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LED pictures in the sky

LitterBug

Troll Spammer
#3
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LitterBug

Troll Spammer
#4
Picked up a 1meter 60 pixel DotStar strip for half price. Should be plenty enough to do a proof of concept before $pending more on the high den$ity 144 pixel $trip.

Cheers!
LitterBug
 
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LitterBug

Troll Spammer
#5
Picked up a 1meter 60 pixel DotStar strip for half price. Should be plenty enough to do a proof of concept before $pending more on the high den$ity 144 pixel $trip.

Cheers!
LitterBug
Egads, The better looking of the two examples that I was using to do the build was done in 2012 on an original Raspberry Pi. LOL Let's just say a few things have changed since then including the GPIO pinouts, the Libray Name, etc.... Have a good start on the build. Currently using a 3A BEC, and will probably switch to a 5 or 6A bec since 3A is not enough to drive all the LEDs at full power at the same time.

Cheers!
LitterBug

EDIT: The old library has actually been depricated. The new CircuitPython DotStar libraries can be found here: https://github.com/adafruit/Adafruit_CircuitPython_DotStar
https://pypi.org/project/adafruit-circuitpython-dotstar/

These require the Python3 libraries to be installed.
sudo apt install python3-picamera​
sudo apt-get install git usbmount python-dev python3-pip libopenjp2-7 libtiff5​
sudo pip3 install adafruit-circuitpython-dotstar​
sudo pip3 install evdev pillow adafruit-circuitpython-dotstar​
other tutorials​
 
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LitterBug

Troll Spammer
#8
Finding the POV refresh speed is not as fast as I would like. I'm sure some of it is the adafruit libraries are using Python rather than C. The Pi 3 B+ is OK for a 60 pixel strip, but if I were to jump up to 144, it would be rather sluggish. Going to try to get it all running on an Asus TinkerBoard running Armbian. The Tinker Board clock (1.8Ghz) is higher than the PI 3 (1.4Ghz), and faster than the latest Pi4 (1.5Ghz). I flipped my SD card over to one of the original Pi1 B+ boards (700Mhz), and was surprized at just how slow it ran there. Especially since most of these old guides were written back when that was king. The Pi B+ seemed way slower than 1/2. At any rate, I have also started digging in to the protocol used by the dotstar LEDS in case I need to start writing my own stuff. I would like to set it up running C for comparison to Python.
1604775405617.png


Cheers!
LitterBug

Edit: Well drat. gotta fix the adafruit libraries to use them on the Tinker Board:
Code:
NotImplementedError: Board not supported ('ASUS_TINKER_BOARD',)
 
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LitterBug

Troll Spammer
#9
Hmmm. Part of the problem with the slowness on the Pi1 B+ is the SPI bus does not want to run > 2Mhz. that's about 1/10 the throughput I get with the Pi3 @ 20Mhz. The Pi1 B+ still be a good box for doing light painting, but not for high refresh rate POV. Have played with the SPI clock on the PI3. Not sure if going much over 20Mhz is worth testing, since my max scope sample rate is only 40MsPs. The DotStar LEDs are known for having issues at clock rates > 24Mhz on longer strands. Suppose I can try to bump up to 32Mhz. Will have to find a different tool to measure the clock to verify that it is actually running at the higher speeds. May try using one of my RTL_SDR dongles and SDR# to see if they pick it up. Should be able to.

Cheers!
LitterBug
 

LitterBug

Troll Spammer
#10
Have an Arduino or two laying around so figured I might as well give it a go there too. Pin headers I used work perfect with both rPi and Ard.

Going to work on a 3D printed holder/diffuser. Square black holes with drop in clear diffuser blocks. Should give it a more pixely look rather than the narrow streaks when painting/pov. Make it less dottie! ;)

Adafruit Metro Mini Arduino running Adafruit DotStar library demo
Adafruit 60 pixel DotStar strip connected VIA SPI bus
ReadymadeRC 5V 5A UBEC to power it all and make it easy to power via various power sources.

There are some newer Arduinos that are clocked at 64 Mhz. Will have to see if the SPI bus will scale to 32Mhz or higher. The Uno/mini is only clocked at 16 Mhz, and the SPI bus is limited to 8mhz (1/2 clock)

Cheers!
LitterBug
 
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LitterBug

Troll Spammer
#11
Playing with another Arduino library called FastLED that is WAY more robust and easier to set up than the "old" Adafruit libraries. It allows for a much wider variety of LED strips, boards, and has capabilities for doing multiple outputs at the same time. Could plausibly set up a scrolling message board like the GY Blimp....

Now to figure out how to do POV with it....

Cheers!
LitterBug