CALalarm

There is no better feeling than not having to set an alarm

ESP32 OLED alarm clock that syncs with Google Calendar.

Features:

Shows the time and first event of the day.
Learns the alarm time from Google Calendar.
Piezo and/or haptic to wake you up.
Button stops the noise.
Open source!

Software

Clone the repository and its submodules to a local directory. The --recursive flag automatically initializes and updates the submodules in the repository. Start with a fresh clone, and copy the Kconfig.example.

git clone https://github.com/cvonk/CALalarm.git
cd CALalarm/alarm
cp alarm/main/Kconfig.example alarm/main/Kconfig
cp factory/main/Kconfig.example factory/main/Kconfig

Google Apps Script

The software is a symbiosis between Google Apps Script and firmware running on the ESP32. The script reads the alarm event from your Google Calendar and presents it as JSON to the ESP32 device.

To create the Web app:

Create a new project on script.google.com;
Rename the project to e.g. CALalarm_doGet
Copy and paste the code from script\Code.js
Add the Google Calendar API service .
Select the function test and click Debug. This will ask for permissions. There will not be any output.
Click Deploy and chose New deployment, choose
- Service tye = Web app
- Execute as = Me
- Who has access = Anyone, make sure you understand what the script does!
- Copy the Web app URL to the clipboard

Open the URL in a web browser. You should get a reply like

{
    "time": "2022-04-20 13:18:37",
    "pushId": "some_id_or_not",
    "events": [
        { 
            "alarm": "2022-04-20 08:05:00",
            "start": "2022-04-20 08:35:00",
            "end": "2022-04-20 15:45:00",
            "title": "School"
        },
    ]
}

Then, paste the URL to alarm/main/Kconfig as the value of CALALARM_GAS_CALENDAR_URL.

As we see in the next sections, the ESP32 does a HTTP GET on this URL, to retrieve a list of upcoming events from your calendar.

ESP32 Device

In menuconfig, scroll down to CALalarm and select "Use hardcoded Wi-Fi credentials" and specify the SSID and password of your Wi-Fi access point.

idf.py set-target esp32
idf.py menuconfig
idf.py flash

Hardware

⚠️ THIS PROJECT IS OFFERED AS IS. IF YOU USE IT YOU ASSUME ALL RISKS. NO WARRENTIES.

Schematic

Haptic motor M1 draws 100 mA at 5 Volts. The GPIO "on" voltage of the ESP32 is typically 3.1 Volt and can supply up to 20 mA. To drive the PN2222A transistor to saturation, we need a V_be = 0.6 Volt. This implies that for I_b of 2.5 mA, the base resistor R3 should be 1 kΩ. Note that, diode D1 protects for reverse back current due to the motor inductance.

The piezo buzzer X1, when driven with a 5 V_pp 1 kHz square wave, also draws 100 mA. That implies that the base resistor R1 should be 1 kΩ as well. We use resistor R2, to discharge the capacitive piezo element, as specified in the datasheet.

For the phototransistor Q1, the value for the current limiting resistor R4 is taken from the test setup in its datasheet.

Bill of materials

Name	Description	Sugggested mfr/part#
PCB1	Feather Huzzah32 ESP32 (ESP-WROOM32)	Adafruit 3619
PCB2	FeatherWing OLED, 128x32	Adafruit 2900
PROTO	FeatherWing prototyping add-on	Adafruit 2884
M1	Vibrating mini motor disc, 5V	Adafruit 1201
X1	Piezo buzzer 5V AC, through hole	Adafruit 160 or TDK PS1240P02BT
T1, T2	NPN transistor, 40V / 600mA, TO92-3	NTE Electronics PN2222A
Q1	Phototransistor, HW5P-1	Adafruit 2831
D1	Diode, general purpose, 100V / 200mA, DO35	onsemi 1N4148
R1 - R4	Resistor, 1 kΩ, 1/4 W, axial	Yageo CFR-25JT-52-1K