So having used the same circuit a dozen times to run WS2811s I designed and sent off for a PCB to be manufactured.
It doesn't work. I'm baffled.
I wasted an hour tonight trying to program the ATTiny with a USBAsp, but when I fell back to using the Arduino as ISP again, bingo, it programmed fine. Then I wasted an hour because I forgot that while the ATTiny85 doesn't have a bootloader you still have to use the "Upload bootloader" to set the clock bits to 16Mhz. It was only when I used "blink" and found my 1 second delay was a lot more like a 16 second delay that it twigged.
However, with the clock now running at 16Mhz and the data line going to the LEDs showing an appropriately fast slightly shifting square wave with the pauses in the right place (I didn't write the base frequency down)...
It still doesn't work.
There are three things different about this circuit.
1. I used an actual PCB.
2. I used a SOIC-8 ATTiny.
3. This circuit has a pull up on pin 3 (arduino pin 4)
The rest is the same, including the code. The FastLED demo reel.
The only lead I have is that the fall time on the square wave is far too soft it drops fast initially but then softens out into a curve. However I have never probed the breadboard or protoboard LED controllers as they just worked.
Is this likely to be some form of track capacitance issue? Is there anyway to help cure it, or even confirm it?
Capture of the board is here:
The only revision to this board since is reversing the +12V and GND as they were backwards for the DC jack foot print. So in fact the data line is running under the GND not the 12V rail in the current PCB.