1 - Clocks

The core function of a watch is telling time. All of the watch faces in this category tell time in one form or another.

Simple Clock

The Simple Clock watch face echoes the classic time and date display of the stock F-91W. It displays the day of the week and day of the month on the top line, along with the current time on the bottom line. Pressing the Light button illuminates the LED so that you can read the display in the dark. Holding the Light button keeps the LED on while the button is held.

If you soldered the buzzer connector to your Sensor Watch board, you may also toggle the Hourly Chime feature by pressing and holding the Alarm button. When you release the Alarm button, the Signal indicator will turn on, indicating that the hourly chime is enabled.

The Simple Clock face also incorporates a low battery warning: this watch face will display the LAP indicator when it detects that the battery voltage is low. This does not mean that power failure is imminent, but it does mean that your battery has only about 5% of its original capacity remaining and you should start thinking about a replacement. The battery is a CR2016 coin cell.

World Clock

The World Clock watch face looks similar to the Simple Clock watch face, but you’ll notice that at first launch the day of week indicators are blank. That’s because this watch face does not display the day of the week. Instead, you may customize these letters to display the name of a time zone of your choosing.

To customize this watch face, press and hold the Alarm button. The first letter in the top row will begin flashing. Press the Alarm button repeatedly to advance through the available letters in the first slot, then press the Light button to move to the second letter. Finally, press Light again to move to the time zone setting, and press Alarm to cycle through the available time zones. Press Light one last time to return to the world clock display.

Note that the second slot cannot display all letters or numbers. Also note that at this time, time zones do not automatically update for daylight saving time; you will need to manually adjust this field each spring and fall.

Beat Time

The Beat Time face displays the current Swatch Internet Time, or .beat time. This is a decimal time system that divides the day into 1000 beats.

The three large digits in the bottom row indicate the current beat, and the two smaller digits (normally the seconds in Simple Clock) indicate the fractional beat; so for example you can read “67214” as “beat 672.14”.

Mars Time

This watch face is dedicated to Martian timekeeping. It has several modes, and can display either a time or a date. Pressing the Alarm button cycles through different time zones on Mars:

  • MC - Mars Coordinated Time, the time at Airy-0 Crater on the Martian prime meridian
  • ZH - Local mean solar time for the Zhurong rover
  • PE - LMST for the Perseverance rover
  • IN - LMST for the Insight lander
  • CU - LMST for the Curiousity rover

Press the Light button to toggle between displaying time and date:

  • MC S - the Mars Sol Date, Martian days since December 29, 1873
  • ZH Sol - Mission sol for the Zhurong rover
  • PE Sol - Mission sol for the Perseverance rover
  • IN S - Mission sol for the InSight lander
  • CU S - Mission sol for the Curiousity rover

Note that where the mission sol is below 1000, this watch face displays the word “Sol” on the bottom line. When the mission sol is over 1000, the word “Sol” will not fit and so it displays a stylized letter S at the top right.

2 - Complications

In horology, a complication is an additional set of gears in a mechanical watch movenent that enables a secondary function, such as a sunrise/sunset dial. The watch faces in this category do just that.


This watch face displays local sunrise and sunset times. During the day, it displays today’s sunset; at night, it displays tomorrow’s sunrise.

When you first see this watch face, it will display “No Loc”, or No Location. This is because your latitude and longitude are required to calculate sunrise and sunset. When on this screen, you can set your location in a similar way to the World Clock screen.

Press and hold Alarm to enter location setting mode. The top line will read “LA” (Latitude), and the bottom line “+ 0000”. The large digits are the whole number part of the latitude, and the smaller digits (in the seconds place) are the fractional part. Enter your latitude and longitude (“LO”) by pressing the Alarm button to change the sign or advance the digits, and the Light button to move to the next character; for example, a latitude of 40.73° N would be “+ 4073”, and a longitude of 73.94° W would be “–07394”.

Once you have set your latitude and longitude, the Sunrise/Sunset face will display the next sunrise or sunset on the bottom row, and the day of that sunrise or sunset at the top right.

A short press on the Alarm button will advance to the following sunrise or sunset: for example, on Monday afternoon, it will display Monday evening’s sunset, but a short press on the Alarm button will display Tuesday morning’s sunrise.

If you made a mistake while entering your location, or if you simply wish to change your location, you can re-enter location setting mode with another long press on the Alarm button.

Moon Phase

The Moon Phase face is similar to the Sunrise/Sunset face: it displays the current phase of the moon, along with the day of the month and a graphical representation of the moon on the top row.

This graphical representation is a bit abstract. The segments that turn on represent the shape of the moon, waxing from the bottom right and waning at the top left. A small crescent at the bottom right will grow into a larger crescent, then add lines in the center for a quarter and half moon. All segments are on during a full moon. Then gradually the segments at the bottom right will turn off, until all that remains is a small waning crescent at the top left.

All segments turn off during a new moon.

On this screen you may press the Alarm button repeatedly to move forward in time: the day of the month at the top right will advance by one day for each button press, and both the text and the graphical representation will display the moon phase for that day. Try pressing the Alarm button 27 times now, just to visualize what the moon will look like over the next month.








The Pulsometer is an implementation of a sort of a classic mechanical watch complication. A classic pulsometer complication involves a chronograph with a scale calibrated for counting a certain number of heartbeats (often 30). You start it and begin counting heartbeats, and stop it after counting the specified number of beats. Once stopped, the needle will point to your heart rate.

The pulsometer on Sensor Watch flashes its instructions at launch: “Hold Alarm + count 30 beats.” Using the hand on the side where you wear your watch, touch your carotid artery (in your neck) and feel for your pulse. Once you find it, use your other hand to press and hold the Alarm button, and count your heartbeats. When you reach 30 beats, release the Alarm button. The display will show a number such as “60 bpm”; this is your heart rate in beats per minute.

Two notes:

  1. For the first few seconds of a measurement, the display will read “Hi”. This indicates that it’s too early for the measured value to be a valid heart rate. Once the measurement is below 240 bpm, the display will update.
  2. If you hold the button down for more than 45 seconds, the display will read “Lo”. If it took this long for you to count 30 heartbeats, this indicates that your heart rate is below 40 beats per minute.

Tomato Productivity Timer


TOTP Generator

This watchface generates time based one time passwords (two factor auth codes) allowing you to sign in securely to many popular websites (e.g. Google, Github). Time-based one-time password (TOTP) is a computer algorithm that generates a one-time password (OTP) that uses the current time as a source of uniqueness.

Press the Alarm button to cycle between your configured websites / TOTP secrets.

The watchface supports multiple websites / TOTP secrets, which need to be extracted from TOTP QR codes and added to the source code for the watchface as follows:

  1. Obtain a TOTP secret or QR ode from the website you want to generate codes for.
  2. If you have just the QR code, Stefan Sundin’s web site will allow you to extract the secret - it will be an alphanumeric string around 32 characters long, which is the TOTP secret encoded in Base32.
  3. To add the secret to the watchface code, you need to convert it to hexadecimal bytes. This cryptii.com page will allow you to do that conversion. Note you’ll have to enter your TOTP secret in uppercase. Shell tools can be used to convert secret to bytes:
  1. Finally, you’ll need to take the Hexadecimal bytes and add them to the TOTP watchface source code and recompile movement:

Edit totp_face.c

You may want to remove the demo keys. Assuming you want to add a key to the end of the list:

static const uint8_t num_keys = 2;

Add one to the number on this line.

static uint8_t keys[] = {
   // Add the hex bytes for your key

Add the hexadecimal bytes from step 3 to the end of this array, comma separated and each one preceeded by 0x. Don’t forget to add a comma after the previous final byte.

static const uint8_t key_sizes[] = {

Add the size of your secret (the number of hex bytes you just added) to the end of this array.

static const uint32_t timesteps[] = {

Add another 30 entry to the end of this array.

static const char labels[][2] = {

Add a label for your secret… E.g. if it’s for your Google account you might want to add { 'g', 'o' } as a friendly label.

That’s it - enjoy the convenience of TOTP codes on your wrist!

Day One

This watch face displays the number of days since a given date. It was originally designed to display the number of days you’ve been alive, but technically it can count up from any date in the 20th century or the 21st century, so far.

Long press on the Alarm button to enter customization mode. The text “YR” will appear, and will allow you to set the year starting from 1959. Press Alarm repeatedly to advance the year. If your birthday is before 1959, advance beyond the current year and it will wrap around to 1900. Once you have set the year, press Light to set the month (“MO”) and day (“DA”), advancing the value by pressing Alarm repeatedly.

Note that at this time, the Day One face does not display the sleep indicator in sleep mode, which may make the watch appear to be unresponsive in sleep mode. You can still press the Alarm button to wake the watch. This UI quirk will be addressed in a future update.

Blinky Light

The blinky light watch face was designed as a tutorial for making a watch face in Movement, but it actually might be useful to have a blinking light in a pinch.

The screen displays the name of the watch face (”BL”), as well as an S at the top right for slow blink or an F for fast blink. The bottom line selects the color: green, red or yellow. You can change the speed of the blinking light by pressing the Alarm button, and change the color with the Light button. A long press on the Alarm button starts the blinking light, and another long press stops it.

Note that this will chew through your battery! The green LED uses about 450µA at full brightness, which is 45 times the normal power consumption of the watch. The red LED is an order of magnitude less efficient (4500 µA), and the yellow setting lights both LEDs, which chews through nearly 5 milliamperes. This means that one hour of yellow blinking is likely to eat up between 2 and 3 percent of the battery’s usable life! Still, if you need to signal your location to someone in a dark forest, this watch face could come in handy.

Just try to use the green LED as much as you can.


The Astronomy watch face is among the most complex watch faces in the Movement collection. It allows you to calculate the locations of celestial bodies in the sky, as well as distance in astronomical units (or, in the case of the Moon, distance in kilometers).

When you arrive at the Astronomy watch face, you’ll see its name (“Astro”) and an animation of two objects orbiting each other. You will also see “SO” (for Sol) flashing in the top left. The flashing letters indicate the currently selected celestial body. Short press Alarm to advance through the available celestial bodies:

  • SO - Sol, the sun
  • ME - Mercury
  • VE - Venus
  • LU - Luna, the Earth’s moon
  • MA - Mars
  • JU - Jupiter
  • SA - Saturn
  • UR - Uranus
  • NE - Neptune

Once you’ve selected the celestial body whose parameters you wish to calculate, long press the Alarm button and relase it. The letter “C” will flash while the calculation is performed.

When the calculation is complete, the screen will display the altitude (“aL”) of the celestial body. You can cycle through the available parameters with repeated short presses on the Alarm button:

  • aL - Altitude (in degrees), the elevation over the horizon. If negative, it is below the horizon.
  • aZ - Azimuth (in degrees), the cardinal direction relative to true north.
  • rA - Right Ascension (in hours/minutes/seconds)
  • dE - Declination (in degrees/minutes/seconds)
  • di - Distance (the digits in the top right will display either aU for astronomical units, or K for kilometers)

Long press on the Alarm button to select another celestial body.


The Orrery watch face is similar to the Astronomy watch face in that it calculates properties of the planets, but instead of calculating their positions in the sky, this watch face calculates their absolute locations in the solar system. This is only useful if you want to plot the planets on graph paper, but hey, you never know!

The controls are identical to the Astronomy watch face: while the title screen (“Orrery”) is displayed, you can advance through the available planets with repeated short presses on the Alarm button. The available planets:

  • ME - Mercury
  • VE - Venus
  • EA - Earth
  • LU - Luna, the Earth’s moon
  • MA - Mars
  • JU - Jupiter
  • SA - Saturn
  • UR - Uranus
  • NE - Neptune

Note that the sun is not available in this menu, as the sun is always at (0,0,0) in this calculation.

Long press on the Alarm button to calculate the planet’s location, and after a flashing “C” (for Calculating), you will be presented with the planet’s X coordinate in astronomical units. Short press Alarm to cycle through the X, Y and Z coordinates, and then long press Alarm to return to planet selection.

The large numbers represent the whole number part, and the two smaller numbers (in the seconds place) represent the decimal portion. So if you see “SA X 736” and “SA Y -662”, you can read that as an X coordinate of 7.36 AU and a Y coordinate of -6.62 AU. You can literally draw a dot at (0, 0) to represent the sun, and a dot at (7.36, -6.62) to represent Saturn. (the Z coordinates tend to be pretty close to zero, as the planets largely orbit on a single plane, the ecliptic)

3 - Demo Faces

These watch faces demonstrate functionality of the watch, and aren’t generally watch faces you’d build into a working firmware.

Character Set

This watch face displays all of the characters in the Sensor Watch character set. You can advance from one character to the next with a short press of the Alarm button.

This watch face may be useful to watch face developers, in that it can help them to understand which characters will work in different positions.


This watch was designed for the Crowd Supply marketing team, so they could photograph the various functions of Sensor Watch. The Alarm button advances through static screens that simulate different watch faces.

This watch face may only be useful to you if you need to photograph Sensor Watch, i.e. for a blog post.

4 - Sensors

Sensor Watch is designed to display data from sensors. The watch faces in this category read sensor data and present it in a useful way.


This watch face is very simple and has no controls to speak of. It displays the battery voltage as measured by the SAM L22’s ADC.

Note that the Simple Clock watch face includes a low battery warning, so you don’t technically need to this watch face unless you want to track the battery level.

Temperature Display

This watch face is designed to work with either the Temperature + GPIO sensor board or the Temperature + Light sensor board. It reads the current temperature from the thermistor voltage divider on the sensor board, and displays the current temperature in degrees Celsius.

When the watch is on your wrist, your body heat interferes with an ambient temperature reading, but if you set it on a bedside table, strap it to your bike handlebars or place it outside of your tent while camping, this watch face can act as a digital thermometer for displaying ambient conditions.

The temperature sensor watch face automatically samples the temperature once every five seconds, and it illuminates the Signal indicator just before taking a reading.

Pressing the Alarm button toggles the unit display from Celsius to Fahrenheit. Technically this sets the global “Metric / Imperial” flag, so any other watch face that displays localizable units will display them in the system selected here.

Temperature Log

This watch face automatically logs the temperature once an hour, and maintains a 36-hour log of readings. This watch face is admittedly rather complex, and bears some explanation.

The main display shows the letters “TL” in the top left, indicating the name of the watch face. At the top right, it displays the index of the reading; 0 represents the most recent reading taken, 1 represents one hour earlier, etc. The bottom line in this mode displays the logged temperature.

A short press of the “Alarm” button advances to the next oldest reading; you will see the number at the top right advance from 0 to 1 to 2, all the way to 35, the oldest reading available.

A short press of the “Light” button will briefly display the timestamp of the reading. The letters at the top left will display the word “At”, and the main line will display the timestamp of the currently displayed data point. The number in the top right will display the day of the month for the given data point; for example, you can read “At 22 3:00 PM” as ”At 3:00 PM on the 22nd”.

If you need to illuminate the LED to read the data point, long press the Light button and release it.

Temperature Testing

This watch face is similar to the Temperature watch face, but it updates the temperature several times per second. You likely don’t need this watch face, but it is useful for testing the temperature sensor boards.

LIS2DW Accelerometer Data Logger

This is an experimental watch face for logging data on the “Sensor Watch Motion Express” board. I will add more documentation for this watch face once this sensor board is more widely available.

5 - Settings

The watch faces in this section relate to watch configuration.


The Preferences watch face allows you to configure various options on your Sensor Watch. Like all other screens, you advance the field you’re setting with the Light button, and advance its value with the Alarm button. The Preferences watch face labels each setting with a two-letter code on the top row; the following list describes each setting and their options:

CL - Clock mode. This setting allows you to select a 12-or 24-hour clock display. All watch faces that support displaying the time will respect this setting; for example, both Simple Clock, World Clock and Sunrise/Sunset will display the time in 24 hour format if the 24 hour clock is selected here.

BT - Button tone. This setting is only relevant if you installed the buzzer connector, and it toggles the beep when changing modes. If Y, the buzzer will sound a tone when Mode is pressed. Change to N to make the Mode button silent.

TO - Timeout. Sets the time until screens that time out (like Settings and Time Set) snap back to the first screen. 60 seconds is a good default for the stock firmware, but if you choose a custom firmware with faces that you’d like to keep on screen for longer, you can set that here.

LE - Low Energy mode. Sets the time until the watch enters its low energy sleep mode. Options range from 1 hour to 7 days, or Never. The more often Sensor Watch goes to sleep, the longer its battery will last — but you will lose the seconds indicator while it is asleep. This setting allows you to make a tradeoff between the device’s responsiveness and its longevity.

LT - Light. This setting has three screens:

  • The first lets you choose how long the LED should stay lit when the Light button is pressed. Options are 1 second, 3 seconds and 5 seconds, or “No LED” to disable the LED entirely.
  • The second screen, titled “blu”, sets the intensity of the blue LED. Values range from 0 (off) to 15 (full intensity)
  • The third screen, “red”, sets the intensity of the red LED, again from 0 to 15. On the last two screens, the LED remains on so that you can see the effect of mixing the two LED colors. On the Special Edition boards, you’ll have red, blue and a variety of shades of pink and purple to experiment with!

Time Set

The Time Set watch face allows you to set the time on Sensor Watch. Use the Light button to advance through the field you are setting, and the Alarm button to change the value in that field. The fields are, in order: Hour, Minute, Second, Year, Month, Day and Time Zone.

For features like World Clock and Sunrise/Sunset to work correctly, you must set the time to your local time, and the time zone to your local time zone. This allows Sensor Watch to correctly offset the time. This also means that when daylight savings time starts or ends, you must update both the time and the time zone on this screen.