Project Background

What if diagnostic testing could become more accessible, repeatable, and easier to use outside traditional clinical settings?

This was the idea behind a connected diagnostic device developed by a UK-based medical startup for saliva sample analysis. Initially designed for COVID-19 detection, the device was created as a flexible platform with the potential to support other diagnostic applications, including pregnancy testing, infection detection, and broader point-of-care testing use cases.

The device was developed as an alternative to existing lateral flow tests, with the goal of improving diagnostic precision while reducing testing costs for families, office teams, and other groups that require accessible and repeatable testing.

The science behind the device is based on the measurement and analysis of electrochemical signals from saliva samples. After the sample is processed, test results are displayed on a mobile phone within 20 to 40 minutes via a Bluetooth Low Energy connection. The results are then transferred and stored in the cloud.

The Challenge

The main engineering challenge was translating a sensitive electrochemical measurement concept into a compact, battery-powered device.

This required close coordination between:

• analog frontend
• embedded software
• signal analysis algorithms
• BLE communication
• memory
• charging circuitry
• overall device behavior, and mechanical design.

The system had to support accurate signal acquisition and processing while also maintaining stable wireless communication and predictable operation during the full testing workflow.

At the same time, the project was developed during the global chip shortage, so the client wanted to reduce supply chain risk by keeping more than one hardware option available. In parallel with our development on a Nordic-based platform, another team was working on an alternative ST-based design.

This meant the firmware architecture could not be tightly coupled to one specific hardware implementation. It had to be structured in a way that would allow it to be ported across both platforms without requiring a complete firmware redesign.

Another important requirement was platform flexibility. Since the device concept was not limited to a single diagnostic use case, the hardware and firmware foundation had to support future adaptation without requiring a complete redesign.

Our Contribution

We supported the client across electronics design, firmware development, RTOS integration, algorithm implementation, testing, and prototype verification, design updates, EMC testing, and transfer to production.

Electronics design for a compact diagnostic device

The hardware design included key building blocks required for a connected diagnostic device:

• a Bluetooth Low Energy SoC with an ARM Cortex-M4 core
• an analog frontend chip for electrochemical signal measurement
• USB-C, flash memory, and Li-Po battery charging.

The electronics were designed to support signal acquisition, embedded processing, wireless communication, local storage, and battery-powered operation within one compact device platform.

Firmware development and RTOS integration

On the firmware side, the device firmware was implemented using Zephyr RTOS, providing a structured foundation for device operation, communication, timing, and further software development. To support the client’s strategy of maintaining both Nordic-based and ST-based hardware options, we developed firmware with portability in mind. This enabled the same core firmware architecture to be reused across both platforms, reducing development effort and minimizing dependency on a single hardware vendor.

It was developed to support electrochemical signal measurement and analysis, enabling the device to process sample data and prepare test results for display through the connected mobile phone.

Prototype verification and functional testing

We also performed design and prototype verification. Functional testing was carried out to validate key device operations, including signal-related workflows, embedded software behavior, BLE communication, and general device functionality.

EMC pre-compliance testing

To reduce the risk of late-stage compliance issues, we performed EMC pre-compliance testing to identify potential electromagnetic compatibility risks early and give the client a clearer path toward further product validation.

Results

As a result, the client received a verified prototype platform for a connected diagnostic device that combines saliva sample analysis, electrochemical signal processing, and BLE-based result communication.

The project delivered:

• electronics design for a compact connected diagnostic device
• firmware development based on Zephyr RTOS
• a portable firmware foundation designed to support both Nordic-based and ST-based hardware platforms
• integration of BLE connectivity, analog signal acquisition, USB-C, flash memory, and Li-Po battery charging
• algorithm implementation for electrochemical signal analysis
• prototype verification and functional testing
• EMC pre-compliance testing to reduce certification-related risk
• a technical foundation adaptable to future diagnostic applications beyond the initial COVID-19 use case

The developed device achieved 10% higher precision than existing lateral flow tests, while supporting lower testing costs for families, office teams, and other groups that require accessible and repeatable testing.