Windows 7 (64Bit) Parallels VM on Macbook Pro running BigSur. Arduino version 1.18.19, Digispark ATtiny85 Micro USB.

Loaded Boards Manager http://digistump.com/package_digistump_index.json and updated all. Installed Windows Driver DPinst64 from digistump. Device Manager shows:

libusb-win32 USB Devices
Digispark Bootloader

This a first-time use of Digispark.

I have written a couple of successful programs for the ESP32 devkit v1.

Test Program

    void setup() {                
      // initialize the digital pin as an output.
      pinMode(0, OUTPUT); //LED on Model B
      pinMode(1, OUTPUT); //LED on Model A   
    // the loop routine runs over and over again forever:
    void loop() {
      digitalWrite(0, HIGH); // turn the LED on (HIGH is the voltage level)
      digitalWrite(1, HIGH);
      delay(5000); // wait for a second
      digitalWrite(0, LOW); // turn the LED off by making the voltage LOW
      digitalWrite(1, LOW); 
      delay(5000); // wait for a second

Compiles OK. Upload immediately goes to the following error: (with the Digispark not plugged in).

Running Digispark Uploader...
Plug in device now... (will timeout in 60 seconds)
Assertion failed: res >= 4, file library/micronucleus_lib.c, line 100

I can find no relevant information on the error, I need help.

  • Welcome to SE/Arduino! Please take the tour to learn how this site works. You might want to read some of the pages of the help center, too, while you wait for an answer. -- Granted, my experiences with Digisparks on Windows 10 and Linux are limited. But this error, especially since it appears immediately, points to a problem between the VM and one of the drivers, not the Digispark. Did you consider to use native drivers? -- Please edit your question to add new information, this is not a forum. Commented Nov 30, 2023 at 7:36

1 Answer 1


The device is only in bootload mode for a brief moment after power-up, therefore you have to unplug the device before hitting upload, and only connect it once it tells you to. This way the programmer can hit the bootloader in time to halt normal bootup, before execution is handed off to your code.

Literally stumbled over the same issue today, dunno why it won't just tell you this in the console right away.

  • 1
    This "brief" moment is about 5 seconds long, IIRC. ;-) Commented Dec 2, 2023 at 12:24
  • 2
    However, since the OP did not connect the Digispark at all, this does not answer the question. The posted error appeared immediately. Commented Dec 2, 2023 at 12:25

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