Tuesday, January 19, 2010


Hey!!guys this post is for those who are interested to control speakjet.
Speakjet is sound synthesizing chip.

its features:
· Programmable, 5 channel synthesizer.
· Natural phonetic speech synthesis.
· DTMF and other sound effects.
· Programmable control of pitch, rate, bend and volume.
· Programmable power – up or reset announcements.
· Multiple modes of operation.
· Simple interface to microcontrollers.
· Simple “Stand Alone” operation.
· Three programmable digital outputs.
· Internal 64 Byte input buffer.
· Internal programmable EEPROM.
· Extremely low power consumption.
· Low pin count.
· Multiple case styles available.

In the beginning you don't have to know much about how it synthesizes music internally.
It can be controlled easily using serial interface.
NOTE:speakjet works on TTL logic and not RS232.So to control it through PC you need to have a level converter ic like max232.
It generates sound using basic unit of speech called allophones.A combination of desired such allophones will generate required sound.The SpeakJet is preconfigured with 72 speech elements (allophones),43 sound effects, and 12 DTMF Touch Tones.For more information read usermanual


Here u will come across diff methods to control Speakjet.But frankly speaking u will not be interested in events control .In this post we will learn how to control it using serial interface.You can interface speakjet with any microcontroller which is UART compatible.
Before starting working with it we have to set up the circuitary for the ic.


In demo mode the pins M0,M1,Rst are held at logic 1. i.e they are connected to vcc(2-5V).
In this mode the ic plays all the allophones and special sounds inside.And all pins on LHS are grounded.

For speakers we used a headphone and connected one of its pin to GND and other to Vout of IC.


In normal mode we connect M0 to gnd and M1 ,Rst to Vcc.
For normal mode we will need an amplifier (to hear o/p clearly).I used a commonly available
LM386 low power audio amplifier.

BYPASS capacitor -0.1 uF.

speakjet has a factory assembled baud rate of 9600.but you can change it as and when you wish.There is a simple routine to set baud rate.we will follow this routine every time we connect speakjet to microcontroller.

The code for atmega16 microcontroller

Wish you good luck for the speakjet project .