Re-program Digispark Fuses in Circuit with HVSP

How to use an Arduino based high voltage fuse programmer on Digispark without having to modify the board, remove parts etc.

If you are trying to re-program the fuses on the Digispark ATTINY85 using an ISP programmer but you mess up the fuses, you can use a high voltage programmer directly on the module to re-gain functionality of the device.

Note: The rise time for VCC on the scope trace at around 7:30 in does look like it may rise high enough within 20 µs as required, but sometimes it takes longer so adding a 100 µs delay made it more reliable. Scope traces were added to Github showing VCC rise time of ATTiny85 alone (fast) vs powering the Digispark board (gradual ramp).

Sketch/Schematic: https://github.com/GadgetReboot/Arduino/tree/master/Uno/AVR_High_Voltage_Fuse_Programmer

Original video detailing the high voltage programmer used in this adaptation: https://youtu.be/JskwC4bhgx4

Direct Project References: Ralph Bacon's version of the Arduino DIY project: https://github.com/RalphBacon/ATTiny85_Fuse_Resetter

https://arduinodiy.wordpress.com/2015/05/16/high-voltage-programmingunbricking-for-attiny/

Useful Tools: AVR Fuse Config Calculator http://www.engbedded.com/fusecalc/

Online schematic drawing for quick circuits: https://www.circuitlab.com/editor/#

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