View raw code<\/a><\/p>\n\n\n\nHow the Code Works<\/h3>\n\n\n\n Let\u2019s take a quick look at the relevant parts of this code.<\/p>\n\n\n\n
Import Libraries<\/h4>\n\n\n\n First, you need to import the urtc<\/span> module you\u2019ve uploaded previously that contains the functions to interact with the RTC. You also need to import the Pin<\/span> and I2C<\/span> classes to establish an I2C communication with the module.<\/p>\n\n\n\nimport time\nimport urtc\nfrom machine import I2C, Pin<\/code><\/pre>\n\n\n\nInitialize the RTC Module<\/h4>\n\n\n\n Then, initialize I2C communication and create an object called rtc<\/span> to refer to our DS3231 RTC module.<\/p>\n\n\n\n# Initialize RTC (connected to I2C)\ni2c = I2C(0, scl=Pin(5), sda=Pin(4))\nrtc = urtc.DS3231(i2c)<\/code><\/pre>\n\n\n\nSynchronize the Time<\/h4>\n\n\n\n To synchronize the RTC time, you must use the datetime()<\/span> method on the rtc<\/span> object and pass as an argument a time tuple with the following format:<\/p>\n\n\n\n(year, month, day, day of week, hour, minute, seconds, milliseconds)<\/code><\/pre>\n\n\n\nNote:<\/strong> this tuple is different from the one used by the MicroPython time<\/span> module.<\/p>\n\n\n\nWe can set the time manually to a defined date and time as follows:<\/p>\n\n\n\n
#initial_time = (2024, 1, 30, 1, 12, 30, 0, 0)<\/code><\/pre>\n\n\n\nOr, we can synchronize the RTC with the system\u2019s local time. We’ll synchronize the time with the system’s local time.<\/p>\n\n\n\n
First, we get the time tuple of the local time using time.localtime()<\/span>.<\/p>\n\n\n\ninitial_time_tuple = time.localtime() # tuple (microPython)<\/code><\/pre>\n\n\n\nThe tuple returned is different from the one used by the urtc<\/span> module.<\/p>\n\n\n\nSo, first, we convert it to seconds using time.mktime()<\/span>.<\/p>\n\n\n\ninitial_time_seconds = time.mktime(initial_time_tuple) # local time in seconds<\/code><\/pre>\n\n\n\nAnd finally, we convert it to a tuple that is compatible with the library using the seconds2tuple()<\/span> function from the urtc<\/span> library that accepts as an argument the number of seconds since epoch for the local time.<\/p>\n\n\n\ninitial_time = urtc.seconds2tuple(initial_time_seconds)<\/code><\/pre>\n\n\n\nFinally, we can pass our initial_time<\/span> variable that contains the local time in a tuple compatible with the urtc<\/span> module to the datetime()<\/span> function as follows.<\/p>\n\n\n\n# Convert to tuple compatible with the library\ninitial_time = urtc.seconds2tuple(initial_time_seconds)\n\n# Sync the RTC\nrtc.datetime(initial_time)<\/code><\/pre>\n\n\n\nNote: <\/strong> After setting the time for the first time, we only need to set the time again if the RTC loses power (you should have a battery connected to prevent this). You can use the lost_power()<\/span> function on the rtc<\/span> object to check if it has lost power. This function returns True<\/span> or False<\/span> accordingly.<\/p>\n\n\n\nGetting the Time<\/h4>\n\n\n\n After these lines of code, the RTC module is synchronized with your local time and you can simply call rtc.datetime()<\/span> to get the current time from the RTC. This returns an object with all the time elements.<\/p>\n\n\n\nTo get and print each time element, we can do as follows:<\/p>\n\n\n\n
current_datetime = rtc.datetime()\nprint('Current date and time:')\nprint('Year:', current_datetime.year)\nprint('Month:', current_datetime.month)\nprint('Day:', current_datetime.day)\nprint('Hour:', current_datetime.hour)\nprint('Minute:', current_datetime.minute)\nprint('Second:', current_datetime.second)\nprint('Day of the Week:', days_of_week[current_datetime.weekday])<\/code><\/pre>\n\n\n\nWe can also get the current temperature from the module by calling the get_temperature()<\/span> method on the rtc<\/span> object.<\/p>\n\n\n\ntemperature = rtc.get_temperature()<\/code><\/pre>\n\n\n\nThe temperature data comes in Celsius degrees.<\/p>\n\n\n\n
print(f\"Current temperature: {temperature}\u00b0C\")<\/code><\/pre>\n\n\n\nWe print the time and current temperature every second.<\/p>\n\n\n\n
time.sleep(1)<\/code><\/pre>\n\n\n\nRun the Code<\/h3>\n\n\n\n Run this previous code to synchronize the RTC time with the local time, and get the current time and temperature.<\/p>\n\n\n
\n
From now on, if the RTC has an attached battery, it will keep the time synchronized with your local time. So, you don\u2019t need to synchronize it anymore, and you can just call rtc.datetime()<\/span> to get the current time.<\/p>\n\n\n\n
DS3231 with the Raspberry Pi Pico – Setting Alarms<\/h2>\n\n\n\n The DS3231 RTC Module allows you to set up to two alarms: alarm 1 and alarm 2. When the time reaches the alarm time, the module changes the state of the SQW pin from HIGH to LOW (it is active low). We can check for the change on that pin and perform a certain task when the alarm fires.<\/p>\n\n\n
\n
Important notes about the alarms:<\/p>\n\n\n\n
\nthe RTC allows you to save up to two alarms;<\/li>\n\n\n\n you can only have one alarm active at a time;<\/li>\n\n\n\n after an alarm is triggered, you must clear its flag to avoid triggering and crashing the Pico;<\/li>\n\n\n\n you must deactivate an alarm before activating the other.<\/li>\n<\/ul>\n\n\n\nDS3231 – Setting Up the Alarms<\/h3>\n\n\n\n The following example shows how to set up two alarms. It toggles an LED when the alarm fires. To test this example, add an LED with a 220 Ohm resistor to the circuit. Connect the LED to GPIO 2.<\/p>\n\n\n
# Rui Santos & Sara Santos - Random Nerd Tutorials\n# Complete project details at https:\/\/RandomNerdTutorials.com\/raspberry-pi-pico-ds3231-rtc-micropython\/\n\nimport time\nimport urtc\nfrom machine import Pin, I2C\n\n# Pin setup for SQW pin and LED\nCLOCK_INTERRUPT_PIN = 3 # Adjust to your specific GPIO pin for SQW\nLED_PIN = 2 # Adjust to your specific GPIO pin for the LED\n\n# Initialize RTC (connected to I2C)\ni2c = I2C(0, scl=Pin(5), sda=Pin(4))\nrtc = urtc.DS3231(i2c)\n\n# Setup GPIO for SQW and LED\nsqw_pin = Pin(CLOCK_INTERRUPT_PIN, Pin.IN, Pin.PULL_UP)\nled_pin = Pin(LED_PIN, Pin.OUT)\nled_pin.off()\n\n# Alarm times (year, month, day, weekday, hour, minute, second, millisecond)\nalarm1_time = urtc.datetime_tuple(2025, 01, 04, None, 12, 32, 00, 0) # Alarm 1 uses full datetime\nalarm2_time = urtc.datetime_tuple(2025, 01, 04, None, 12, 35, 00, 0) # Alarm 2 uses day, hour, minute, weekday\n\n# Print the current time from the RTC\ndef print_current_time():\n now = rtc.datetime()\n formatted_time = f"{now.year}-{now.month:02}-{now.day:02} {now.hour:02}:{now.minute:02}:{now.second:02}"\n print(f"Current time: {formatted_time}")\n\n\n#Callback for handling alarm interrupt.\ndef on_alarm(pin):\n print("Interrupt detected.")\n \n if rtc.alarm(alarm=0): # Check if Alarm 1 triggered\n print("Alarm 1 triggered.")\n rtc.alarm(False, alarm=0) # Clear Alarm 1 flag\n led_pin.value(not led_pin.value()) # Toggle LED for Alarm 1\n \n if rtc.alarm(alarm=1): # Check if Alarm 2 triggered\n print("Alarm 2 triggered.")\n rtc.alarm(False, alarm=1) # Clear Alarm 2 flag\n led_pin.value(not led_pin.value()) # Toggle LED for Alarm 2\n\n# Setup alarms on the DS3231\ndef setup_alarms():\n # Clear any existing alarms\n rtc.alarm(False, 0)\n rtc.alarm(False, 1)\n rtc.no_interrupt()\n\n # Set the desired alarm times\n rtc.alarm_time(alarm1_time, 0) # Alarm 1\n rtc.alarm_time(alarm2_time, 1) # Alarm 2\n\n # Enable interrupts for the alarms\n rtc.interrupt(0)\n rtc.interrupt(1)\n print("Alarms set successfully.")\n\n\n# Attach the interrupt callback\nsqw_pin.irq(trigger=Pin.IRQ_FALLING, handler=on_alarm)\n\ntry:\n # Sync time to compile time if RTC lost power\n if rtc.lost_power():\n initial_time_tuple = time.localtime() # tuple (MicroPython)\n initial_time_seconds = time.mktime(initial_time_tuple) # local time in seconds\n initial_time = urtc.seconds2tuple(initial_time_seconds) # Convert to tuple compatible with the library\n rtc.datetime(initial_time) # Sync the RTC\n\n print("RTC initialized. Setting alarms...")\n setup_alarms()\n\n while True:\n print_current_time()\n time.sleep(5)\nexcept KeyboardInterrupt:\n print("Exiting program.")\n<\/code><\/pre>\n\tView raw code<\/a><\/p>\n\n\n\nHow Does the Code Work?<\/h3>\n\n\n\n Let’s take a look at the relevant parts of code to set up the alarms.<\/p>\n\n\n\n
Defining the Pins<\/h4>\n\n\n\n First, you need to define the GPIO that is connected to the SQW pin. This is the pin that will change state when the alarms fire. We chose to connect it to GPIO 3, but you can choose any other pins as long as the circuit connections match.<\/p>\n\n\n\n
CLOCK_INTERRUPT_PIN = 3 # Adjust to your specific GPIO pin for SQW<\/code><\/pre>\n\n\n\nWe set the SQW pin as an input with an internal pull-up resistor (because it is an active-low pin).<\/p>\n\n\n\n
sqw_pin = Pin(CLOCK_INTERRUPT_PIN, Pin.IN, Pin.PULL_UP)<\/code><\/pre>\n\n\n\nAlarm Times<\/h4>\n\n\n\n Then, we create two variables of type datetime_tuple<\/span> to save the alarm times in variables as follows:<\/p>\n\n\n\n# Alarm times (year, month, day, weekday, hour, minute, second, millisecond)\nalarm1_time = urtc.datetime_tuple(2025, 01, 04, None, 12, 32, 00, 0) # Alarm 1 uses full datetime\nalarm2_time = urtc.datetime_tuple(2025, 01, 04, None, 12, 35, 00, 0) # Alarm 2 uses day, hour, minute, weekday<\/code><\/pre>\n\n\n\nAdjust the alarms to your desired times.<\/p>\n\n\n\n
Setting the SQW Pin as an Interrupt<\/h4>\n\n\n\n Then, we set the SQW pin as an interrupt by calling the irq()<\/span> method. <\/p>\n\n\n\nsqw_pin.irq(trigger=Pin.IRQ_FALLING, handler=on_alarm)<\/code><\/pre>\n\n\n\nThe irq()<\/span> method accepts the following arguments:<\/p>\n\n\n\n\nhandler:<\/strong> this is a function that will be called when an interrupt is detected, in this case the on_alarm()<\/span> function.<\/li>\n\n\n\ntrigger:<\/strong> this defines the trigger mode. There are 3 different conditions. In our case, we’ll use IRQ_FALLING<\/span> to trigger the interrupt whenever the pin goes from HIGH to LOW.<\/li>\n<\/ul>\n\n\n\n\n
To learn more about setting interrupts with the Raspberry Pi Pico using MicroPython, check the following tutorial:<\/p>\n\n\n\n
![\"Raspberry](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2025\/01\/Raspberry-Pi-Pico-DS3231-Micropython.jpg?resize=1200%2C675&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\n![\"RTC](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2024\/12\/RTC3231-DS1307-RTC-Modules.jpg?resize=750%2C422&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\n![\"RTC](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2024\/12\/RTC-DS32321-Module.jpg?resize=750%2C422&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\n![\"RTC](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2024\/12\/RTC-DS32321-Module-back.jpg?resize=750%2C422&quality=100&strip=all&ssl=1\")
<\/figure>\n<\/div>\n\n\n\n![\"DS3231](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2024\/12\/RTC-DS3231-Battery-Holder.jpg?resize=750%2C422&quality=100&strip=all&ssl=1\")
<\/figure>\n<\/div>\n<\/div>\n\n\n\n![\"RTC](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2024\/12\/RTC-DS32321-remove-resistor-for-nor-rechargeable-battery.jpg?resize=750%2C422&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\n![\"Wiring](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2025\/01\/RPi-Pico-DS3231-Wiring.jpg?resize=750%2C422&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\n![](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2017\/10\/header-200.png?w=1200&quality=100&strip=all&ssl=1\")
<\/a><\/p>\n\n\n\n![\"RPi](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2025\/01\/RPi-Pico-DS3231-Set-and-Get-Time.jpg?resize=750%2C422&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\n![\"Run](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2023\/12\/thonny-ide-run-button.png?resize=470%2C114&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\n![\"Raspberry](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2025\/01\/RPi-Pico-DS3231-set-Get-Time-Testing.png?resize=800%2C352&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\n![\"Raspberry](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2025\/01\/RPi-Pico-DS3231-Settings-Alarms.jpg?resize=750%2C422&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\n