Pico Alarm Clock

Introduction

This is an alarm clock that is running on Raspberry Pi Pico and is displaying on a TM1637 7-segment display. In this project I try to stay close to the hardware and implement what I can from scratch. For example, I wrote my own library for the display and I use real hardware interrupts for button clicks and time based events.

I made a short YouTube video showing some of the functionallity of the clock.

Dependencies

• Raspberry Pi Pico SDK: The standard library for working with Pico.
• Pico Extras: Some additional libraries. I needed this for putting the Pico in sleep mode.
• TM1637-pico: My own library for writing to the 7-segment display.

Setup

Hardware

• Raspberry Pi Pico
• TM1637 7-segment display
• Passive buzzer
• 3 Buttons
• Led (I used a yellow one)
• 4 Resistors: 3 for button debouncing (1k) and 1 for the LED (2k). Exact sizes are not important and might vary depending on the buttons and LED.
• 3 Ceramic capacitors (100 nF) for button debouncing.
• A micro USB power cable and 5V power supply.

Circuit

Load Code

A .elf and .uf2 binary can be downloaded for 1.0 or later. You can also clone the repository and build from source. Then the files will apear in the build/src directory.

UF2

Hold down the bootsel button and plug Rasperry Pi Pico into a USB port on your computer (Windows or Linux). The Pico will mount as a USB Mass Storage Device. Drag and droop the .uf2 file on the Pico.

ELF

The .elf file can be loaded to the pico over UART. This is most easily done from a Rasperry Pi (computer), but can also be done with another Pico using Picoprobe. See Getting started with Raspberry Pi Pico: Appendix A

If loading code over UART (from for example a Raspberry Pi) some unexpected behavior arises.

The openocd reset command does not work with this code. I don't know why but a workaround is to remove that from the command. Load code with: openocd -f interface/raspberrypi-swd.cfg -f target/rp2040.cfg -c "program src/alarm-clock.elf verify exit" Then restart the Pico manually by using a reset switch or un- and re-plugging the power.

Usage

Under normal circumstances will the display show current time and wait for alarms to fire. When the clock is turned on the time will be Monday 00:00:00 and there is no set alarms. To change the time or add an alarm, open the menu.

The Settings Menu

If any button is pressed the menu will open. In the menu you can change the display brightness, set clock time and set alarms. See the flowchart below for a quick overview or read the following sections for an in-depth description.

Brightness

In the brightness state the display will show br: x, where x will change with the brightness level. In- or decrease the brightness with the M and R buttons. The brightness has 8 levels, ranging from 0 to 7. Although there seems to be a very little change in brightness in the higher levels.

Set Clock

To enter Set Clock press the R button when the display shows SEt. Here you can change the running clock.

• Day of the week (da:xx): In or decrease with the M and R buttons. A list of the days and their two letters:
  • Monday: mo
  • Tuesday: tU
  • Wednesday: wE
  • Thursday: tH
  • Friday: Fr
  • Saturday: SA
  • Sunday: SU
• Hour (Hr:xx): In- or decrease with the M and R buttons.
• Minute (mi:xx): In- or decrease with the M and R buttons.
• Seconds (SE:xx): Zero the counter with the M or R button. Please note that this only sets the current second to 0, it doesn't restart the RTC. This makes it impossible to set exactly when a second starts.
• Done (done): Go back to the main menu.

Alarms

To enter Alarms press the R button when the display shows ALAr. Then you will be navigated to the first alarm, called AL: 0. Given that this alarm exists. Otherwise you will see nEw on the display.

To create a new alarm, navigate to nEw and press R. That will open the edit state for a new alarm.

To edit an existing alarm, navigate to AL: x and press R.

Editing an alarm works a lot like setting the clock. With some differences:

• You can not specify seconds
• Song (So). This is what sound the alarm will make. Use the R button to increment song and M button to listen to it.
• Activate (Act): Toggle active status of this alarm. The LED will be on if the alarm is on and off if the alarm is off. When creating a new alarm is it by default on.
• Delete (dEL): Exit and delete the current alarm. Confirm deletion with R, abort with L or M.
• Done (done): Will fail if there already is an alarm with the same time.

Note that when exiting from done, you will always get to the first alarm AL: 0. This is because the list of alarms will always be in chronological order, and might need rearrangement after an edit.

To delete an alarm, navigate to it and press M. Then press R. To abort press any other button.

The Alarms

You can have an unlimited numbers of alarms. Every alarm has a time (specified by day of the week, hour and minute), a song (what tones will play when it fires) and an active status. To change these see this section.

When an alarm fires it will play it's song and blink the LED. It will continue until any button is pressed to stop it or the max duration has passed (default 5 minutes).

Making modifications

If you want to make some modifications to the program i would recommend starting with these files.

• pins.h: Here you can change what physical pin will have what function. So if your prototype does not have the same connections as mine you need to make changes here.
• timout_timer.h: Here you will find ALARM_TIMEOUT which determines for how long an alarm should fire before turning off automatically.
• song_def.c: Here the songs (alarm sounds) are defined. You can edit, add and remove songs. Please note that what tones that resonates best depends on your buzzer, so this might be necessary if you have a very different one from mine.