chipspeech Diary, Part 2

Last summer I spent a good part of my late night research time on Texas Instrument Voice Synthesis Processor (VSP) LPC10 decoding chips. TI made LOTS of these from the late 70s to the late 80s, both for the OEM market and for its own use, under different names. They usually prefixed them TMC or CD for internal use, and TMS for OEM use, but their naming was not always consistent, which leads to lots of confusion.

The goal for chipspeech is to playback LPC10 streams coming from any Texas Instrument device/software and to do so in a sample accurate manner.

We are very close to that goal, but since I found no less than 8 variants of VSPs - all of which had to be accounted for in my emulation core - I'm convinced in fact, that there may be more.

A variant is a unique combination of the following features:

• Pitch encoding format (5 or 6 bit indexes)
• Energy ROM look-up table
• Pitch ROM look-up table
• K (lattice filter) ROM look-up table
• Voiced chirp ROM look-up table
• Variable frame size (TMS5220 rev A and up)

Those are the main characteristics which can quite significantly alter the tonal quality of the output voices. For instance, if you play a stream made for a variant on another variant you could get anything from a slightly unusual nasal quality playing certain words of phonemes, to a completely alien-like version of it, to typical circuit bending whooshes and 'blurps'.

We could have created even more sub categories to account for other observed behaviors, like for instance what happens when an unvoiced (noise) frame is followed by a silence frame (Energy either fades or not). There are probably even more subtle differences especially considering the influence of the various internal interpolation stages 'shifts' depending on the chip - but nothing that you could easily hear I am willing to bet.

The following is a list of VSPs found in devices that we have acquired and dismantled (some of which are incredibly rare). This list is by NO means complete as we do not have infinite resources... nor storage space :).  And I do plan on revisiting this as new discoveries are made.

TMC0280/CD2801 were found in:

• Language Translator/Language Tutor (same thing)
• Speak & Math
• Speak & Read
• Speak & Spell (UK, that's why the US carts sound funny with it)

TMC0281/TMS5100  were found in:

• Speak & Spell (US - Buttons)
• Dictée Magique (French Speak & Spell)
• Speak & Spell (Japanese - Buttons)
• Century 'Dazzler' CVS arcade PCB.

TMC0281D/TMS5100A  (Energy table changed from the previous) were found in:

• Speak & Spell (US - later membrane)
• Speak & Spell (US - Compact)

TMS5110 (A/C) Found in:

• Stern/Valadron Bagman PCB
• Chrysler Electronic Voice Alert
• Coleco Talking Teacher/K28 Talking Learning Computer (not the Votrax one)

CD2802 Found in:

• Touch & Tell
• Vocaid

CD2501E/TMS5200 Found in:

• TI99/4A Speech Adapter

TMS5220 Found in:

• IBM PCjr Speech Adapter

TMS5220(A/C) Found in:

• Magical Wand Speaking Reader (A rev)

How I categorized the variants:

A) Made a full regression test suite of LPC10 streams, each testing a different edge case. I send the streams to the VSPs, record and compared results.

B) Dumped the internal ROM tables of the chips. When idle, VSPs serially output the current values for Energy, Pitch and K's on its PROMOUT pin.  We can thus read the internal values of the internal ROM tables again by crafting custom LPC10 streams where each and every possible values of Energy, Pitch and K entries are set in succession. But we need a different stream for 5 and for 6bit pitch variants, of course!

Logic analyser dumps of ROMCLOCK,T11 and PROMOUT running these streams were then analysed with custom code, then text editor mangled and compared against each other. (Thanks to Lord Nightmare for the explanation of the PROMOUT logic!)

Each TMS51XX/5bit style chip was placed on a Stern Bagman PCB with a customized EPROM @ 9T, offset 0x1032, BIT6 "channel", replacing the French "Aye Aye Aye", (death sound) with the custom LPC stream. Since there are two form factors for those chips (DIP and SDIP), a ZIF adapter was used when needed:

Each TMS52XX/6bit style chips was placed on a custom made protoboard with custom FTDI programs to send the LPC10 stream using the 'Speak External' command

Portions of this research was contributed to MAME/MESS and hopefully will be used for the introduction of the various Speak & Spell drivers that they are working on.

chipspeech Diary, Part 1

In case you haven't noticed, we take hardware research and emulation very seriously here at Plogue.

-We never take any information for granted, whether its from official datasheets, patents or third party research.

-We always double check and investigate what we do on hardware: creating custom tests suites for each and every chip, sending values and capturing the results digitally.

-We then create models and iteratively refine them as we add new tests, often for virtually every possible edge case there is.

You can imagine that this is a long, VERY long process. We sadly never know when our products will ship because simply knowing how an integrated circuit works in and out does not magically make it a product! (stating the obvious)

We started this project 8 years ago but it really started kicking into speed in the last 3. Back then there wasn't a single 'speech chip' plugin out there(at least I think). And there is now a handful of them, and STILL we are not ready to party with the rest of them.

We hope that this new blog series will help you wait a little bit longer for what we hope will be the one that sets the standard, like chipsounds did.

PART1:

It all began with gathering, or more like compulsive hoarding of nearly every vintage consumer device that talked. We set our start point to 1975,  the date where the first ever speech synthesizer IC reached the market, the TSI Speech+  up to the dawn of the 90's where essentially everything went boringly intelligible. 

How many devices are we talking about?
Quite a lot actually.

Plogue livenes

Is a Nintendo Entertainment System "homebrew" application that I've developed in order to improve the emulation of the RP2A03 for chipsounds 2.0, which is currently in development.

It allows you to change the values of the APU's memory mapped registers ($4000 to $4017) using nothing but the Nintendo d-pad.

A side effect is that it can also be used to generate live minimalistic 'music' on a NES by manually toggling a bit at a time, which is of course completely unintuitive!

Changing the pitch value for a specific channel on a musical scale implies changing multiple bits at once, something that is clearly impossible here.

As I like a challenge, I tried to see if I could make something remotely musical out of this incredible restriction set. The following piece was recorded live (not sequenced in any way) on a real NTSC NES:



Note:
A)The main DMC 'sample' that starts the piece is actually the application code and graphics being interpreted as Delta Modulation.
B)My NES is stereo mod-ed, so there is a slight touch of post mix and reverb, but that's it.

If you want to try it our for yourself you can download the latest .nes ROM here

Revision history:
1.1 Fixed the wrap around on the lower part of the screen
1.0 Initial version

How can you run this on a real NES and not just in an emulator?

1)Put it on a Powerpak
2)Make yourself a nice UNROM (Mapper 2) dev cartridge out of one of those carts
(mirroring is irrelevant). I won't get into the details of that, but here's what mine now looks like:

chipcrusher re-sampling vs frequency response

Quite a few users have complained about chipcrusher's peculiar 'dry' frequency response compared to what they get with other common decimator plugins. This post hopefully will explain a few things.

Lets say we bypass the bit reduction, distortion and post filtering and only concentrate on the task of downsampling the plugin's input signal. which would be say at 96kHz. and that chipcrusher's re-sampler would be at 44.1kHz, its internal maximum.

There are two important aspects to consider:

1)Typical results achievable using a vintage sampler is very different from 'your typical Bitcrusher VST'.

99% of bitcrushers/decimator plugin out there use the same tired algorithm that was posted more than 10 years ago on musicdsp.org. This method does NOT band limit the input signal prior to the downsampling, it just sample and holds using a counter... any sample!

This is not what classic samplers did. Any engineer with half a brain at least tried to filter analog audio signal so it wouldn't contain harmonics over the Nyquist frequency of the target sample rate!. If you skip this pass, you will get extra aliasing all over the spectrum.

2)Not all lowpass filters are created equal.

All versions of chipcrusher prior to v1.005(available soon) used a CPU friendly downsampling setting which - in retrospect - might not have suited everyone's taste since it was not steep enough for high frequency content.

You can see chipcrusher's default precision somewhere in this animation made using 96kHz -> 44.1kHz with a white noise as source. All the other settings will be available. We have added a new 'Precision' parameter to set the steepness/cpu use ratio you desire. BTW The first picture in the lot is from a "do not pre filter" setting, we offer 6 such settings, from 6 point spline to truncation. Aliases like crazy, but to each is own.

Making arcade cabinet impulse responses.

Here are a few pictures we took while capturing impulse responses for chipcrusher in late 2011...
Sorry for the mess, our office is a perpetual hardware dismantling lair.

GBA SP Speaker Impulse Response

Looks fun? This is what I did for each and every speaker impulse in chipcrusher's Post Processing section.

The goal is to capture not only the frequency response of the speaker itself, but also the effect of its casing and internal components: resonance, cancellations etc.

Its thus very important to make sure to properly close the unit (which can be complicated by the tight confined space) with your soldered speaker leads dandling out without changing the tonal balance of the unit.

A few carefully created test tones are then 'injected' through the leads and recorded with one or more microphones in a mostly anechoic space at a few inches from the device. 

Next the recordings are processed with custom software.

Once thats done, and we are sure the recorded IR data is valid, we need to do the inverse: reopen, unsolder,
close and make sure it works. While the microphones are set up I usually also record native console sounds (games or test code), through that same setup, for later comparison.

Luckily no unit were destroyed, and everything worked just like it did before.

(But you can imagine the stack of devices that I have in the office and in my basement)... there is a psychological condition for that, and also a TV show about it.... Rest assured I ONLY keep tech stuff. :)

Soldering '80

This is pure nerd porn, in so many ways.
And there's a whole lot more here:

https://www.youtube.com/user/paceworldwide?feature=watch

Galaxian's digital oscillator explained.

The Namco Galaxian arcade PCB generates a few different types of sounds:

1. Analog Fire sound.
2. Analog Explosion sound
3. Three Analog 'Rack Noises' (alien drones)
4. Monophonic Digital Oscillator, which does the quirky intro tune and the aliens being destroyed.

The latter being digitally controlled and generated, it makes it a perfect candidate for the chipsounds bandlimited oscillator generators. The following explains how the digital part is generated:

First, a variable speed pulse is created by using two cascaded 4-bit counters (74LS161) (B). The input clock (2H @ 1.536MHz) is divided by a variable amount according to the last 8-bit value received from the 74LS273 (A)  flip flop. This is done by the Z80 CPU (which runs the game code) when it indirectly sets the !PITCH signal and the required pitch value into the "I/0 & Ram Data Bus" by writing to a specific address in external memory.

This pulse then drives pin 13 of a 74LS393 binary counter (C) which in turn outputs a 4-bit (16 step) binary pattern: 0000, 0001,0010,0011,(...),1111  or  0,1,2,3,(...),15 in decimal.
If those 4 output bits were to be sent to a 4-bit DAC, the result would have been a pretty standard saw waveform with no volume control. But this is obviously not what the Namco engineers wanted...

In this particular design, only 3 output bits of the '393 are used (QA, QC and QD, but NOT QB).
Resistors (D) (15k, 22k, 10k and 33k) are inserted onto the bits to create a weird R-2R 'esque ladder DAC. Also some 'components' of the signal are only added into the DAC depending on two extra
CPU controlled bits (Vol1 and Vol2).  Each driving two of the four available analog gates in the 4066 (E)

If you are following so far you understand that this can generate 4 different waveforms. Once you know this, its relatively trivial using voltage divider maths to figure out what those waveforms would look like.
I used an excel sheet for these maths:

From tests on my board the Vol1 bit is always 0 during gameplay, so logically only the [0,0] and [0,1] waveforms are actually ever used in the game. My guess its that vol1 never gets to be 1 to match the volume of the analog sounds this PCB also generates.

I successfully compared the two available waveforms with actual recordings of the board:

And they were included as oscillators definitions in chipsounds 1.6 under "05 - Arcade/Galax"

Namcot163 Dual 27C020 Eprom Cart

NES eprom carts

Clockwise from top:

1)Esper Dream 2 Aratanaru Tatakai, Famicom, VRC6, mapper 26, can use regular 27C020 EPROM
2)Lagrange Point, Famicom, VRC7, mapper 85, can use regular 27C040 EPROM
3)Castlevania, NES, UNROM, mapper 2, needs modification to use 27c010/27c020 eproms
4)Super Mario Bros, NES, NROM, mapper 0, no mods needed

Currently using 1 and 3 to run tests for my next updates.
I would also need to add my Dragon Ninja NAMCOT-163 (iNES Mapper 19) in there, but I didnt eprom-ise it yet.

Address Sniffing an EPROM

New Scope

Can't wait to put it to good use. Its a major step up from my crappy PC-based USB scope. Thanks to EEVBlog for the great review.

AY8930 Initial tests!

Over concerns received about the possibility that the chips were fakes I decided to test a few of them right away  (Paypal customer is always right no? I might just get my money back if they are fakes)

So first thing I did was to place two of those chips on my Bagman arcade board, and the sound was just as one would expect a normal AY-3-8910 (the old version). So at least they are not broken CPUs or whatnot.

The concerns raised by my colleagues pointed towards  the possibility that these were just re-branded AY-3-8910 and not AY8930's, based on the date code (2008?? if 0830 is a date code I would admit its odd for a chip designed in 1990) and on the peculiar look of the Microchip logo, also that "TAIWAN Microchip" was weird and unseen before. (though this and that beg to differ).

So I undusted my AY protoboard that I used for chipsounds research, and placed a AY8930 that was previously tested OK in Bagman. Tried a few VGMX log files, (including intv_lock_n_chase.vgmx - one of my favorite games)

First interesting discovery was that the chip didn't seem to run at 3.57MHz but at half of that (1.79MHz, just ok for the right pitch of the intv register dump). I forgot that my protoboard was last populated with a YM2149F, which uses pin 26 for clock divider (input). and my jumper was already shorted. So at least if this is a rebranded chip, its a rebranded YM2149F and not a bare AY-3-8910, since the 8910 doesn't have this feature.

Started to check out the datasheet and made a little test VGMX file that plays a simple tone and pass through
A) all 32 values of volume
B) all 8 values of Duty Cycle (PWM)

Here's a lame 'instant video' of my setup and playing both Lock 'n' Chase and then, my test file on my protoboard:



The duty cycle changes are sadly NOT seamless. This is mentioned in the datasheet as well. "The new duty cycle value will take effect immediately. This may result in one period with a "random" duty cycle at the time the register is updated."

So much for maxYMiser -alike PWM without 90% cpu usage and/or IRQ reset tricks...

I haven't yet tried the advanced LFSR noise, but I'm pretty sure this batch of chip is legit. It wouldn't make sense to copy such a chip design when theres no real demand for it. Anything is possible though....

Until next time!

AY8930 sourced!

The AY8930 Enhanced Programmable Sound Generator is a very rare Microchip (who bought GI) version of the AY-3-8910. It includes better frequency range, noise, PWM and independent control of the envelope for each channel.

I was lucky to find a stash of those chips and will soon try them on my AY-3-8910/YM2149F protoboard to see if they work and experiment with them, then for a future addition to chipsounds.

As far as the interwebs are concerned it only has been used in one PC card (Covox Sound Master+) and one game (Where in Time is Carmen Sandiego). So my job will be to hack dosbox into spewing the register writes it sends to this chip and I'll make a render using my board (the usual stuff).

Since I have now too many AY8930's to care, if you are interested in upgrading your MSX, ST or whatever (untested), this might be your chance, since I will put a few of these rare babies on sale after they are tested.

JAMMA Space Invaders experiment.

33 years ago a game caught the eyes (and ears) of many people in Japan, and later everywhere else. You can read the whole story here of course, but this is not the subject of this post.

This post is about a little experiment I made in fixing and converting an original Midway Space Invaders motherboard to run in with JAMMA harness or standalone machine.

A Few notes:

-The coin input, and controls are all mapped.

-The video is now RGBS (same signal send to R, G and B, and sync tapped from somewhere else.

-The only thing that doesn't follow the JAMMA spec is the audio output, since my mod requires a separate amp (like many other games like all Nintendo stuff and Mr.DO), so its obvious that any collector has those already. The SI daughterboard requires raw 18V+center tap directly from the transformer which I don't have (using a standard PC psu here)

-Game now uses one 27128 EPROM and not 4 to 8 separate 2716 (9316B or whatever)

-No color overlays .. duh!

Arcade Restoration - Week1: Acquisition

Wednesday Max and I went on an econoline field trip to bring back two classic cabinets in fair condition.  

I will show our restoration progress in here as time permits. Work will progress slowly since this is really a pet/coding break/lunch break project for us.