Chhavi – Ultra-Low-Power Fingerprint Sensor Featuring ESP32 SoC

Recent time has shown an increase in the number of fingerprint sensors and modules available in the Tech ecosystem following the need for physical security and biometric authentication for device and personnel management. One of the most recent is the new device by a hardware design company based in India – Chhavi.

Chhavi by Vicharak is a dense, wireless, touch-capacitive sensor built on ESP32 MCU with Wi-Fi and Bluetooth capabilities as well as an optional NFC features. It is based on open source code compatible with Arduino and has an FPC BM-Lite fingerprint sensor from Fingerprint which provides enhanced biometric performance in terms of accuracy and low power demand compared to optical fingerprint sensors.

Chhavi is built to meet ultra-low-power applications and high-end security requirements. The NFC feature of Chhavi is provided to solve the problem of high-quality fingerprint sensor requirements of most authentication and locking systems. There’s also an optional battery to support battery-based and mobile systems although it can be powered through a USB port.

The fingerprint sensor is further equipped with a vibration motor that can provide haptic feedback in applications such as notification of successful or unsuccessful user interface – scan. There’s also a self-generating or programmable ON/OFF switch that allows users to monitor and preserve power when the board is draining off a battery. This programmable switch can also function as a GPIO interface when the device is USB powered.

Features and Specifications Include:

Physical Features:

• 26 x 26 x 9 mm (without battery)
• 1x MCU reset button
• 1x power-switch (user-configurable)
• Vibration motor for haptic feedback

Processing:

• 32-bit ESP32 dual-core processor operating at 240 MHz
• 4 MB SPI flash

Connectivity:

• CP2102 USB-to-UART converter for serial programming
• I²C interface via PN7150

Power Management:

• 600 mA, 3.3 V LDO regulator
• LiPo battery management
• Support for 250 – 500 MAh LiPo batteries
• Capacitive finger-detection that allows for deep sleep when not in use
• Optimized power path for low-power battery usage
• Battery voltage-level detection
• Power (red) & charge (orange) LEDs
• Supply-voltage supervisor that can power down MCU when battery power is low
• ESD protection on the USB data bus
• Over-voltage protection (OVP) for USB power
• Over-current protection (OCP) for USB power

Fingerprint Sensor:

• FPC BM-LITE Module (99% accurate fingerprint sensing)
• Automatic finger detection
• Protective sensor coating is resistant to scratches and electrostatic discharge (ESD)
• One-to-one verification mode
• Front side IP rating: IPX7
• Durability: 10 million finger placements
• Scratch resistance (pencil hardness): 4H
• Sensor matrix: 160 x 160 pixels
• Number of pixels: 25,600 pixels
• Active sensing area: 8 x 8 mm

Wireless:

• 2.4 GHz 802.11 b/g/n Wi-Fi via ESP32
• Bluetooth BLE 4.2 via ESP32
• (Optional) 13.56 MHz NFC
• 3D antenna

NFC Specifications & RF Protocols:

• PN7150 NFC controller
• NFCIP-1  & NFCIP-2
• ISO/IEC 14443A, ISO/IEC 14443B PICC, and NFC Forum T4T modes via host interface
• NFC Forum T3T via host interface
• ISO/IEC 14443A, ISO/IEC 14443B PCD designed according to NFC Forum digital protocol T4T platform and ISO-DEP
• FeliCa PCD mode
• MIFARE Classic PCD encryption mechanism (MIFARE Classic 1K/4K)
• NFC Forum tag 1 to 5 (MIFARE Ultralight, Jewel, Open FeliCa tag, MIFARE DESFire)
• ISO/IEC 15693/ICODE VCD mode
• Supports card emulation as well as reader mode

Chhavi’s software support allows flexibility, easy and out-of-the-box programming for makers and DIY users with the help of its inbuilt USB-to-UART adapter. And according to Vicharak, the development of a library for ESP-IDF framework users is also on the way. Vicharak also points to Github for Chhavi’s source files and fingerprint’s website for biometric sensor information.

As of the time of this writing, Chhavi is only available for crowdfunding on CrowdSupply at $49 (for only fingerprint sensor); $59 (for the fingerprint sensor and NFC); $59 (for the fingerprint sensor and battery), and, $69 (for the fingerprint sensor, NFC and battery). An additional $8 (US) or $18 (Worldwide) shipping fee applies to all four rewards.

The funding campaign is scheduled to end on Nov 18, 2021, at 03:59 pm PST (11:59 pm UTC) for manufacturing to commence immediately. To join the funding campaign, and get more information on Vicharak’s Chhavi, visit CrowdSupply.

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