Thursday, March 27, 2008

Say What?

Here's how to interface an ancient, 80's era, General Instruments SP0256-AL2 speech synthesizer chip to a Basic Stamp 2 so you too can give your robot the gift of virtually unintelligible, vintage, synthetic speech! (Listen closely to the audio clip and you can almost make out, "Hello world")

Audio Clip

Data Sheet:
See previous SP0256-AL2 post to download the data sheet.

Circuit Diagram:
sp0256-al2.sch


Note: the LM386 amplifier circuit provided in Robot Builder's Bonanza just wouldn't work. It differed slightly from the one presented in the data sheet. The data sheet circuit is pictured above, but with the addition of a giant 100uF power decoupling cap; the LM386 was apparently drawing enough current with the speaker attached to cause the BS2 to reset similarly to prior motor control problems. A somewhat smaller cap doesn't seem to work -- more investigation needed. The potentiometer above is actually not installed yet; a resistor is in place to prevent clipping that was showing up on the o-scope.

The Code:
SP0256AL2.bs2

' {$STAMP BS2}

' {$PBASIC 2.5}

' SP0256-AL2 Speech Chip
' Control Code

' Text: HELLO WORLD.
' Phoneme: HH EH LL AX OW (PAUSE) WW ER1 LL PA2 DD1 (PAUSE)
' Octal: 033 007 055 017 065 003 056 063 055 001 025 004

' Dec: 27 7 45 15 53 3 46 51 45 1 21 4

text DATA 27,7,45,15,53,3,46,51,45,1,21,4,0
ptr VAR WORD
char VAR BYTE

setup:
' P7 <- SBY ' P6 -> 'ADL
' P0-P5 -> Data

DIRL = %01111111
HIGH 6

ptr = text

PAUSE 2000

go:
' Set char to the next phoneme
' Send it

READ ptr,char
DEBUG DEC char, CR
IF char <> 0 THEN cont
END
cont:
GOSUB pout
ptr = ptr + 1
GOTO go

' Phoneme Output
pout:

' Now just set OUTL P6='ADL=1, (P0-P5) = phoneme byte

OUTL
= char | %10000000
DEBUG BIN ? OUTL

' And set P6='ADL=0 for 2usec to tell the chip to read
PULSOUT 6,1

' Wait for P7=SBY (standby) to indicate chip is done speaking
notdone:
IF IN7 = 0 THEN notdone
RETURN

Quick Code Explanation:
The data sheet goes into this in detail, but in short: the program puts the 6-bit phoneme data on data lines A1-A6, then pulses ^ALD low for a short time to let the chip know data is ready, then polls SBY until it goes high, then repeats until it runs out of phonemes.

That's it. This is just a prototype so there's lots more to do before this becomes useful. For example, wouldn't it be nice if a handy dandy AVR of some flavor could front end this chip and accept data over serial and/or I2C? Maybe even do true TTS?

3 comments:

  1. truely amazing!

    look at the bright side... in 20 some years, there's bound to have been some progress right? microsoft sam? eh I guess not... ;)

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  2. First, thanks for this. I have a few of these chips around. First one I bought years ago at RS.Grabbed the others on a discount/clearance table at RS also. One I have from a Coleco Speech Unit.

    I originally was going to interface one to my SX-64 (which I still have and works). I really would like some help on an RS-232 interface for one of these.

    One or two of the packages has a speech ROM included with the AL2...

    :)

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  3. Jack,

    Thanks for the note!

    Cool you still have an SX 64. I vaguely remember them, must be kind of rare? I can help with an interface to the 64 if it uses a similar connector to the C64; I can dig up some pics / instructions for that.

    Re: RS232 -- happy to help if I can. Since the SP0256 takes parallel data, the trick is to convert parallel to serial, and also to set up a proper RS232 receiver.

    MAX232 is an RS232 driver / receiver chips out there that do proper voltage levels -- datasheet: http://www.atmicroprog.com/download/ci/max232.pdf So that should take care of the reciever side.

    For converting serial to parallel, there are some chips that will do this, tho I can't think of any off the top of my head. Some googling will probably turn something up. Then it is a question of wiring in the various control pins on the AL2 appropriately...

    Let me know how I can help... (send me an email...)

    Michael

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