Possible Big design prob found

Argh ...
After reviewing schematics (to adapt them to the teensy) i've found a possible design bug in the schematics.
If my tought are right, i would not be possible to stop the transistor to saturate.


So imagine few values :
Speak and Spell battery + 5V (when Batteries are not new)
Speak and Spell battery : - 12V
Arduino out 1: 5v / 0 : 0V

So when Arduino output =0 , the transistor will saturate and you will 5V on the Speak and Spell BUS
When Arduino output is 5V, the transistor will stop saturate (VBE-0V)and  you will get -12V on the S&S Bus
Everything is fine..

BUT if you put new batteries on the Speak and Spell then the VBATT + is ~ 6.5 V. So  to stop saturate the Transistor we should have min 5.8 V on his base. (VBE 0.7 V).

We have few option to correct this :
- Use darlington transistor (VBE 1.4) 
- Connect Transistor emmiter to regulated 5V supply
- add a diode + a 5V1 zener on emitter of the transistor.

The PCB has been sent to Prod and they are not arrived yet.. and i''ve already spotted a design error.
Why i didn't spotted this during the testing .. ? because i'm using old batteries .. and Speak and spell Battery voltage is 5.3 V. Grr.......

Speak and Spell LFO

Still waiting for the S&S interface PCB to arrive from production, i started to build new Speak and Spell features.

I decided to create a PCB of the well known Casper Speak and Spell LFO who add a LFO to the pitch.
See the source at : http://casperelectronics.com/finished-pieces/speak-n-spell/speakspell-bending/
To add some digital feature to this, i was thinking of Digital potentiometer for the LFO controlled via Midi.. but it is another story.

Schematics:

PCB :

3d Preview :

new Schematics / Edit : Last update 1st nov.

The new schematics, with the midi input and output for the shield
The PCB has been sent to production, i should get them in 10 to 15 days.. 
the PCB will be based on this schematics:

1/12/11 : Schematics Removed, will add them again with the corrected one..
Feb 12 : Last Schmatics are on googlecode.

PCB should look like this..:

And finally the Eagle 3d Preview  (wihout midi connectors) :

autoshutown 2 the return

Finally i got the reset of autoshutdown working .. (need to verify but don't know how to do a midi note every 20 sec without doing it manually).

When pressing the "erase button" it connect the pin 6 to the pin 33 in the microctronller (via the membrane keypad), the pulse shown in the previous post will output from pin 33 and goes in the pin 6.

After few tests the conclusion is :  needed to recrate this pulse and it need to be well synced with the signal from pin 6. Using port maipulation i get env, 500 ns difference between the received pulse and the created one.
Normally this pulse should simulate a "erase" keypress and erase the screen if you press a letter button before.i execute the function (generate the pulse after every midi note) and strangely it does not erase the screen each time .. but seems to reset the autoshutdown counter correctly. To be sure it will erase the screen i should do a few of theses pulses, be they appear each 7,x ms , so if i want to put 4 pulse it will take approx 30 ms, after each midi note, which is far too much i think if you want to trigger the note quickly (not sure the S&S will accept not ever 20 ms need to be tested). i prefer to keep responsiveness of the S&S.


I also tried something totally different, remove the negative voltage from the interface and replace it with the GND, it should work in theory because the bus should have pulldown resistor.
Result  : it works , yeah .. but with some interference on the VFD display.

With the negative voltage
 correct screen with the underscore (the ctl8 pulse is due to this underscore)








 



Without negative voltage  you get strange display but works.

I'm tired of all this cable and stuff
 that's why i'm designing a sort of shield (smaller one)for arduino, once done, will sent it to a PCB prototyping service.
This shield will be usable to the arduino to S&S interface, will power the arduino with S&S batteries, it could also be used as a midi shield.

autoshutdown

The Speak and spell got a anoying feature, the autoshutdown when no button is pressed.
By using the arduino Speak and Spell interface, we inject signals directly into the speech synth and not using any button. So the Speak and Spell will power off after few minutes.
We will need to add a "automatic button press" when a midi note is played to ensure the device does not power off. For example the "/" or "erase" on the keyboard don't do any sound ..  sounds the good key to use ..

First find the connection on beetween the CPU and the keyboard :
 Keyboard connector pin   ->  CPU pin
1   ->  2
2   ->  6             used for the "/" or erase key
3   ->  5
4   ->  33           used for the "/"or erase key 
5   ->  32
6   ->  Vbatt+
7   ->  31
8   ->  30
9   ->  34
10   ->  29
11   ->  28
12   ->  4
13   ->  3

Next step watch the signals ... on the Cpu pin 6 = nothing interesting.
on pin 33 .. a pulse of approx. 500 uS.

So will check if generating a pulse will do the job of if the pulse need to be correclty timed and triggered..

First Midi test

Midi support is working fine now. Only Note On for the moment ,I need to add the pgm change to change bank of sound.becaus theoretically i can have 16383 different address. (14 bits address 2 bit for Rom chip select, 2 unused = 20 bits = 5 x 4 bit nibble)

It currently doing sound with "Note off" (because my M-audio keyboard doing Note off with a Note On velocity 0 ) will be corrected tonight.
Sorry for the Video quality and the crappy sound, it's recorded with the internal Cam/mic of my Macbook)

Code will be published soon, i need to clean it..

Midi on the way .. usb midi S&S for the future ?

I've added midi basic support and it works.
I still need to manipulate some bits to create correct mapping on midi notes and S&S addresses. but i's responding to midi keypresses :)

I also received my new geek toy, a teensy 2.0. which support USB directly. i will try to make it work with the Speak and spell. to get a USB Midi speak and spell, sounds fun .. 

I'm also thinking of adding some midi controlled loops and glitches (maybe pitch or lfo) if someone have good working loops bend point i will be happy to try them if it is still stable with them. (bend point cannot be on the same pint as the midi speak spell devices).