The Attiny85 firmware need to disable Reset. If you don't have a high-voltage programmer, you won't be able to program it anymore.

With a bootloader, you don't need a high voltage programmer to update the firmware. However, if your bootloader got damaged or you want to change the fuse, you still need a high voltage programmer.

I used micronucleus bootloader. You can get the hex file from here.

Before programming bootloader, use ISP programmer to set fuses correctly. I used C1 DD FE fuses. Make sure you checked SELFPRGEN.

Then you use the command-line tool in micronucleus's repo to upload the dwire-debug's firmware.

If you do it correctly, everytime you plug in the ATtiny85 board, it will appear as a Vendor-Specific Device with PID:0x0753 & VID:0x16d0. If you don't upload firmware, it will automatically become USBtinySPI with PID:0x0c9f & VID:0x1781 after 6 seconds.

After you confirm your bootloader is working, set fuse RSTDISBL with the ISP programmer.

I did some improvement on dwire-debug and created a release here.

If you are using Mac, you can download binary, add execute permission with chmod +x dwdebug, install libusb with brew install libusb libusb-compat .

If you are using Windows, you need to use libusb-win32 driver for ATtiny85. Refer to Readme of dwire-debug repo for more info.

For other OS, try to compile the source in the release.

Connect all wires and USB cable. run the following command in terminal to read fuse. If the avrdude on your computer locates in a different location, change the path accordingly.

/Users/sundeqing/Library/Arduino15/packages/arduino/tools/avrdude/6.3.0-arduino9/bin/avrdude -C/Users/sundeqing/Library/Arduino15/packages/arduino/tools/avrdude/6.3.0-arduino9/etc/avrdude.conf -patmega328p -cusbtiny

Check if the signature and fuses are read correctly.

If so, program new fuse values to enable debugWIRE and disable bootloader.

/Users/sundeqing/Library/Arduino15/packages/arduino/tools/avrdude/6.3.0-arduino9/bin/avrdude -C/Users/sundeqing/Library/Arduino15/packages/arduino/tools/avrdude/6.3.0-arduino9/etc/avrdude.conf -patmega328p -cusbtiny -U lfuse:w:0xEF:m -U hfuse:w:0x9B:m -U efuse:w:0xFD:m

Power cycle your board to make fuse change take effect.

In terminal, swtich to dwdebug's location and run ./dwdebug device usbtiny1. Check if ATmega328p can be connected. If so, press Control+C to terminate dwdebug.

First download VScode from https://code.visualstudio.com/

Enable extensions side bar.

Look for Arduino extension (the offical one from Microsoft, not a random person) and install it.

Then you install Arduino extension.

Click reload after you finish install.

Step 6, Add support for debugWIRE

Quit Vscode (not close the window)

In Mac, open finder, Click "Go"->"Go to Folder"

Open extension folder (you can copy & paste):

>td ###macOS

Paste path

Then you will arrive extension folder

Go into the Arduino extension folder (vsciot-vscode.vscode-arduino-0.2.22 at this moment) -> "misc", you will find debuggerUsbMapping.json and usbmapping.json file.

Refering to this commit, add support of USBtinySPI and Uno into debuggerUsbMapping.json and usbmapping.json

This repo contains a configured example. In VScode, open folder BlinkUno in this repo.

Change miDebuggerPath and debugServerPath launch.json. Make sure they are pointing to the correct files.

Add breakpoints and you can start debugging the code.

Also tested on windows.

If debug server can not start, it may be caused by exiting debug while code is running. Kill running dwdebug will fix it.

Exit any debugging session.

In terminal, swtich to dwdebug's location and run ./dwdebug device usbtiny1. Type qi to quit debugWIRE

Then program fuse back with /Users/sundeqing/Library/Arduino15/packages/arduino/tools/avrdude/6.3.0-arduino9/bin/avrdude -C/Users/sundeqing/Library/Arduino15/packages/arduino/tools/avrdude/6.3.0-arduino9/etc/avrdude.conf -patmega328p -cusbtiny -U lfuse:w:0xFF:m -U hfuse:w:0xDA:m -U efuse:w:0xFD:m

Then you can burn bootloader back and reuse the board as before.