Nutcracker --> Arduino?

**Jonpro03** · 04-25-2012, 10:20 PM

No, I don't need the string number. Just the value bytes in a certain order and I'll figure out what data goes where.

Say I've got 12 channels.
The first event for a spiral is to have channel 1, 2, and 3 on and all of the others off. The first string will look like this

88 AA FF 00 00 00 00 00 00 00 00 00

The second event has 4, 5, and 6 on and all others off

00 00 00 88 AA FF 00 00 00 00 00 00

It may also be worth while to have the sequence length (2000 milliseconds), event period (50 milliseconds) and number of channels in the file. That way it does not need to be entered manually. ASCII characters are ok, maybe separated by spaces.
So the beginning of this file would look like this:

2000 50 12 88 AA FF 00 00 00 00 00 00 00 00 00 00 00 00 88 AA FF 00 00 00 00 00 00 ....

**DennyMo** · 04-26-2012, 09:51 AM

Originally Posted by Jonpro03

Say I've got 12 channels.

Are you talking about "12 pixels" or "12 strings of 'dumb' RGB lights"? If you're talking about twelve pixels, then I don't think your suggested format is very scalable. If I'm working with 100 or 1000 pixels, that becomes one huge line of code/data. Is that manageable?

Or am I not thinking enough like a microprocessor?

**Jonpro03** · 04-26-2012, 11:02 AM

I am worried about the capability of the processor. I realize that a realistic channel count is way over 1000. With an event period of 50 milliseconds, the Arduino will be expected to read in 1KB+ of data and move it out within that time period.
Perhaps it may be beneficial to address the bytes so we can prevent the Arduino from reading in a bunch of off channels, and just have it assume that all channels are off unless a byte is addressed to that location. It would decrease file size and read times.

I need to read into the pixel library a bit to find out what exactly is needed from the Arduino.

What library does everyone use?

Is it the Ladyada one or the GE one?

Or should I plan on both haha!

**smeighan** · 04-26-2012, 12:17 PM

Originally Posted by Jonpro03

I am worried about the capability of the processor. I realize that a realistic channel count is way over 1000. With an event period of 50 milliseconds, the Arduino will be expected to read in 1KB+ of data and move it out within that time period.
Perhaps it may be beneficial to address the bytes so we can prevent the Arduino from reading in a bunch of off channels, and just have it assume that all channels are off unless a byte is addressed to that location. It would decrease file size and read times.

I need to read into the pixel library a bit to find out what exactly is needed from the Arduino.

What library does everyone use?

Is it the Ladyada one or the GE one?

Or should I plan on both haha!

Before i produce a file maybe that concept should be proven.

A 3 minute song using a 50ms frame rate on a mdeium sized tree (16x50)
180 secs x 20 frames/sec * (16x50) pixels * 3 channels per pixel = 8.6mbytes of binary data = 48kbytes/sec

a larger tree (48x64) , which one nutcracker user has, = 33.2mbytes for the 3 minute song = 184K/sec

Does the arduino support a sd card? I was thinking we could load teh card from a pc and then plug it in after it has a show.

It seems to be scalable for the future, you would have something like this
for each frame
for each string
for each pixel
output r,g,b

somewhere in here you will span dmx universes

**Jonpro03** · 04-26-2012, 02:32 PM

There's a reply in this thread http://arduino.cc/forum/index.php?topic=66241.0 in which the author of the SD library says that we can expect read time's of 250KB/sec on an Arduino. So we know that the limiting factor will not be the read speed of the SD card.

In order to update a single pixel, both the adafruit and the GE strings require the entire string to be updated. I think it may defeat the purpose of addressing bytes.

Thoughts?

**smeighan** · 04-26-2012, 04:54 PM

Originally Posted by Jonpro03

There's a reply in this thread http://arduino.cc/forum/index.php?topic=66241.0 in which the author of the SD library says that we can expect read time's of 250KB/sec on an Arduino. So we know that the limiting factor will not be the read speed of the SD card.

In order to update a single pixel, both the adafruit and the GE strings require the entire string to be updated. I think it may defeat the purpose of addressing bytes.

Thoughts?

maybe for scaling we could divide the pile of data for a song in two and have two arduino's each driving half of the tree. Can two of them be kept in sync to within say 25ms?

**Jonpro03** · 04-26-2012, 08:26 PM

Arduino's can communicate with each other, using I2C I think.

What I'd like to do is get some pixel strings, hard code some channels on the SD, and push the limits to see where we stand. I'd also like to know what everyone is using on their trees/etc...

Sadly, it'll be a while before I can spend some money on blinky/flashy