Monday, October 17, 2011

Cube Project Work

This last week has been overall an interesting week. It started off early on dealing with the bending guide prints. I originally had the bending guide print out at 10 times the size it needed because the export changed my dimensions from millimeters to centimeters. After this save option was found and changed, there were a few more iterations made on the bending guides to refine the size and ensure that the LEDs fit nicely and bend accurately.

After I got the final guide done and the prints, I began to work with the code. I struggled for a day or two with trying to figure why the schematic I had worked out correctly was not operating correctly. I did a lot of digging through the datasheets, and spent a lot of time confused as to why the signals that I thought should be operating at 5V were getting like 3.24 V. I then got an idea, borrowed someone else's chipKIT to confirm the idea, and perused the chipKIT user guides to confirm this idea. It turns out that the chipKIT operates at a 3.3V logic level, and I was expecting a 5V logic level. When providing 5V to Vcc on the TLC5940 PWM drivers, the chip then expects 0.8Vcc, or 4V, to be a high signal. Why this worked in the first video and not now I am still unsure about, but when the logic was changed around to 3.3V as opposed to 5V on Vcc, the chip worked again.

The only other problem that I am having right now, probably because of the way I am running the code right now, the LEDs are visibly flashing. It's obvious that right now the software is still too slow, so my next step with the software, after I finalize the schematics over the next few days, is to implement the interrupts and times so that data is bit banged out and the PWM cycles as fast as I think it can. 

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