jaycerochester wrote:Workinonit wrote:I managed to get up to 40 arches working but the whole system is locking up very frequently at that distance. But this is why we did it 2 weeks before we have to leave. You do full set up to find the problems here and not on the playa. Several ideas have been thrown around and we ARE going to fix it!
I spent the better part of a couple days on what turned out to be a rather silly problem. I just felt the need to hijack your thread to vent!
I'm using a PIC microcontroller to drive a chain of LED drivers (PCA9922, shift-register-style drivers with 1-resistor current setting). I started using the PIC's synchronous serial port feature for the first time to shift the data out, and I was getting bizarre results. I surmised a clock problem, but couldn't really decipher it as it was spurious and weirdly effected by oscilloscope probes. I barked up the wrong tree for a bit concerning the duty-cycle (which, on the PCA9922 spec sheet expects 40% to 60% although it can handle "0 to 25MHz".) Nonetheless, I finally determined that it must have been some RF noise as a capacitor rounded off the clocks enough to work perfectly. Well, sort-of ... it _works_ at least.
The project is a sick bit of elegance that should let me drive 50 (or more) RGB LED's (150 emitters) with 8-bit pulse-width modulated (PWM) resolution from a 20MHz-clocked PIC. And then do animation and processing on the side. I'm using a technique called bit-modulation for PWM which disassembles all the PWM values into bits, sets the shift registers to turn on all LED's with bit 7 set, sets all the output-enable pins for 128 cycles, then moves to bit 6 for 64 cycles, bit 5 for 32, and so-on. The effect is that over the course of 256 cycles, each LED is on for its PWM value's duration, except the processor only has to do heavy computing 8 times per those 256 cycles. I cheat a bit and don't get to 100% brightness because of fixed delays between cycles and such, but it's accurate enough.
Workinonit wrote:Have you tried looking at the FastSPI_LED library? That is what I am using, but sounds like you went ahead and customized for your own application.. It does bit banging to do the PWM. However, the LED strips I am using do their own PWM so it takes all the processing off the driving processor. Look for LEDs with the TM1801 or WS2801 pixel controlers... Also recently heard about the Wixel, new controller chip... have not had time to check it out but sounds like a promising bit of technology for this type of stuff.
Workinonit wrote:You can look at this doc http://www.nxp.com/documents/data_sheet/P82B96.pdf for some help with you capacitance issues.
Workinonit wrote:Good luck sir!
MyDearFriend wrote:Oh man (((Workinonit))) that is so AWESOME I am so impressed and so excited to see this!!!
Savannah wrote:It sounds freaky & wrong, so you need to do it.
Workinonit wrote:Holy crap! I did it!
Foxfur wrote:CFM, Mr. Five, and I rode out to the ToQE on Saturday night before opening. I walked up to a gentleman who was at work soldering and asked him if he was on eplaya. He said yes, his name was Workinonit! I asked him if he'd ever heard of Foxfur. He screwed up his face, thought about it, and said he'd never heard of him, Bwahahaha! I told him Ff's a pretty cool guy but a bit of a spaz and then introduced myself as CFM!
What a fuckin blast.
I enjoyed the hell out of the tunnel. Very well done! Thank you!
FIGJAM wrote:Are you taking it to AZDC?
ibdave wrote:Hey Hey Hey,
Great Project and many thanks..
I chatted with ya for a brief moment as you were doing a repair in the dark and I held my light for ya..
(you weren't happy, mutterings about fucking not respecting art)(your so right)
I told ya about me helping Mark Lottor out and you perked up and really hopped to meet him.. Did ya?
I still have his email if you need it.. send me a PM.... Great Project and can't wait to see what you create next...
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