September 25, 2019 by Sam Holland
The AS7026GG Evaluation Kit is created to evaluate all functions of the AS7026GG vital signs biosensor and to test the technology in several applications.
The break-out board contains the temperature sensor (AS6200), accelerometer (LIS2DH12), biosensor (AS7026GG), and electrodes to ensure full flexibility. The board can be reconnected to the mainboard using flexible printed circuit cable and can be used in any application.
The AS7026GG is connected to the user’s PC with a USB connection and comes with a GUI that gives the user the freedom to change AS702x register settings. The kit also comes with a software development kit that contains blood pressure (BP), HRV (heart rate variability), and HRM (heart rate monitor) friendly algorithms for consumer health applications.
The AS7026 operates on electrocardiogram (ECG) and photoplethysmography (PPG). It has algorithms for converting ECG and PPG readings into digital HRV, HRM, and continuous blood pressure values.
The BP measurement fulfills the IEEE Std 1708-2014
In addition to HRV/HRM and BP, the module also enables skin resistivity and skin temperature measurements by having interfaces that connect to external sensors
An IEC 60601-compliant DC/DC converter helps prevent a direct connection from the electrodes to the power grid. This prevents physical contact between the power grid and the board’s break-out part
The AS702x evaluation software consists of client software (namely GUI) and firmware. The firmware implements a virtual COM port CDC (Communication port and Communication Device Class) interface for client communication and critical sign detection applications. It runs on an Arm Cortex M4 microcontroller. The client software displays algorithm data, board data, and raw data. For further analysis, raw data can be logged and exported as .csv.
Moreover, the below bullet-points outline what the biosensor itself has to offer:
Synchronised ECG and PPG acquisition that facilitates BP measurements
An analogue electrical front end for extra information to the user
A hardware sequencer that offloads processor tasks and allows for a longer operation time
Improved optical path, which accommodates all skin types
An embedded ambient light rejection system
A low-noise analogue optical front end that guarantees clear HRM measurement quality
A single-device integrated optical solution that allows for the smallest application sizeLow noise analogue front end for ECG applications with dry electrodes
The photocurrent and voltage sensor has the capability of taking ECG, PPG, proximity, and skin resistivity/temperature measurements. It integrates an electrical analogue front end, an ECG amplifier, a light to frequency converter, and an optical front end; plus, it features a 14-bit successive approximation ADC, 4 general purpose input/output pins, a built-in sampling sequencer, an I²C interface and a 128-byte first in, first out (aka FIFO) memory.
The AS7026GG evaluation kit is compatible with wearable applications. Pictured: a close-up of 4 fitness bands. Image credit: Flickr.
The optical front end is made up of:
4 individually-configurable LEDs that can either be controlled manually or via the built-in sampling sequencer
Trans-impedance amplifier (TIA)
2 identical signal conditioning blocks
TIA output filter
6 photodiodes for converting light into electrical current
Alongside its compatibility with smartphone, automotive, heart rate monitoring, cuff-less BP measurements, and optical sensor platforms, the AS7026’s small form factor and the low-power design make it suitable for applications in smartwatches, smart patches, fitness bands, and sports watches. All in all, applications where board space is limited and where users prefer extended, multi-day intervals between battery recharges.
