KT148A Sound Chip Quick Application Alarm Box Greeting Card

Project Overview

Project Name: KT148A Voice Chip Integration

1. What is your project about?

The project involves integrating the KT148A voice chip into a custom hardware system to enable audio playback functionality. The KT148A is a 32-bit DSP voice chip in an SOP8 package, featuring:

• 420KB built-in storage (supports up to 420 seconds of audio).
• Direct 0.5W speaker drive (8Ω impedance).
• User-replaceable voice content via serial port.
• Low power consumption (25µA standby, 1.7µA shutdown).
• One-wire serial control for commands like playback, looping, and volume adjustment.

Applications:

• Interactive devices (e.g., toys, doorbells).
• Announcement systems (e.g., gaming machines, retail prompts)
• Low-power IoT devices requiring audio feedback.

2. Why did you decide to make it?

The KT148A was chosen for its:

• Cost-effectiveness: Lower cost compared to traditional OTP chips with reprogrammability.
• Ease of Use: No specialized tools needed; voice updates via PC serial port.
• Flexibility: Supports up to 224 voice segments and combination playback.
• Compact Design: SOP8 package fits space-constrained PCBs.

Key Motivations:

• Replace expensive/rigid OTP voice chips in existing products.
• Enable dynamic voice updates without hardware changes.
• Achieve low-power operation for battery-powered devices.

3. How does it work?

Hardware Setup

• Power Supply: 2.0V–5.2V (Pin 8: VBAT). For voltages <3.3V, short VBAT (Pin 8) and VDDIO (Pin 7).
• Speaker Connection: Non-polarized connection to SPK1 (Pin 5) and SPK2 (Pin 6).
• Control Interface:
• One-wire serial: Send commands via PB1 (Pin 3) with 1K series resistor.
• Test Trigger: Ground PB0 (Pin 4) to play next voice segment

Software Workflow

1.Voice File Preparation:

• Convert audio (e.g., WAV/MP3) to .F1A format using provided tools (16KHz/8KHz recommended).

2.Download to Chip:

• Short SPK1 (Pin 5) to ground during power-up to enter download mode.
• Use CH340G USB-to-TTL module (115200 baud) to transfer files via PC software.

3.Command Control:

• Play Voice 1: Send 0x01 (one-wire protocol).
• Loop Playback: Send 0x01 + 0xF2 (20ms delay between commands).
• Volume Adjust: Send 0xE0–0xEF (min to max).

Example Code (One-Wire Protocol)

void play_voice_segment(u8 segment) {  
  oneline_send_one_data(segment);  // e.g., 0x01 for Voice 1  
  udelay(20000);                   // 20ms delay  
}

Power Managemen

• Ultra-Low Power Mode: Send 0xF0 to reduce consumption to 1.7µA. Wake by pulling PB1 low for 40ms.

Challenges & Solutions

• Low Volume: Use larger speakers (e.g., 8Ω 1W) or external amplifiers (e.g., HAA8002D).
• Combination Playback Delay: Trim audio silences or reduce playback speed (Section 4.2).
• Download Failures: Ensure correct baud rate (115200) and stable power supply (add 10µF capacitor).

Conclusion

The KT148A provides a balance of affordability, flexibility, and low-power operation for embedded audio applications. Its one-wire control and offline voice updates make it ideal for prototyping and mass production. For advanced needs (e.g., DAC output), the KT142C-SOP16 is recommended.