing appears on the OLED screen	Check the screen module is connected properly, and make sure you've added a `Show Screen Buffer` block after writing your text. Without it, the screen stays blank.
The timer won't start when I press the button	Make sure the button module is connected. Remember you need to press the button to set the hours, minutes and seconds before the countdown begins.
The numbers don't change when I turn the dial	Check the potentiometer is connected, and double-check you used a `Read Potentiometer` block in your hour, minutes and seconds functions.
My code won't upload to the PicoBricks	Check the USB cable is plugged in, then press the connection button at the top of the editor to pair the Raspberry Pi Pico again.
The buzzer doesn't sound at zero	Make sure the buzzer module is connected, and check your `control` function includes the `Play Buzzer Freq` block.