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Circuitbenders Forum => Circuitbending discussion => Topic started by: Oceanus - XD515 on May 10, 2008, 03:13:23 PM

Title: A new sort of Bend to try
Post by: Oceanus - XD515 on May 10, 2008, 03:13:23 PM
Rather than the conventional 'short something out and see what happens' this is a little more subtle.
Most chips have a manufacturers test pin, if you get the part number off a chip and google it, you can get the manufactureres data sheet as a .pdf. The test pin is normally connected to 0v in the toy / keyboard, but if you put it to +VDD or inject audio into it, you get some very interesting results.
The Casio SK CPU's have a test pin ( pin 42 on the big SMD chip ) likewise the SK-5 percussion chip has a test pin, and I came up with the 'spacial distorter' mod based on this. Most chips do have a test pin, A/D's D/A's Mask MPU's, Codecs etc.

Attached is the info for implenting this on the SK-5 percussion chip which I hope people will find interesting!
Cheers
Paul
Title: Re: A new sort of Bend to try
Post by: computer at sea on May 10, 2008, 06:21:35 PM
I can't wait to try this out!
Title: Re: A new sort of Bend to try
Post by: Oceanus - XD515 on May 10, 2008, 06:36:37 PM
I forgot to post this,

An audio sample can be downloaded here http://www.kitapi.com/oceanus/spacial%20distorter.wav

and a picture of the finished bend :-)

Cheers

Paul
Title: Re: A new sort of Bend to try
Post by: computer at sea on May 13, 2008, 02:55:53 PM
Hmm... I can't seem to get mine to work.  I double checked both the service manual and the instructions here, but nothing really did the trick.  All I ended up with was a slight fade in volume.

Is the trimmer set to something specific and left there?
Title: Re: A new sort of Bend to try
Post by: Oceanus - XD515 on May 13, 2008, 04:28:54 PM
Hi,

If you look carefully at the picture.. you have to cut the track :-)

Cheers

Paul
Title: Re: A new sort of Bend to try
Post by: computer at sea on May 13, 2008, 04:53:38 PM
Of course!  Otherwise the test pin still goes to ground, right?

Thanks Paul.
Title: Re: A new sort of Bend to try
Post by: Oceanus - XD515 on May 13, 2008, 09:00:21 PM
Hi, that is correct.. if you do the mod without disconneting the test pin from ground, you will just get a reduced volume as you are grounding the audio output.

If you've still got your track cutting blade handy, you could try this ;-)

Pattern Mutator...

There is an 8 bit digital bus between the SK-5 CPU and the percussion chip ( basically 8 wires that send numbers in binary format, i.e. the number 10 would be represented as 00001010 and 255 would be 11111111 etc). If the SK cpu needs a bass drum sound, it places a number on the data bus, say 11001001 and sends another signal to the percussion chip to read in the 11001001 and make the noise. The percussion chip registers the number and the 'go' signal and produces a bass drum noise. The pattern mutator is simply a patch panel on the data bus between the CPU and the percussion chip, which allows us to 'modify' the number sent from the CPU, before the percussion chip reads it. For example the CPU sends 10010010, but if we swap over the first and last two bits ( by moving the wires ) the percussion chip sees 01010001 and makes a different sound. It also affects the drum pads, as pressing a drum pad makes the cpu send a signal to the percussion chip. This is also a very easy bend to implement, directly under the chip on the PCB are some nice test points ( round silvber blobs on the PCB track ) so you simply cut the track after the blob and before the pin of the percussion chip. All the wires from the blobs go to 8 patch connectors, and another 8 patch connectors are wired back to the percussion chip on the other side of the track that you cut. Then make up 8 jumper wires to connect the wires from the test blobs back to the wires to the chip pins.

Title: Re: A new sort of Bend to try
Post by: AttDestroyers on May 13, 2008, 10:53:42 PM
This is awesome. it's time to google some chip numbers.
Title: Re: A new sort of Bend to try
Post by: computer at sea on May 14, 2008, 02:33:26 AM
That's perfect, as I was trying to figure out a way to modify the bass drum sound in the spacial distorter mod.  Very exciting work you're doing here, Paul.
Title: Re: A new sort of Bend to try
Post by: gmeredith on May 14, 2008, 04:17:21 AM
OK OK this is REALLY interesting!!

Paul, regarding your comment about swapping the data messages for the drum firing - does this mean then, that it would be possible to exchange the data lines, so that, where there would normally be a hand clap in a rhythm, you can get it to be the cymbal?

I ask this in relation to my SK-8 (almost identical to the SK-5 circuit).

The SK-8 doesn't have the drum sound pads - but you can still access these sounds individually from the matrix grid, and put external switches to trigger them, just like the SK-5 pads.

The drum sounds , in this case, on the SK8 are kick, snare, hihat, handclaps.
I would like it to be: kick, snare, hihat, cymbal - because I can use the cymbal as an open hihat.

Since I have these 4 drum lines and the keyboard keys MIDI'd with a Highly Liquid MIDI SK board, it will then mean that I can finally access the cymbal over MIDI, and sequence my own rhythms with the cymbal (open hihat).

Below is the matrix table for the SK8, if that helps. Where the matrix table refers to "base" that means kick drum, not bass sound.

Is this possible?

cheers, graham
Title: Re: A new sort of Bend to try
Post by: Oceanus - XD515 on May 14, 2008, 03:45:27 PM
Hi Graham,

Yes very possible. I have sent you a .wav of various fiddlings of the patterns. You just need to identify the Byte that relates to a cymbal sounds. If you have an 8 channel logic anlayser you can hook it on the data lines and get it to strobe from the OKI chip enable pin, you will see each byte in realtime..

It is also possible to 'play' the OKI chip direct, if you connect the data lines to some SPST switches you can load up a byte i.e. 00100101 ( off off on off off on off on ) then you can fool the chip into playing whatver sound it has loaded at a specific address.

Cheers

Paul
Title: Re: A new sort of Bend to try
Post by: computer at sea on May 15, 2008, 03:59:47 AM
So I did some preliminary poking around with the pattern mutator mod and came up with some pretty ok results.  First, I put 8 switches between the test points and the spots on the chip and tried that out for awhile.  There was some decent stuff to be found just by trying out random combinations, but more often than not it produced a variant of the really busy spastic barking bend that you can find with almost any two points and a drum beat.  I got the impression that if I had a better grasp of what information was going where (or even what the most significant bit was) that I'd be able to have better control of the output.

Maybe knowing the binary numbers for different drum sounds would have helped, but I didn't know which side to read from.  I assumed that since I was looking at the bottom of the chip, the first digit would be all the way to the right, but I wasn't entirely sure.

I had much more luck wiring RCA jacks to all the points and leaving the data lines intact.  The sounds stayed more rhythmic and did some nice filter type changes without the mildly off beat stuff.

In any case, I have a happy amount of work ahead of me.
Title: Re: A new sort of Bend to try
Post by: sensor on May 21, 2008, 04:47:20 PM
has anyone tried the testpin (42) in the sk-1?
Title: Re: A new sort of Bend to try
Post by: Oceanus - XD515 on June 12, 2008, 07:16:18 PM
Hi,

Yes I've done this to an SK-1. Depending on where you connect the test pin, it will have a nice boomy effect on the drums, or other wierd randomness. I do have a .wav sample but it is to big to attach on here. I can mail it to you if you want to hear.

Cheers

Paul
Title: Re: A new sort of Bend to try
Post by: sensor on June 18, 2008, 02:30:19 PM
yes this was pretty cool. and please explain what kind of connections you've made.
thanks a lot.

matthias
Title: Re: A new sort of Bend to try
Post by: sensor on July 08, 2008, 01:57:59 PM
oceanus?
Title: Re: A new sort of Bend to try
Post by: Oceanus - XD515 on July 08, 2008, 03:53:54 PM
Hi,
Sorry I missed your last post.

I connected the test pin to the Perc audio out ( pin 97 ).
Here is a complete list of all the SK-1 / 5 CPU pin details:

CASIO SK series CPU chip pin details         

Pin(s)   Name   IO   What it does
1   BGND   Supply   Ground or 0V supply for the A/D within the CPU
2   VACD   Supply   Neg 5v Supply for the A/D within the CPU
3   W-Noise   unknown   W-noise pin Currently not used on the SK-1
4   M-Noise   unknown   M-noise pin Currently not used on the SK-1
5-11   IO0 - IO6   Bi Direct   7 data bus lines used to send / receive data from ROM and RAM
12   A0   Out   Part of Address bus - A 0
13   IO7   Bi Direct   Remaining 8th line for Data bus ( see pins 5-11 )
14   A1   Out   Part of Address bus - A 1
15   CE   Out   Chip enable signal for the CPU to select either ROM or RAM
16-18   A2,A10,A3   Out   Part of Address bus - A2, A10, A3
19   OE   Out   Output Enable signal to allow the RAM to put data onto data bus
20-30   A4-9, A11-15   Out   Rest of Address bus A4-A9 and A11 - A15 (sixteen lines in total )
31   WE   Out   Write Enable signal. When Low the CPU writes data to the RAM
32   RFSH   Out   Refresh Signal output. When Low the CPU refreshes Ram
33   TIN   In   Not used on SK-1 Pulled to VDD2, maybe a Test pin
34   TC0   In   Not used on SK-1 Pulled to VDD2, Some sort of bit input
35   TC1   In   Not used on SK-1 Pulled to VDD2, Some sort of bit input
36   TOUT   Out   Not used on SK-1 Pulled to VDD2, Something to do with TC0 and TC1
37   ADCTR   In   Not used on SK-1 Pulled to VDD2, Something to do with internal A/D
38   WE   Out   Write enable signal, not used on SK-1 but for driving extra devices
39   CE   Out   Chip enable signal, not used on SK-1 but used on SK-5 to drive Percussion Chip
40   GND   Supply   0V supply for the CPU
41   CE2   Out   2nd Chip enable Signal, unused on SK-1 but used on SK-5 to drive Demo Rom Chip
42   TEST   In   Test pin, worth experimenting with!
43   VDD1   Supply   Neg 5v Supply for the CPU
44   VDD2   Supply   Used to connect the Unused pins to a voltage source Internal analogue Ground
45   POFF   unknown   Power Off? Not used on the SK1 or SK5
46   C1   Out   Not used on SK-1, left floating but used on SK-5 as clock for Demo Rom
47   C2   Out   Not used on SK-1, left floating but used on SK-5 as clock for Demo Rom
48   OP   Out   Not used on SK-1, left floating but used on SK-5 to select between data / address on Demo Rom
49-56   Aux D0 - D7   Bi Direct   Secondary data bus D0 - D7. Unused on SK-1 but drives SK-5 percussion Chip / Demo Rom
57   OSI   In   Master clock oscillator inputs for 7.24Mhz oscillator
58   OSO   Out   Master clock oscillator output for 7.24Mhz oscillator
59   MI   In   Not used on SK-1, left floating but used on SK-5 as input for Power on Detector circuit
60   RESET   In   Reset in put signal. Pulsed high it will initialize the CPU
61   K015   Out   Control signal for external filter circuit, not used on the SK-5
62   K014   Out   Not used on SK-1 but determines Accomp volume control signal on SK-5
63   K013   Out   Not used on SK-1 but used as RAM / ROM select signal on SK-5
64   K012   Out   Not used on SK-1 but used as Auto Power of signal on SK-5 ( pin 86 om SK-1 )
65-76   K011 - K0   Out   Key Out signals used to scan the Keyboard and Buttons (K011, K010 unused on SK-1)
77-84   KI1 - KI8   In   Key and switch input signals
85   PO0   Out   Not used on SK-1 but used as a Reset signal for SK-5 percussion Chip
86   PO1   Out   Auto Power Off, when Low switches off the power supply. ( cut this to keep power on )
87   PO2   Out   Unused IO pin for both SK-1 and SK-5
88   PO3   Out   Control signal for external filter circuit, not used on the SK-5
89   EH   Out   Analogue Envelope control signal for Melody channel ( CH1 )
90   EG   Out   Analogue Envelope control signal for Obbligato channel ( CH2 )
91   EF   Out   Analogue Envelope control signal for Chord channel ( CH3 )
92   EE   Out   Analogue Envelope control signal for Bass channel ( CH4 )
93   SH   Out   Analogue Audio Pitch signal for Melody channel ( CH1 )
94   SG   Out   Analogue Audio Pitch signal for Obbligato channel ( CH2 )
95   SF   Out   Analogue Audio Pitch signal for Chord channel ( CH3 )
96   SE   Out   Analogue Audio Pitch signal for Bass channel ( CH4 )
97   SC   Out   Analogue Audio output for Percussion sounds, not used on SK-5
98   AGND   Supply   Ground or 0V supply for the D/A within the CPU
99   VDAC   Supply   neg 5v source for D/A within the CPU
100   VIN   input   Sample sound data enters the CPU here

Hope this is useful!

Cheers

Paul

Title: Re: A new sort of Bend to try
Post by: mikebike on January 06, 2011, 05:08:50 PM
FIRST POST! (awesome forum everyone!)

i just started the drum mutator mod, with the 8bit bus.

i was wondering, would it be possible to use an inverter chip to change the state of the bits?

so 01100110 = 10011001?

possibly, we could use a switch at each pin to decide weather its inverted or not?

i dont knwo anything about digital logic, but from what ive read i thoguht it might be interesting

keep up the good work!
Title: Re: A new sort of Bend to try
Post by: Gordonjcp on January 06, 2011, 05:24:06 PM
You could do.  If you use a pair of quad XOR gates, you can see how you could use a switch to flip between inverting and non-inverting.
Title: Re: A new sort of Bend to try
Post by: mikebike on January 07, 2011, 09:47:07 PM
i did a pictorial of this mod on the EA forum:

http://experimentalistsanonymous.com/board/index.php?topic=2528.msg13531#msg13531 (http://experimentalistsanonymous.com/board/index.php?topic=2528.msg13531#msg13531)

hope this helps anyone having trouble
Title: Re: A new sort of Bend to try
Post by: Simon Vactrol on January 09, 2011, 10:32:35 PM
Great!! thanks Paul!
Gonna go mark 2 on my SK5 tomorrow!!
and give a go to those modifications.
 :)


Simon.
Title: Re: A new sort of Bend to try
Post by: mikebike on February 28, 2011, 06:04:52 AM
not paul, im mike, haha

im working out the inveter thing, witch i hope will be as versitle as the patch cables, with out the need for cables.

thinking about a hex shmitt trigger with switches and possibly some gate circuittry. keep ya posted