Chhavi is a tiny, wireless, touch-capacitive fingerprint sensor with high-end security capabilities, support for ultra-low-power operation, and optional NFC connectivity. Its open source firmware is fully compatible with Arduino IDE. Powered by ESP32 and equipped with an FPC BM-Lite fingerprint sensor, by Fingerprints, Chhavi gives you and your projects access to the superior biometric hardware found in many smartphones. Unlike optical fingerprint sensors, which are large and power hungry, this capacitive biometric sensor is tiny, accurate, and power efficient.
During our design process, we determined that NFC communication is a powerful feature for many of the same applications that might require a high-quality fingerprint sensor, yet we could not find a major ESP32-powered NFC controller. So we built one into Chhavi as an optional feature. We also added an optional battery to simplify installation and to facilitate mobile deployments. The result is a tiny device with a cutting-edge fingerprint reader, Wi-Fi and Bluetooth capability, and support for NFC and battery power if you need them.
Perfect for Physical Security, Device Authentication, Personnel Management, and More
Whether it’s drawing power from a battery or plugged in through USB, Chhavi is well suited to all kinds of fingerprint-sensor applications: signing in to a desktop computer, unlocking a password manager, implementing door locks and other physical security controls, powering attendance or personnel-management systems, or adding biometric authentication to a DIY hardware project – to name just a few examples.
Wireless, Battery-Powered, Biometric Locking Mechanisms
Personnel Management & Data Retrieval
Flexible, Easy to Use, and Full Featured
Chhavi comes with an open source library that makes it easy to program using Arduino IDE. And because it includes a built-in USB-to-UART adapter, you can program the ESP32 module right out of the box. Do you prefer working with Espressif’s ESP-IDF framework? Don’t worry, we’re developing a library for that as well!
Despite its tiny, 26 x 26 x 9 mm size, Chhavi is packed full of quality-of-life features as well. It includes a vibration motor, for example, that provides immediate haptic feedback in the event of a successful or unsuccessful fingerprint scan (or that you can re-purpose for other applications as needed). In addition to an MCU reset button, Chhavi also comes with an intuitive on/off switch that allows you to preserve power when it’s running off a battery. (And if you don’t need this feature—if it’s drawing power through USB, for example—you can use that interface as a GPIO instead.)
Add to the above a modular design, an IP7X sensor panel with remarkable physical durability, robust power-management circuitry, longevity estimated at 10 million scans, a built-in 3D antenna…and the list goes on.
Features & Specifications
Physical Features
- 26 x 26 x 9 mm (without battery)
- One MCU reset button
- One power-switch (user-configurable)
- Vibration motor for haptic feedback
Processing
- 32-bit 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 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 can power down MCU when battery power is low
- ESD protection on 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 ¹ & NFCIP-2 ²
- ISO/IEC 14443A, ISO/IEC 14443B PICC, and NFC Forum T4T modes via host interface ³
- 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 ⁴
- 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) ¹
- ISO/IEC 15693/ICODE VCD mode ⁵
- Supports card emulation as well as reader mode
¹ ISO/IEC 18092 (NFCIP-1) edition, 2013-03-15. This is similar to Ecma 340
² ISO/IEC 15693 part 2: 2nd edition (2006-12-15), part 3: 1st edition (2001-04-01)
³ ISO/IEC 14443 parts 2: 2001 COR 1 2007 (2007-11-01), part 3: 2001 COR 1 2006
(2006-09-01) and part 4: 2nd edition 2008 (2008-07-15)
⁴ NFC Forum Device Requirements V1.3
⁵ ISO/IEC 15693 part 2: 2nd edition (2006-12-15), part 3: 1st edition (2001-04-01)
Click to enlarge
Comparisons
| Chhavi | GT521F52 Optical Sensor | R301T Fingerprint Module | SeeedStudio Grove | |
|---|---|---|---|---|
| Capacitive Touch | Yes | No | No | Yes |
| Low Power | Yes | No | No | Yes |
| Wi-Fi | Yes | No | No | No |
| BLE | Yes | No | No | No |
| USB | Yes | No (UART) | No (UART) | No (UART) |
| NFC | Optional PN7150 | No | No | No |
| Battery Powered | Optional | No | No | No |
| Open-Source | Yes | No | No | No |
| Works With Arduino | Yes | Can be made to work | Can be made to work | Yes |
| Main Controller | ESP32 | None (needs host) | None (needs host) | None (needs host) |
| False-Acceptance Rate | 1/500000 | 1 / 10000 | 1 / 10000 | 1/20000 |
| Verification Time | 0.4 seconds | 1.5 seconds | 0.3 seconds | 0.34 seconds |
| Price | $49 | $40 - $50 | $20 - $25 | $30 - $35 |
Support & Documentation
Our open source files are available in our public GitHub repository, you can find more information about Chhavi’s biometric sensor on Fingerprint‘s website, and you can reach us by way of the Ask a technical question link below. (Please do!)
Manufacturing Plan
In order to ensure that we can respond quickly to any issues that might arise during the manufacturing process, we will begin Chhavi production in our lab, where we have everything we need to handle even a very large batch. (Once we have completed all crowdfunding orders and stock pre-orders, we will shift production to a contract manufacturer.) In order to deliver a quality product, we believe it is important to verify the functionality of the final design. To that end, we have already completed the development, prototyping, and testing of Chhavi, which means we are now ready to manufacture and ship any quantity of boards!
Fulfillment & Logistics
After testing and packaging the Chhavi production batch, we will send them on to Crowd Supply’s fulfillment partner, Mouser Electronics, who will distribute them to backers worldwide. You can learn more about Crowd Supply’s fulfillment service under Ordering, Paying, and Shipping in their guide.
Risks & Challenges
While Chhavi was designed with large-scale production in mind, the prototyping phase of this project was a crucial one, and it led to several insights that guided our subsequent development and testing efforts. It also gave us time to carry out an analysis of the project’s Strengths, Weaknesses, Opportunities, and Threats (SWOT). After a few rounds of prototyping, we now have access to a reliable supply chain and confidence in our ability to deliver on our commitments.
