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Talker/80 for the TRS-80 Model 1, 3, and 4

Talker/80 - New Dimensions in Voice Synthesis for the TRS-80

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Talker/80 is a new speech (voice) synthesizer for the TRS-80 Model 1, 3, and 4! It offers DECtalk-based natural sounding speech, and can emulate the "official" TRS Voice Synthesizer as well as the VS-100 Alpha Products voice synthesizer. The original software runs without changes / patches. Both the VS-100 and the TRS Voice Synthesizer utilized the Votrax SC-01 speech chip. The SC-01 is "emulated" by means of DECtalk here (phoneme mapping).

An Iconic Computer & its Voice Synthesizer(s)

Update: #SepTandy entry - DIY Talker/80 kit assembly for the Model III / Model 4!

I am proud newbie owner of a Model 1 since January 2020. I always wanted to have one of these - a member of the 1977 Trinity that started the home computer revolution!

Well, after acquiring 2 untested Model 1 (one from Etsy, one from Ebay) for little money, both requiring 3 weeks of rather intense refurbishment work (including fixing the internal 5V power supply, replacing the 12V overvoltage protection Zener diode, replacing some bad RAM chips, upgrading to Level 2 1.3 ROMs to fix keyboard bouncing problems, getting the FreHD dual boot EPROMs installed, the flex keyboard cable replacement, removing some bad Alps keys, and so on), and the addition of an Extension Interface allowing me to connect my HxC and a real floppy drive to it, finally, after 2 months of work I had 2 fully functional, fully upgraded Model 1. Of course, I also had to install the Lower Chars mod. The Expansion Interface and its ability to display 64 characters per line on a sharp monochrome monitor, combined with the very good Alps keyboard in one of my machines, makes the Model 1 quite useful for text processing. IMHO it provides far better utility for business applications than the other early 8bit machines of that  - and later - time; the exception maybe being the Amstrad CPC with its 80 characters per line and CP/M capabilities, but the CPC came almost 8 years later.


Being a fan and collector of vintage speech synthesizers (I must have one of the biggest collections in the world by now...) I REALLY wanted to add the TRS Voice Synthesizer to my setup. But they are scarce, and the last one I saw sold for over 400 $ on Ebay... I am crazy, but not that crazy. So, I thought, if I cannot get the real thing, then at least let's try to port my LambdaSpeak speech synthesizer for the Amstrad CPC to the Model 1. Both the TRS-80 Model 1 and the Amstrad CPC are Z80 machines, but the official vintage speech synthesizers used different chips.

The TRS Voice Synthesizer uses the Votrax SC-01 speech chip, which is unobtainable these days (and single vintage SC-01 chips, if they show up, sell for > 100 $). For LambdaSpeak, I had emulated the GI SP0256-AL2 vintage speech chip - this chip was being used in the "official" CPC speech synthesizer, the Amstrad SSA-1 and the DKtronics synthesizer. I emulated the SP0256-AL2 using DECtalk, by means of a "SP0256-AL2 allophone to DECtalk on the fly phoneme mapping". This works surprisingly well for the SP0, and produces better and more understandable speech than the original. Now, I figured I could do the same "on the fly phoneme mapping" for the Votrax SC-01 and hence implement a TRS Voice Synthesizer emulation. And at the same time, also emulate the other popular historic TRS-80 speech synthesizer, the VS-100 from Alpha Products. 

Now, for LambdaSpeak the SP0256-AL2 emulation was a bit easier to achieve, given that I have the original SP0256-AL2 (and Amstrad SSA-1 speech synth that uses it) at hand. But I never even saw a Votrax SC-01. Not even from the distance. But I have the TRS Voice Synthesizer Software, and the VS-100 software. Thanks to the guys on the Vintage Computer Forum, I got some technical information regarding the SC-01 phoneme set, and the mapping of the TRS Voice Synthesizer "ASCII phoneme character set" (a TRS invention) to the SC-01 phonemes. Now I only needed to figure out how to map the SC-01 phonemes to DECtalk phonemes, which required a bit of trial an error.


The SC-01 Phonemes are documented in the Votrax datasheet, and here are the "ASCII" TRS Voice Synthesizer phonemes for some of them - thanks a lot to "Joe Zwerko" (I guess this is not his real name) from the Vintage Computer Forum for providing this scan:

So, roughly, this SC-01 Phoneme mapping to DECtalk ARPABET goes as follows: 

void init_allophones(void) {

  // VOTRAX...
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Talker80-databus.jed

Databus Tristate Buffer JEDEC file (for G540 EPROMer or similar)

jed - 2.10 kB - 05/02/2020 at 04:59

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Talker80-decoder.jed

Address Decoder JEDEC file (for G540 EPROMer or similar)

jed - 853.00 bytes - 05/02/2020 at 04:59

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Talker80-databus.PLD

Databus Tristate Buffer WinCUPL Source File

pld - 990.00 bytes - 05/02/2020 at 04:59

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Talker80-decoder.PLD

Address Decoder WinCUPL Source File

pld - 2.15 kB - 05/02/2020 at 04:59

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Scan.jpg

TRS 80 Voice Synthesizer "ASCII Phonemes" for some of the SC-01 Phonemes

JPEG Image - 136.82 kB - 05/01/2020 at 15:41

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  • 2 × GAL22V10 Logic ICs / Programmable Logic: PLDs
  • 1 × Atmega 644-20PU Microprocessors, Microcontrollers, DSPs / ARM, RISC-Based Microcontrollers
  • 1 × 40 Pin Ribbon Cable Connector to the TRS-80 Model 1 Expansion Port. About 8 inches?
  • 1 × Crimp 40 Pin Edge Connector For connecting to the Model 1 Expansion Port.
  • 1 × 40 PIN IDC Box Header Backside of Talker/80, cable connection to the Model 1 Expansion port.

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