Muff's Modules & More

[giorgio]

looking at the LZX bitvision specs, I see it has an voltage-controlled color phase shifter as well as an envelope follower. It'd be great to be able to patch those out for some CV inputs.

lars, dunno if this kind of info is stuff you'd be comfortable sharing or having people share if we figure it out. let me know if that's the case.

[lizlarsen]

BitVision is meant to very open as far as user community, mods, alternate -software, etc. It's a crude (but effective) generator trying to get the most out of the parts count as possible -- as opposed to the Visionary modules, which use lots of expensive components. The only reason the schematics, code, etc aren't online yet are that they are kind of messy and I need to find time to clean them up!

You could have plenty of fun inserting external voltages into the color phase shifter, but you'd want to be very cautious about voltages too high since it all runs off +5V power. The audio/CV input is protected with a zener diode against over-voltage, so it can already be used with Euro oscillators and so on.

I'll attach a PDF of the schematics for the time being.

[giorgio]

awesome, I'll see if I can dig into this and figure anything out...

[giorgio]

my bitvision is alive as of tonight! it is great, and before I get into any hardware mods, I am gonna learn it fully, and get my own images onto it.

the left LED just seems to be blinking steadily no matter what the input signal is doing, although the input signal seems to make the image glitch a bit.

what is the trimmer for? i'll look through the docs again, but so far this thing is a lot of fun and trippy

[lizlarsen]

Cool! Yes, read thru the documentation in full. The trimmer is to adjust color phase response (turn it counter-clockwise until you see the palette go black & white, then ease it back to the desired point.) Left LED (with buttons facing you) should only be flashing if the input signal is peaking, so with gain all the way down you shouldn't see it. Make sure "param #2" knob is all the way down to get full response from the audio input (it's like an offset control.)

E-mail when you're ready and have an AVR programmer, and I can send you the code.

[giorgio]

i don't have an AVR programmer yet but I'll pick one up, you think the SparkFun Pocket AVR Programmer would work?

http://www.sparkfun.com/products/9231

http://www.hvwtech.com/products_view.asp?ProductID=1098&utm_source=Goo gle&utm_medium=Product+Search&utm_campaign=Product+Search+(Jan11)

i'm gonna go read up on what AVR even is

[lizlarsen]

That's the programmer I use, works great! You'll need AVR Studio (from Atmel's site, you have to register) and WinAVR downloaded and installed.

I have a script right now written in Adobe Flash that takes an input image (jpg, bmp, etc) and basically quantizes it to 16 brightness levels and spits out the image "code". You can copy/paste this code into the project code in AVR Studio, over one of the existing images, and recompile. That's the basic process. There's a LOT of potential for alternative applications for this little board. Anyway, shoot me an e-mail when you're ready and I can send everything over.

[andrewF]

Is it a major task to mod the bitvision for PAL?
or are plans for PAL version still being hatched?

[lizlarsen]

The only changes are using a different part for the crystal and changing some code on our end. Do you have an AVR programmer? If so, you can update any code changes yourself.

All the units Switched On has in stock are built/preprogrammed for NTSC. E-mail me at lars@lzxindustries.net and we may be able to arrange the direct sale of a PAL version kit. It's been something I've been needing to do anyway!

[andrewF]

Thanks - email sent

[snufkin]

oh +1 for pal

[Veqtor]

+1 for pal too!

[lizlarsen]

I've got PAL crystals coming in this week and will have this sorted for you guys very soon.

[andrewF]

drew up a simple circuit to give CV inputs to replace param 1&2 knobs.
EDIT - have built the CV input circuit, the input resistors need to be adjusted as suits the builders system

Find the latest version on my homepage
http://www.sdiy.org/pinky/vid/vid.html

Its basically a two stage mixer, but the second stage attenuates the input and can be setup so the output should be 0-5V.
If i trusted my design chops fully it probably doesn't need the 5v1 zener and diode on the output.

I want to learn more about the
'cycle current counter action'
'cycle current display mode'
'cycle current palette'
functions that are obtained by holding one button and pressing another.
I would like to develop gate/trigger circuits to drive these. Does there need to be a delay between closing the 'hold' button with a gate signal and triggering the other button? Or can they just get a trigger/gate at the same instant?

thanks Lars for all your help with this device

[lizlarsen]

Hey Andrew, yeah that schematic looks good to me!

On the trigger/gate signals and the CV input ("param" knobs, etc):

All of this can easily be changed to work however you want in the software. It's all written in C, and is pretty straightforward what is doing what (hopefully moreso, when I comment and clean it up a bit better.) The only real limitation is the number of input pins on the AVR.

A note on the CV input ("param" knobs, etc.):

In the current application, these are sampled once per frame. So 30 times/second (or 25 times/second for PAL.) So they're not sampled fast enough to do actually visualize the input CV, so best used for low frequency modulation.

The envelope follower output, however, is sampled at line rate -- or ~15.75 KHz. This allows you to actually visualize the waveform. It's quantized by how many bits are in the image, so its a little crude. One useful modification might be a switch to select AC or DC coupling with the envelope follower's input if you want to run CV in here.

On the 3 buttons:

Once per frame, the current state of all of these inputs is read. It looks back one frame to see if you're still holding down a button from the previous frame. If you pressed down all 3 buttons at -exactly- the same time (all gates are high simultaneously), it would be the same as if you had pressed them separately at different times. So there has to be a one frame delay between one gate going high, and the other going high.

My suggestion is that you just do some generic logic inputs + pushbuttons (similar to how you've drawn up a CV input + bias), and then modify the code to get them to do what you want.

If you want to get a video clock signal, in order to clock sequencers off a division of the line rate (or try to sync your oscillators), you could patch out Pin 16 of the AVR (going to pin 6 of the HC4053.) Pins 18 and 19 currently just drive LEDs (for peak detect and frame counter pulses) but those would also be potentially useful patched out logic inputs as well! (Frame counter output with frame counter at max speed, fully CCW, would be a frame rate clock.)

[lizlarsen]

So a summary for "patching it out" experimentation:

Replace Param #1 & #2 pots with CV inputs + bias (as per your schematic)
Replace all three buttons with Logic inputs + gate pushbuttons (or just OR the logic input with the output of the current switch+debounce circuit.)
Patch out pin 16, 18, 19 as logic outputs
Add toggle to bypass C41 (ac-coupling on audio input)

Other note:
For the audio input/envelope follower circuit, if you've got external envelope follower(s) you'd rather use, just replace this whole thing with another CV input + bias like you've got already. Having a bias control here basically makes the "Param #2" knob's function redundant, which means you can use that whole ADC channel to do something else by modifying the software.

P.S. Got PAL crystals in the mail today.

[andrewF]

cheers Lars
Definitely a clock out signal would be useful too.

just ordered my pocketAVR programmer, better dig out my old nemesis; the 'C' programming textbook

[Brownian Lotion]

Can I be a +1 for a PAL version?

I live in Australia and have a friend who needs kickstarting in video..

[lizlarsen]

Sure, no problem. I'll send a note to everyone on this thread that's mentioned it as soon as I have them ready.

[sealion]

Kit assembled last night here on Vancouver island Canada, direct from Austin. First test was running a Casio sk-1 through it and then a Suonio.