HARDWARE FEATURES
32-bit ARM Cortex-M4F Processor
BLE ULP Communication
1 Year Long Battery life
Heart rate, Pulse oximetry, Body Temperature & Fitness Tracking
Edge Analytics compliant (Cloud Integration)
Android and iOS Mobile App (optional)
40.1mm diameter x 14mm height (can be reduced with standard battery sizes)
USB Battery Charging Provision
FUNCTIONALITY
Health Checkup Band is a ultra-low power device which unlike fitness trackers, can also measure and report medical parameters besides general user fitness data. Equipped with the capability to measure heart-rate and pulse oximetry, the device can be used for remote patient monitoring with the use of an additional gateway device that is Wi-Fi enabled.
Below provided block diagram clearly indicates all the hardware peripherals included in the device which shall be explained in detail
Figure 1(a): Device Architecture Diagram
The hardware is powered by a high density non-rechargeable battery that can sustain operation for a year. If required, the battery can also be replaced with a rechargeable low-density battery with a few months of battery backup and then charged back via the provisioned USB port.
LOW POWER DESIGN
Optimized with minimal number of components and an ultra-low power NRF52832 processor from Nordic Semiconductor, the device communicates over BLE 5.0 with other Bluetooth enabled appliances attributing to its year-long battery life. The design was optimized to use minimum amount of power for operation with very few components which also is an indication of reduced manufacturing cost. The below provided schematic was inferred to design the first version of the hardware’s PCB.
Figure 2(a): Device Hardware Schematic
HARDWARE DESIGN
The hardware design was initially concluded to be similar to Fitness trackers by both design and form factor as they are quite general in the market and have been widely accepted across different market segments. Below is a snapshot of the PCB that was prototyped to demonstrate the minimum viable product.
Figure 3(a): MVP PCB Design
The assembled device is shown below for reference. It is to be noted that due to size constraints, a nominal low gain directional Trace Antenna was used.
Figure 3(b): Assembled MVP hardware
The device is JTAG programmable using any standard JTAG programmer with SWD interface. The below image shows the MVP hardware in operational condition after being programmed using a JTAG programmer. For testing purpose, the Board was powered up over the USB charging port interface.
Figure 3(c): MVP Hardware in Functional state
CORE BILL OF MATERIALS
Heart Rate Sensor – MAX30102
Pulse Oximeter - MAX30102
Body Temperature – MAX30205
Accelerometer & Gyroscope - LSM6DS3
Processor – NRF52832
Battery – Coin Cell CR2477
BLUETOOTH COMMUNICATION
The device transfers data over standard BLE Services and Characteristics. Since, the device transmits an array of heterogenous data that belongs to various domain, a common UART service was used to transmit the data over Tx Characteristic as JSON or CSV as these formats are quite flexible for encapsulating various analytical data as one object and has widely been used in computing and cloud environments for exchanging data. The below image shows the working MVP hardware transmitting measured data over BLE service and characteristic.
Figure 4(a): Data from MVP seen on NRF52 Connect Diagnostic Android App
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