Use TI's low power c5x DSP for fingerprint identification block diagram and solution side

Design Notes
Fingerprint identification is used in a variety of applications, including electronic access control systems, smart cards, vehicle ignition switch controls, USB memory sticks with fingerprint-controlled access, and many other applications. The digital signal processing elements in fingerprint scanner can perform complex DSP functions such as filtering, transformation, feature extraction, matching operation and other algorithms.
Fingerprint sensors can use capacitive, optical, pressure, or thermal sensing techniques to capture the image of a finger feature. The most commonly used fingerprint sensor solution first illuminates the fingerprint using a laser or LED light, and then uses a CCD or a cheaper CMOS sensor for image acquisition. Fingerprint sensors are typically self-contained modules, including A/D converters that convert analog information to digitized data streams. Resolution, dynamic range, and pixel density are all factors that determine image quality and affect sensor accuracy.

Once the image is captured, the digital information is transmitted to the digital signal processor to generate a match. The first step in the matching process is to adjust the scanned fingerprint. Fingerprint readers rarely use complete fingerprints for identification. Instead, the DSP uses algorithms to extract the features and styles of each fingerprint to generate a unique digital code. The second step in the software flow is to read the code generated from the scanned image and compare it to a potential match for the database. The comparison step will require the system to access the fingerprint information in the networked database or nonvolatile memory.

The need for real-time signal processing in biometric fingerprint scanning makes the c55x DSP a noticeable solution for this application. The low power capability of the c55x in active and passive mode makes it a perfect match for fingerprint scanning applications, as the processor is in low-power mode for most of the time. The peripheral integration of the c55x DSP includes an on-chip LDO, on-chip memory, and a USB Phy for connection. Installing on-chip peripherals reduces total system cost by simplifying board layout and reducing the total number of chips. When the communication peripherals are installed on the same chip as the processor, it is also important to protect your device from the source of the ESD. All IO or communication peripherals or other sources of ESD that can be in contact with the human body should be protected. Devices like tpd3e001 can provide up to 15kV of multi-channel ESD protection for USB 2.0 interfaces.

The LCD Bridge found on the c55x can be used to display messages or options menus. The integration of the TSC2003 Touch screen controller with the application provides a way for the user to select Options from the displayed menu. The app also has audio capabilities built in to provide feedback to users in both the form of alerts and pre-recorded voice commands. This can be achieved by c55x's I2S function, which provides a digital audio stream for the audio DAC. The DAC3120 devices include a built-in class AB amplifier capable of driving 2.5-watt mono speakers, which converts digital audio streams into analog signals and improves system integration capabilities.

Use TI's low power c5x DSP for fingerprint identification block diagram and solution side