fastspi not able driving more then 350 times WS2801?

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hardtoneselector

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Hello,

I created a Matrix with 32x18 (500/576total LEDs) WS2801 LEDStrings (Chinese Manfacturer). Using bitbanging method (based on firmware from http://www.solderlab.de/index.php/software/glediator) everything is fine but reach only less then 15fps.
When I try to use the fastspi solutions (http://code.google.com/p/fastspi/), it appears that clock and data becomes out of sync, the LEDs seems to be missing clock signals.
Please watch the videos taken:
@24MHz: http://www.youtube.com/watch?v=-vjy4Jtzj7I
@48MHz: http://www.youtube.com/watch?v=QREboDgavxs
@96MHz: http://www.youtube.com/watch?v=XlgE8365qwA

FastSPI_LED.setDataRate(0..7); makes a differnce but not found any combination it worked fine all the LEDs.

When I interpretate it right, WS2801 will refresh the data signal in each LED but Clock is wired to all LEDs paralell,...
I don't have a scope available, so I cant tell is it a voltage drop or a timing issues.
What do you think?
Does somebody sees a solution or a test I could try?

greetings
Bernie

PS: my first own µcontroller Project :)
 
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I have definitely run into problems with driving the ws2801s at long lengths and high speeds. I suspect that the bitbanging that you are doing is still than even the slowest hardware SPI - which is why that is working for you.

I'm working on a refresh of the library that has more efficient bitbanging code, and is also a lot more flexible - so what you could do is split your leds into multiple chains, each with their own set of clock/data pins. By making each chain shorter, you could up the speed that you can update on. I'm still a couple weeks out from having a release, but the new core code is most definitely up and running. I can max out the hardware SPI at about 5.8Mbps data transfer rate - and I've been able to push 3.1Mbps with bit banging!

(Also the new library is smaller and more flexible!)
 
That BingBanging is slow(enough) was also my thought.
I would prefer a faster method since I only reach up to 18fps with the bitbanging method used. I got the teensy3.0 to use the hardware spi support,....

Nice to hear that you are working on a new version of the fastspi lib, but improving the bitbangig method in the library would not help me, or? WS2801 support in the library is hardware spi, or do i have a mistake here?
I thought about about splitting in more chains, but don't like the idea of changing the wiring at this point.
I will give the lib a try, when it is available.
Thank you for your reply! :)

bernhard
 
The new library will support both hardware and software SPI - and you will be able to fine tune the speed of the software SPI so you can adjust it until you stop seeing glitching.
 
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