Joey Castillo Unveils Sensor Watch Pro, a Hackable, Low-Power, Open Source Wristwatch Platform

An update to the open-source and hackable Sensor Watch is coming soon. Joey Castillo from Oddly Specific Objects announced a Crowd Supply campaign for Sensor Watch Pro. This new addition to the watch line builds on the already hackable platform with options for expansion.

Sensor Watch Pro is a replacement PCB for Casio wristwatches that utilize "Module 593," such as the Casio F-91W. It prioritizes low power consumption by not incorporating features like Bluetooth, Wi-Fi, or a high-resolution screen. Despite the absence of power-hungry features, it contains a lot of hardware with hackable capability.

With this new introduction, there are three Sensor Watches: the original, Lite, and Pro. The original is no longer available because the Sensor Watch Lite replaced it. The Lite streamlined the original design by removing the 9-pin flex cable connector and moving the temperature sensor to the PCB.

All three variants use a low-power Microchip SAM L22 microcontroller. These chips have an Arm Cortex-M0+ core running up to 32 MHz with 256 KB on-chip flash and 32 KB of RAM. The RAM retains its contents while in low-power modes. The Sensor Watch board also includes an external 8 KB flash chip. The L22 contains many peripherals that make it ideal for Sensor Watch. For example, it has a built-in RTC (driven by an external 32.768 kHz crystal) and a hardware driver compatible with the Casio LCD!

Building on the success of Sensor Watch Lite, Sensor Watch Pro adds new hardware features. It includes an infrared sensor for light detection or receiving data, upgrades the LED to RGB, and reintroduces the original's 9-pin flex cable PCB connector for sensor add-on boards.

With Pro bringing back the original's nine-pin sensor connector, Sensor Watch Pro will offer an accelerometer (LIS2DW) add-on for motion tracking (streaming to USB or UART), tap detection, and fall detection. Alternatively, hardware hacking-inclined users can design a custom add-on flex circuit using the nine-pin connector to incorporate any sensor they prefer, showcasing the watch's versatility.

The Sensor Watch community has demonstrated remarkable creativity in pushing the capabilities of the original always-on Casio LCD. These innovative uses display a wide variety of helpful information despite its limitations! An exciting mention in the campaign listing is a custom 11-digit segmented LCD option, further expanding the possibilities for creative display use.

Castillo teased the difference between the original and the new custom LCD in this Mastodon post. This example shows the additional information available when displaying (contrived?) data like a location.

One key reason for Sensor Watch's popularity is its exceptional battery life. The first battery test, conducted on the original hardware and firmware, lasted 425 days. In contrast, the more recent test on Sensor Watch Lite, running on optimized firmware, operated for 2.4 years—more than twice as long as the previous test.

The Sensor Watch Pro LCD has a built-in USB-Micro compatible footprint. You can plug it into a cable to connect to a PC. From there, it appears as a mass storage device or a reset button can put it into a U2F-compatible bootloader mode. There are two existing firmware options. Movement (and soon Movement 2.0) is a pre-built application to manage the screens or watch faces. This firmware is a great starting point if you just want to customize a display. Alternatively, the Sensor Watch library (compatible across all variants) gives bare metal access to the hardware.

Oddly Specific Objects has started a pre-launch on Crowd Supply. You can sign up on the Sensor Watch Pro product page to receive notifications when the pre-sale campaign goes live.

Update 2024-09-25: pre-orders are now live and available starting at $75 before shipping. Here is an update post with the annoucement.