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This will be my second attempt at building a smartwatch. I’ve built one version before, which resulted in the espWatchOS repository, and a working prototype. Take a look at the results below:

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The case is 3d printed with carbon fiber PLA and the wrist strap is printed with black TPU, which is slotted into the case at the top and bottom. It features

  • an ESP8285-M3 (i.e. the CPU, 160MHz, WiFi, ~50KB RAM, 1MB flash, a few GPIOs for I2C and SPI)
  • a 1.54” e-paper display (200x200px), panel is a GoodDisplay 1.54 200x200 on a breakout board from Heltec
  • a Bosch BME280 (i.e. the sensor, barometer, thermometer, hygrometer)
  • DS1307 Realtime Clock (desoldered from the RTC modules)
  • MCP1700 3.3V LDO
  • MCP73831 LiPo Charger
  • a 450mA LiPo
  • a PCB to hold everything together:
  • two buttons, a switch, and some resistors/capacitors according to the datasheets of the components above

This was a fun experience, and I learnt a lot. The reason I want to do this again, from scratch, is feedback from the community.

Many suggested to add bluetooth support, to synchronize with a smartphone or attach other devices like HR monitors. As I chose the ESP8285, there was no Bluetooth involved. Hence the next version will be based on the ESP32 (which has WiFi and Bluetooth, and more power ;)).

This does not mean I am going to write all the code necessary to sync with a phone, but it will be possible for others to add this :o).

The size. Many said that it’s too big/thick/square etc. And in fact they are right. I’m still proud AF about my achievement though :).

GPS. I really like my current outdoor watch. The battery lasts for ages, and it does GPS tracks. It’s kind of clunky (bigger than my approach above), and the GPS is sometimes dodgy, or simply wrong. The tracks can only be downloaded using a proprietary software and access via the cloud. To be frank, I understand the convenience of this, but I consider my location data as personal data that is none of anyones business. That is why I have the outrageous idea of adding a micro sd-card slot, to store GPS tracks. Pop out the card after vacation and use your favorite tool to view the track. Also, I want to add Open Street Map data, to be able to see where you are :). Offline. :P

Now, this is a bit of an idea, and maybe I will fail. But this time I will document everything first, then implement it. So you can follow me step by step and can build your own. Let’s see what happens

Step 1: the Idea

I stumbled across this display on aliexpress: 2.13” flexible e-ink 212x104px

The flexibility shown in the product video is source of the idea to move away from the square and clunky feeling. In marketing terms to give it a more organic design ;):

This looks promising, and I want to build something with it.
First, I drew this sketch how the smartwatch could look like.

In the meantime I have moved away from three separate buttons to a three-way switch (up, down, enter), and it will need less space on the PCB.

Step 2: Components

Currently, I’m thinking about using the following components:

Currently, I’m waiting for the parts to arrive, and continue with prototyping. The best way for you to stay up to date is to follow me on Instagram:

Step 3: Prototyping


If you are interested in sponsoring the development of this open source project, maybe in the form of

  • filament (PLA, TPU, …)
  • electronics (ESP, smd components, …)
  • PCBs
  • tools (soldering irons, 3d printers, …)

You will be listed on this page, as well as in the work in progress documentation on social media. Usually, I have most of the tools and materials already in my makerspace, but if you want to support others in joining this project (or in general), we can also arrange giveaways. ;)

Contact me via mail, or instagram (see footer of this page).