Chhavi

A wireless, open source, ESP32-based fingerprint sensor with optional NFC

Chhavi is a touch-capacitive, wireless, NFC-enabled fingerprint sensor with ultra low power and high end security capabilities. Chavvi’s open source firmware is fully compatible with Arduino IDE. Featuring Fingerprints’ FPC BM-Lite fingerprint sensor and the incomparable ESP32, Chhavi is simply superior fingerprint sensing hardware, just like the fingerprint sensor in your smartphone. Unlike optical-based fingerprint sensing, which is too large and power hungry, Fingerprints biometric sensor is highly accurate, tiny, and has low-power functionality. During our design process we decided that NFC is a key part of secure access and that there is no majorly available NFC + ESP32 enabled controllers, so we integrated all of this plus a remote capable battery into one tiny little device, Chhavi. A WiFi + BLE/BT + USB + Fingerprint sensing + NFC integrated + battery capable module.

Perfect for Locking Systems, PC Security, Personnel Management and More

Chhavi is useful in a number of fingerprint sensor applications, especially considering its wireless, remote low power and NFC capabilities. Chhavi is perfect for PC security, such as password managers or local authentications, as well as battery-based remote systems, a wide variety of locking systems and even attendance/personnel management systems, just to name a few.

Chhavi: Wireless, Battery-Powered Fingerprint Sensing Demo

Features & Specifications

  • ESP32 WiFi/BT controller (2.4 Ghz)
  • FPC BM-LITE Module (99% accurate fingerprint sensing)
  • 250-500 maH LiPo battery
  • deep sleep functionality due to capacitive fingerprint sensor.
  • PN7150 NFC controller
  • CP2102 USB - UART IC

Processing

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

Wireless

  • 2.4 GHz WiFi - 802.11 b/g/n
  • Bluetooth BLE 4.2
  • 3D antenna: Fractus
  • 13.56 MHz (NFC)

Power

  • 900 mA ,3.3 V LDO regulator
  • Optimized power path for low-power battery usage
  • LiPo battery management
  • Power (red) & charge (orange) LEDs

Connectivity

  • USB + serial/UART for programming (CP2102)
  • I2C interface with PN7150

NFC Specifications & RF Protocols

  • 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

Fingerprint Sensor

  • Protective sensor coating: scratch and ESD resistant
  • One-to-one verification mode
  • 0 Matching against 1 template
  • Finger detect functionality
  • 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 : 8.0 x 8.0 mm
Open Source Documentation & Resources

You can find our open source files in our public GitHub repo. You can also get more information about Fingerprint’s biometric sensor that we use on their website.