Our customer Bloom approached us with the question to design for them a portable medical proof of concept device. The device has to be battery-powered, wearable, it has to interface to various sensors and it has to communicate over both USB and Bluetooth low energy. The device is designed as a first prototype for their clinical-grade wearable device to help expecting mothers track contractions without having to go to the hospital.
The devices communicates over USB to a computer, over Bluetooth low energy to mobile devices, and it can perform long-term data storage on an on-board SD-card.
The hardware prototype communicates to 6 accelerometers that can concurrently be read-out and processed. There are also 6 parallel channels for monitoring muscular activity through medical-grade stick-on pads. All sensors are connected to a low-power Actel FPGA to enable parallel processing of the sensor outputs. The FPGA output is communicated to an EFM32 Cortex M4 processor over the external bus interface of the processor.
We also designed fingernail-sized sensor PCBs with the accelerometers and a matching housing.
An on-board Lithium-Polymer charge circuit takes care of charging the built-in battery over the USB interface.
Key technologies we used to realize this system are:
- ultra low-power EFM32 Cortex M4 Wonder Gecko
- low-power MicroSemi Igloo FPGA
- state-of-the-art accelerometers
- medical-grade ADS1294 frontend for muscular activity detection
- BlueGigi BLE113 Bluetooth module