How to Program Micronucleus Bootloader on ATTiny85 and Digispark

How to program the micronucleus bootloader into an ATTiny85 on Digispark if it requires reprogramming. Arduino as an ISP is used to do the programming and this requires the ATTiny85 reset pin to be fused as a reset pin instead of GPIO. If the reset pin is set as a GPIO, the fuses need to be changed with a high voltage programmer such as the one here: https://youtu.be/Qw54GcPNIf8

Micronucleus bootloader files: https://github.com/micronucleus/micronucleus/tree/master/firmware/releases

Schematics for programming ATTiny85/Digispark https://github.com/GadgetReboot/misc_file_bin/blob/master/2019-03/ATTiny85_Prog_Schematic.jpg https://github.com/GadgetReboot/misc_file_bin/blob/master/2019-03/Digispark_Prog_Schematic.jpg

AVRDude command line to program Micronucleus hex file using Arduino as ISP Change “/folderpath/” to the location of files and “COMPORTNAME” to your programmer’s COM port

/folderpath/avrdude -C /folderpath/avrdude.conf -v -P COMPORTNAME -b 19200 -c avrisp -p attiny85 -Uflash:w:/folderpath/t85_default.hex:i -U lfuse:w:0xe1:m -U hfuse:w:0xdd:m -U efuse:w:0xfe:m

For optional fuse settings to change the reset pin into reset or GPIO functionality, use one or the other “hfuse” parameters in the programming command line:

Digispark fuses with reset pin acting as reset instead of GPIO hfuse:w:0xdd:m

Digispark fuses with reset pin acting as GPIO instead of Reset hfuse:w:0x5d:m

More AVRDude usage info: http://www.ladyada.net/learn/avr/avrdude.html

Install USB drivers for Micronucleus device if needed: https://learn.sparkfun.com/tutorials/how-to-install-an-attiny-bootloader-with-virtual-usb#install-usb-drivers

Use Arduino as an ISP programmer https://youtu.be/7Rz9A9VbDx4

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