Voice Chip Technology: Enabling Appliances to "Speak" - Selection Guide and Development Examples

Three Main Voice Solution Comparisons

1. OTP Voice Chips (One-Time Programmable)

Characteristics:

• Single programming opportunity with permanent data retention

• Lowest BOM cost

• Direct speaker drive capability

Typical Circuit Diagram:


Driver Code:

sda = 0;
wait(300); /* >2ms initialization */
for (i = 0; i < 8; i++) {
    sda = 1;
    if (addr & 1) {
        wait(15); /* 2400us high */
        sda = 0;
        wait(5);  /* 800us low */
    } else {
        wait(5);  /* 800us high */
        sda = 0;
        wait(15); /* 2400us low */
    }
    addr >>= 1; /* Shift address right */
}
sda = 1;

2. KT148A Reprogrammable Voice IC

Advantages:

• SOP8 package with UART interface

• User-updatable voice content

• Built-in PWM speaker driver

Reference Circuit: 

Control Example:

void send_data(u8 dat) {
    IO1_LOW();            /* Start condition */
    udelay(5000);         /* 6ms delay */
    for(i=0; i<8; i++){
        if(dat & 0x01){   /* Send '1' */
            IO1_HIGH(); udelay(500); /* 600us */
            IO1_LOW(); udelay(170);  /* 200us */
        } else {          /* Send '0' */
            IO1_HIGH(); udelay(170); /* 200us */
            IO1_LOW(); udelay(500);  /* 600us */
        }
        dat >>= 1;        /* Shift transmission */
    }
    IO1_HIGH();           /* Release bus */
}

3. TTS Synthesis Chips

Key Features:

• Dynamic text-to-speech conversion

• No pre-recording required

• Multi-language support

Implementation:

line = io.read("*l")          -- Read text line
audio.tts(0, line:trim())     -- Play content
while true do
    msg = sysplus.waitMsg()   -- Wait for playback complete
    if msg[1] == "MSG_PD" then break end
end

Selection Recommendations

Key Takeaways:

1. OTP delivers the lowest cost for fixed content

2. KT-series offers the best balance of flexibility and value

3. TTS enables completely dynamic content generation

Complete project files available upon request. Let's connect to discuss your specific voice implementation challenges!

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