KT142C Chip – BUSY Pin Idle Voltage Only 0.2V? + Low Power Mode Configuration Guide

#programming #voicechip #embeddedsystems #development

📘 Overview

This document focuses on the BUSY pin behavior of the KT142C voice playback chip. The BUSY pin corresponds to pin 15 (PA12). During playback, it outputs low level (0 V); when idle, it should output 3.3 V.

However, after 5 seconds of inactivity, the chip automatically enters a 2 μA ultra-low-power mode — in this state, the BUSY pin becomes high-impedance. Consequently, the measured voltage drops to around 0.2 V, which is expected and not a fault.

⚡ Key Behavior Explanation

Normal Operation: BUSY pin outputs 3.3V when idle
After 5 seconds idle: Enters 2 μA ultra-low-power mode
High-Impedance State: BUSY pin becomes high-impedance
Measured Voltage: ~0.2V (completely normal)

🔧 Practical Solutions

External Amplifier Connection

When connecting to an external power amplifier, you should add a pull-up resistor to ensure stable logic levels:

Recommended values: 10 KΩ or 22 KΩ

Configuration via config.txt

You can customize the chip configuration by modifying the config.txt file when connecting the chip to a PC. Adjustable parameters include:

Trigger method
Playback volume
BUSY pin polarity
Low-power mode enable/disable (controlled by the 6th parameter in the configuration file)

🧩 Key Technical Notes

BUSY pin = PA12 = Pin 15
Playback state: Outputs low level (0V)
Idle state: Should output 3.3V (before low-power mode)
Low-power mode: Activated after 5 seconds of inactivity

✅ Summary

The KT142C's BUSY pin voltage of about 0.2 V when idle is normal, not a malfunction. This behavior results from the chip entering 2 μA ultra-low-power mode after 5 seconds of inactivity, during which the BUSY pin is high-impedance. To ensure compatibility with external circuits, add a pull-up resistor, or disable low-power mode through configuration.