Case Study | Application of KT142C Voice Chip in Smart Crosswalk Auditory Guidance System

I. Application Background

With the development of urban intelligent transportation, accessibility facilities are receiving increasing attention. For visually impaired individuals, relying solely on visual traffic signals is insufficient for safe street crossing. To address this, we have developed acrosswalk auditory guidance system for traffic light intersectionsbased on theKT142C voice chip, which uses audible cues to guide visually impaired pedestrians safely across streets.

II. Solution Overview

The system is installed on traffic light poles and operates in sync with pedestrian signals:

• 🔹 During green light: Plays rhythmic prompts to guide crossing.

• 🔹 During red light: Plays a different rhythmic pattern to indicate waiting.

• 🔹 Light-sensitive smart adjustment: Automatically switches between "daytime" and "nighttime" modes based on ambient brightness to avoid noise disturbance at night.

• 🔹 Volume and modes can be flexibly configured via serial commands or configuration files to adapt to different intersection requirements.

III. Advantages of KT142C in This Solution

1.Built-in storage, no external Flash required

The chip features320KB of built-in storage, capable of storing multiple audio prompts directly without requiring external SPI Flash, resulting in simpler hardware design.

2.Supports direct audio updates via USB

When connected to a PC via USB, the chip appears as a virtual USB drive, allowing prompt audio updates at any time without dedicated programming tools, making maintenance convenient.

3.Flexible playback control

• 🔹 Supports serial command control (e.g., playing specific audio, adjusting volume, looping playback).

• 🔹 Supports IO trigger playback, enabling direct interfacing with traffic light control boards.

• 🔹 Supports combined playback for seamless transitions between multiple audio segments.

4.Low-power design

The chip supports low-power mode (as low as 2µA), suitable for intersection devices operating continuously year-round. It can also be controlled via light sensors for on/off management.

5.Selectable audio output modes

• 🔹 PWM direct drive for speakers (0.5W/8Ω).

• 🔹 DAC output for external amplifiers (e.g., HAA2018), suitable for higher-power scenarios.

IV. Technical Implementation Details

✅ Audio File Planning

• 🔹 001.mp3 : Green light prompt tone (frequency 300–500Hz, 160ms on, 500ms off).

• 🔹 002.mp3 : Red light prompt tone (frequency 300–500Hz, 200ms on, 300ms off).

• 🔹 003.mp3 : Green light final 3-second prompt tone (accelerated rhythm).

• 🔹 Configuration file  config.txt  sets trigger modes, volume, output mode, etc.

✅ Brightness Sensing Control

An external light sensor detects ambient brightness, processed by an MCU:

• 🔹 Brightness > 200 LUX for 60 seconds → Daytime mode (volume ≤ 65 dB).

• 🔹 Brightness < 200 LUX for 60 seconds → Nighttime mode (volume ≤ 45 dB).

• 🔹 Nighttime mode persists for 180 minutes → Mute mode activated.

✅ Integration with Traffic Light Control System

• 🔹 IO level triggers playback of corresponding prompt tones.

• 🔹 Serial commands can also receive traffic light status instructions for more complex auditory guidance logic.

V. Measured Parameter Table

VI. Testing and Validation

We used:

• 🔹 Digital oscilloscope → to detect output waveform and frequency.

• 🔹 Spectrum analyzer → to analyze audio frequency range.

• 🔹 Sound level meter → to measure actual sound pressure levels.

• 🔹 Serial debug assistant → to verify command responses.

Test results show that the KT142C performs stably under continuous operation, temperature variations, and voltage fluctuations, meeting the long-term operational requirements of crosswalk guidance devices.

VII. Customer Benefits

• 🔹 Easy Integration: Simple peripheral circuitry—only two capacitors required for operation.

• 🔹 Convenient Maintenance: USB-based audio updates, no device disassembly needed.

• 🔹 Smart Control: Supports light-sensing and timing control for balanced guidance and environmental protection.

• 🔹 High Reliability: Industrial temperature range suitable for harsh outdoor environments.

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VIII. Technical Support and Resources

For more detailed design materials, schematics, configuration file examples, and other resources related to the KT142C in this application, visit our official resource repository.