Enhancing Barcode Scanner Design

Advantages of an Integrated Solution Based on a 32-bit Microcontroller

Barcode scanners have become such a ubiquitous technology that it is easy to take the complexity of their underlying designs for granted. Barcode scanners require multiple discrete integrated circuits and an array of passive and active circuitry to provide the functionality and reliability that end users have come to expect. Many barcode scanners generally use an optical sensor, such as a charge-coupled device (CCD), which outputs an analog representation of what is “visible” to the sensor to an analog-to-digital converter (ADC) controlled by a microcontroller (MCU). The MCU interprets the ADC’s output as a sequence of thick and thin black and white bars and processes this sequence further to derive a string of characters from the pattern. The character sequence may be encoded in any one of a number of well-defined barcode protocols, such as Code 39.Additional features found in barcode scanners include USB connectivity, regulators, audio output (usually driven by a discrete digital-to-analog converter (DAC) or simple pulse-width modulation (PWM)), and other glue logic for level-shifting between components running from 3 volts, such as the MCU, and components running from 5 volts, such as the CCD.

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