RGB POV Globe, 64 RGB LEDs

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funvill
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Joined: Fri Mar 18, 2011 9:37 pm

RGB POV Globe, 64 RGB LEDs

Postby funvill » Fri Mar 18, 2011 9:50 pm

Hello

I am planning on creating a RGB LED POV globe only physically larger then that one. I am planning on using 64 RGB LEDs, requiring 3x pins per LED for a total of 192 outputs.

It has been suggest that I look in to the xcore line of products for my micro-controler.
http://electronics.stackexchange.com/qu ... -questions
http://electronics.stackexchange.com/qu ... ts-of-pwms

I'm looking at the XC-3 LED Tile Control Kit
http://www.xmos.com/products/developmen ... d-tile-kit

What I don't understand is how do I go from this board to the 192 pins on on the LEDs.

My questions are:
* Can you point me towards a tutorial on the subject?
* Is this board appropriate for this project, if not can you make a suggestion on what that would be?

Thank you for your time.
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paul
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Joined: Fri Jan 08, 2010 12:13 am

Postby paul » Fri Mar 18, 2011 10:20 pm

Hi Funvil - and welcome to XCore!

You need to come up with more efficient way to wire up the LEDs - typically they are usually wired up in rows in a matrix (like this - http://hackedgadgets.com/2007/01/29/led ... formation/). This then reduces the LEDs I/O requirements.

For your POV you can put the 'rows' next to each other to essentially group the LEDs.

Then you need to work out how you want to get your data to the unit. If using ethernet, you probably want to look at the XC-2. The XC-3 is quite specifically designed for certiain LED controllers (though if you are using them you may well be able to make use of the XC-3).

Hope that points you in the right direction!
Paul

On two occasions I have been asked, 'Pray, Mr. Babbage, if you put into the machine wrong figures, will the right answers come out?' I am not able rightly to apprehend the kind of confusion of ideas that could provoke such a question.
funvill
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Joined: Fri Mar 18, 2011 9:37 pm

Postby funvill » Fri Mar 18, 2011 10:54 pm

Then you need to work out how you want to get your data to the unit.
I was planning on generating the images internally based on an algorithmic (hard coded)
You need to come up with more efficient way to wire up the LEDs
OK, say that I made a matrix of LEDs, where do I physically attached them to the board?

With the prototype that i made with an Arduino I would attach them to the PWM pins and use a shift register to output to 32 LEDs from three 3 pins.
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paul
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Postby paul » Sat Mar 19, 2011 12:30 am

funvill wrote: I was planning on generating the images internally based on an algorithmic (hard coded)
I would recommend the XC-1A then - unless you ever want to get some ethernet connectivity.
funvill wrote: OK, say that I made a matrix of LEDs, where do I physically attached them to the board?

With the prototype that i made with an Arduino I would attach them to the PWM pins and use a shift register to output to 32 LEDs from three 3 pins.
XMOS devices have general purpose ports - so there is no concept of 'PWM pins' etc. However the ports are quite advanced and have buffers (shift registers) that can clock data out of the port at a user defined rate. They also have integrated timers and other features that make them incredibly flexible.

I would recommend taking a look at the Programming XC on XMOS Devices document which will give you a good grasp of the port features and how to begin using them.

If you want to play around with getting PWM out of the device then a good start is to download the XMOS tools (it costs you nothing!) and start running things in the simulator. This allows you to simulate the waveforms coming out of the device and so you see how the pins behave (and thus fine tune your PWM).

I would also recommend you take a look at the open source PWM component available here - https://github.com/xcore/sc_pwm

I haven't looked/tried to see if it is suitable for what you are doing, but it might be a good starting point...
Paul

On two occasions I have been asked, 'Pray, Mr. Babbage, if you put into the machine wrong figures, will the right answers come out?' I am not able rightly to apprehend the kind of confusion of ideas that could provoke such a question.
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evertech
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Joined: Tue Mar 22, 2011 7:50 pm

Postby evertech » Tue Mar 22, 2011 8:00 pm

You need to first determine the motor drive which will set you rpm. You then need to determine how many
"frames per second" this display needs. That will determine how many rows of LEDs you will have to
mount. Next, to change the LED outputs you have to determine parallel or serial for the LED drivers.
Are you going to use 8, 16 or 32 bit microcontroller? Many hobbyists are using the arduino system.
I prefer assembly language and 100 MIPs 8 bit.

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