A link to the pixel display please.
a block diagram of how everything was connected please.
how does the ATTiny85 fit into this?
the 5v regulator used on the Arduino UNO has short-circuit protection.
Also looking at the Arduino UNO Schematic I do not see a path in the 5v regulator circuit to short to ground.
I’m in work, so diagram upload would be difficult. Let me try and explain and ASCII art my way out of this.
High Level it’s a standard Arduino as ISP programmer for the ATTiny85. The ATTiny85 is controlling the 12V LED strip, the UNO is programming the ATTiny85. The UNO gets it’s power from the USB. The ATTiny gets it’s power via a 5V regulator from the 12V LED supply.
USB → Arduino UNO → ISP Programming lead → ATTiny85(MOSI, MISO, SCLK, RST, GND) (pin 3) → WS2811 60 LED 12V Strip
The Arduino UNO is power by the USB 5V.
The LED Driver board is powered from a 12V supply. The ATTiny85 gets power from an LM78L05 regulator.
So the power diagram looks like:
USB-5V → UNO | ISP SPI+GND no power| ATTiny85 ← 5V REG ← 12V → WS2811 LED strip.
No 12V power reaches either UNO or ATTiny85. No power from the UNO or ATTiny85 reaches the LEDs.
I recently discovered the LM78L05 will short to ground if you put a high voltage on it’s Vout than it’s Vin. So for example if you are powering a 5V circuit from 12V via the regulator and attempt to put 5V directly yourself and power off the 12V supply. This shorts the 5V through the regulator to ground. The regulator gets very hot.
What I believe has happened here is that one of the SPI pins has been high/5V. When I powered off the 12V supply that 5V has found a route through the ATTiny85 to it’s Vcc pin. That has then routed to GND via the LS78L05 and the USB CH340 IC in the UNO has taken a beating.
The visible sumptons were that when I powered off the 12V supply the UNO’s lights dimmed and went out. I confirmed it was not being powered by the 12V side by removing the USB lead. The UNO powered off. This leads me to conclude that the voltage regulator shorted it out.