Nuts & Volts - March 2006

wire wrapping power, ground, and speaker wires to the PCB. I set my DC power supply to eight volts (there is an on-board 7805 regulator on the PCB to make + 5 volts) and connected the power lead. The speaker instantly said “Ready.” Wow! What a nice indication that the PCB is working. This, by the way, was the first thing the SpeakJet said to me.

■ FIGURE 2. Here is the setup on my workbench that interfaces the Z8 Encore! XP development board to the SpeakJet and TTS256. The SpeakJet supercarrier PCB is at the top to the right of the speaker. The T TS256 is plugged into the large protoboard.

3. Next, I installed the PhraseAlator application, which allows you to control the SpeakJet via a serial connection. Figure 1 shows the application window. Clicking on a sound icon — such as any of the Robot sounds R0 through R9 — instantly plays the sound sample (allophone) on the SpeakJet. All allophones required to synthesize human speech are available in the PhraseAlator, plus many other useful sounds, such as the Touch Tone and Musical sounds. The PhraseAlator controls the SpeakJet via a serial cable from the PC’s COM port, operating at 2400 baud. The PhraseAlator requires the registered file MSCOMM32.OCX to operate. Simply place a copy of the file in the \windows\system folder and then run the REGSVR32 application to register the file, as in:

baud. Figure 2 shows the results of my breadboarding.

The TTS256 (like the SpeakJet) requires a TTL serial waveform (eight data bits, no parity, one stop bit, abbreviated as 8N1). An IC on the SpeakJet supercarrier PCB (the eight-pin DS275) converts from RS232 levels to TTL.

By carefully tapping into signals available on the PCB, and by setting the jumpers appropriately, I was able to use the DS275 to drive the TTL signals on the TTS256. The TTS256, in turn, controls the SpeakJet with its own TTL serial connection, as illustrated in Figure 3.

regsvr32 \windows\system\mscomm 32.ocx

The PhraseAlator, SpeakJet manual, and MSCOMM32.OCX are all available via download.

4. After playing with the PhraseAlator for several minutes, listening to all the different sounds (these sounds are the second ‘thing’ the SpeakJet said to me), I then interfaced the SpeakJet PCB with the 28-pin TTS256 Text-To-Speech translator designed specifically for the SpeakJet. You just send an ASCII text string to the TTS256, such as “Hello, please talk,” and the TTS256 does all the work of controlling the SpeakJet to make the required words come alive.

The ASCII text string is sent to the TTS256 in serial form also, at a speed of 9600

5. Before connecting the Z8 Encore! XP as the host controller, I used my PC and ran Hyper Terminal to communicate with the TTS256. I configured HyperTerminal for 9600 baud and 8N1, established a connection, typed in the phrase “Hello, please talk,” and pressed Enter. The words “Hello please talk” played out on the speaker. I was so pleased, I entered a second phrase and heard “This is so simple I cannot believe it” come out next.

ful. I searched ZiLOG’s application notes for the XP development board, and eventually found AN0191.PDF, titled ‘Reading Temperature Using the Z8 Encore! XP MCUs.’

A companion ZIP file, AN0191- SC01.ZIP, contained the compiler project files for the temperature application. This is where I spent the most time, learning how the application worked and then modifying it to send the proper ASCII strings to the TTS256. Part of this effort required a change from ZiLOG’s standard 38,400 baud rate to the slower 9600 baud used by the TTS256. I also had to set the Flow Control parameter to None in the COM port properties.

In addition, I had to add enough of a pause between messages to allow the SpeakJet to do its talking. Sending the messages too fast resulted in dropped words, as well as portions of words pronounced incorrectly. I spun my wheels for a while trying to get the wrong project working (it was not designed for the XP) and looking at