If you have a dedicated AVR programmer, go right ahead and use that to upload micronucleus-t85/firmware/releases/micronucleus-1.05.hex, then set the fuses to: lfuse = 0xF1, hfuse = 0x5F, efuse: 0xFE
If the above doesn't mean anything to you, follow the
littlewire tutorial to install the littlewire programmer software in to one of your digisparks. Next, install avrdude on your computer somehow. For Mac's, install the latest version of
CrossPack. Download this
https://github.com/Bluebie/micronucleus-t85 (the ZIP button) and open a command line or terminal.
In the terminal type "avrdude -c usbtiny -p t85 -U flash:w:" then drag in the micronucleus-1.05.hex file from firmware/releases in the zip you downloaded.
Next, get your attiny85 chip and stick it down on a breadboard. Use jumpers to connect it to your digispark, connecting every pin for pin. Looking at the chip with the little indented circle in the top left, the pins start at bottom right with D0 and then go up that side D1 and D2 - connect all of these with wires, and connect the top right pin to 5v. On the left side connect the bottom left pin to gnd, and the top right pin goes to D5.
Now go back in to your terminal and press enter on that command we setup before. avrdude will talk over USB to the littlewire software, which will translate commands across to upload the micronucleus firmware in to the chip.
Once avrdude has finished uploading and verifying micronucleus on the chip we need to change the fuses. To do this, enter the following command: "avrdude -c usbtiny -p t85 -U lfuse:w:0xf1:m -U efuse:w:0xfe:m -U hfuse:w:0x5f:m". After this command you will no longer be able to use your ISP programmer on this chip- the reset pin has been disabled so you can use it as IO (it is D5).
Next, you'll need to wire up a USB connector to your chip in the usual way with resistors and zenner diodes. If you search the web for 'V-USB' you can find heaps of examples. The chip we're using needs to be wired up like the digispark - two zenner diodes, three resistors, connecting the D3 and D4 pins to the USB data wires. You can see a simplified schematic for this sort of setup on the
littlewire.cc download page. Note that the particular resistor values aren't very strict. Many USB projects use 68 ohm resistors where the littlewire uses 27 ohm, and the 1.2kohm in the littlewire circuit is usually 1.5kohm. Try using whatever resistors you can which are close to those values. The zener diodes are much stricter. Get the lowest wattage zener diodes you can.
These ones are known to work well. If you can't wait, try the circuit without zeners - some computers will put up with it, some wont!
I recommend against running the tiny85 chip at less than 4v (which is sometimes a hack used to do without the zener diodes) because once when I was running a chip at 3v it became bricked, and I had to replace it. Maybe you'll be luckier, and maybe 3.6v isn't so bad, but I still dislike this method as it runs the chip totally out of spec.
Anyhow, once you've done all that stuff you should be able to upload sketches to your chip from the digispark arduino software just like the real thing!
