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Health PCB and Firmware Update

· 2 min read
Jakob Krantz
Jakob Krantz
Senior Software Engineer and ZSWatch Creator and Maintainer
Daniel Kampert
Daniel Kampert

It's now been two months since our last update and a new one is very much due!

We’ve hit two major milestones:

  • A prototype PCB for health tracking
  • Firmware updates over USB and BLE

Let’s dive into the details....

Health Tracking Prototype​

We’ve completed the design and assembly of a prototype board to validate the future health-tracking add-on PCB for ZSWatch. This board helps us test components, write drivers, and troubleshoot more easily before moving to a final compact version.

To simplify testing, we integrated an nRF54L15 BLE MCU, allowing the board to operate as a standalone unit.

The cool part? It can stream heart rate data live to the ZSWatch over Bluetooth! Below is a quick demo of heart rate data being plotted in real time. It's still very much a hacky prototype—but it works.

Check out the in-progress driver and app here:
https://github.com/ZSWatch/Zephyr-MAX32664C

Firmware Updates via BLE and USB​

We’ve added a bootloader, which means you can now update the ZSWatch firmware wirelessly via BLE—or through USB (in case ZSWatch firmware breaks and Bluetooth isn’t available.).

Even better: you can update directly from the Firmware Update page on zswatch.dev.
Firmware artifacts are pulled from GitHub Actions automatically, making updates simple.

We also added support for uploading the full filesystem image, which contains most UI assets.

Improvements for later:

  • Ideally, only real known working releases should show
  • Bundle firmware and filesystem into a single update process

You can also update the firmware using nRF Connect Device Manager or other tools listed in the Zephyr documentation.

Bonus (XIP)​

Another smaller, but very important update is that we after some fiddling around got XIP (Execute-in-Place) working on ZSWatch, allowing code to be run directly from the external flash. It was essential to fit the bootloader and USB support, and it opens up a lot more headroom for the firmware going forward.

Next up​

  • Evaluate the health tracking PCB’s performance
  • Design a casing for wearing the health tracking PCB in order

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