You may have thought you could only metaphorically give your heart to someone, but with Enso, you can come pretty close to giving the real thing! Enso is an innovation lab that believes in sharing love first and foremost. Their vision was to bring your heartbeat to life and forge a deeper connection with yourself and your loved ones worldwide.
Once Enso’s founder described her project to us, we were fascinated. Up until then, we hadn’t worked on a project that delivered such a high level of user sensory feedback. Excited to be a part of the team, we agreed to take it on.
First, we held several meetings with the team to understand all the key players, desired product features, and mechanical design constraints. We understood Enso’s two highest priorities were to have a hardware design optimized for mass production with a low BOM cost, and a firmware design that offered a premium user experience.
We knew right away that component selection was key in the board design. This project occurred at a time when fully integrated system on a chip (SOC) Bluetooth solutions were not powerful enough to provide the experience we wanted. So, we set out to find a cost-effective chipset solution with as little supply management as possible.
The combination of our knowledge of the current IC supply along with our vendor relationships, enabled us to quickly find a low-cost MCU IC, a Bluetooth IC, and a biometric sensor module all from the same vendor. This solution provided top quality vendor technical support!
With the component list finalized, the project’s hardware contractor got to work on the schematics and layout while we began the firmware development.
During hardware design we often use a waterfall approach, but with firmware, we prefer an iterative, agile, approach. By using FreeRTOS in combination with a vendor-provided closed-source library for Photoplethysmography (PPG) signal processing, we quickly enabled our system to know the users' heart rates.
Next, we held a series of meetings with the client, to understand their requirements for the two main user features, a LED light animation to visually show the user’s heartbeat and the haptic feedback of the stone. These features were key in delivering the premium product Enso was looking for. We wanted to ensure the users would feel a realistic heartbeat from the stone that harmonized with the soothing LED animation.
One issue we encountered during our firmware development was how we were going to implement over-the-air (OTA) firmware updates. Most electrical devices today have one MCU with built-in support for the bootloader, the small piece of code that manages the update. But we had physically separate main MCU and BLE chips. There was no vendor support for this configuration. In order to ensure future firmware updates could be made via an app, by relying on our deep expertise in computer architecture, we built a custom bootloader with integrity checks to upgrade both chips simultaneously.
Another challenge we had to overcome in this project was when the first form factor boards arrived and we saw that an I2C address conflict was designed into the boards. With this type of issue, anyone’s gut instinct would be to scrap design and do another board spin. Knowing a new board would set back the project in both schedule and budget, we had to get creative in finding a work around. We ended up programming the firmware to configure the pins dynamically based on what device the MCU needed to access at a specific time. It worked! This enabled us to get back on schedule and continue the project without having to complete a new design
All our efforts were put to the test in a key project milestone, a user demo of our first prototype. The demo was a hit! In fact, our software design led the stone’s sensory feedback to feel so realistic, it gave birth to a new idea for the product. Enso asked,
Excited for a new challenge, we incorporated this request in our next firmware revision and ensured that the user could record data via the app and the app would store their data in the cloud and pull it upon request.
After our demo our last two tasks were to optimize the firmware for the maximum battery life and mass production of the final product. At Intercreate we ensure our designs undergo proper DFM and the manufacturing partner has everything they need for smooth production, including test fixtures for the electrical hardware.
This project was especially rewarding to us because we were able to truly see how our contributions helped the end customers and their families.
Principal Engineer: Dave Desrochers
Services: Firmware engineering, Hardware engineering, Prototyping, Test Fixture Development and, Mass Production Support
