Atto84 Hookup Guide

Contributors: Nick Poole
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Installing USB Drivers

The Atto84 is emulating USB 1.1 using two of its pins and the V-USB driver. However, there are no common operating system drivers available that work with this custom USB class. As a result, we will need to install custom drivers in order to communicate with (and send our Arduino programs to) the Atto84. Choose your operating system below and follow the directions to install the driver.

Note: We did not write the USB firmware nor the driver. We simply packaged and modified them to work with the Atto84. The true geniuses are the fine folks who wrote micronucleus and libusb.


Insert a micro-USB cable into the Atto84. Your PC will probably make a happy "USB connected!" chime and then inform you that there is an unknown device connected.

Download the SparkFun ATtiny USB drivers by clicking on the link below.

Unzip the file. Open the Windows Device Manager, and you should see an Unknown device. Right-click on Unknown device and select Update Driver Software.

Screeshot of the Device Manager window showing the right-click menu for a device called "unknown device". The "Update Driver Software..." option is highlighted.

In the pop-up window, click Browse my computer for driver software.

Screenshot of the "Update Driver Software" interface. The option labeled "Browse my computer for driver software" is highlighted.

Click Browse... and open the folder that contains the drivers you just unzipped. It will likely be the sparkfun_attiny_usb_driver folder.

Screenshot of the "Browse for driver software on your computer" interface. In the field labeled "Search for driver software in this location:" I've typed the filepath to my sparkfun_attiny_usb_driver folder.

Click Next. You may get a warning pop-up that says "Windows can't verify the publisher of this driver software." That's OK. Just click Install the driver software anyway.

Windows Security prompt warning the user that the driver is unsigned. The "Install this driver software anyway" option is highlighted.

You should see a notification that the SparkFun ATtiny driver was installed successfully. Close that window, and verify that your Unknown device now shows up as SparkFun ATtiny in the Device Manager.

Screenshot of the Device Manager window again, this time showing a device enumerating under "libusb-win32 devices" as "SparkFun ATtiny"

Mac OS

You'll need to install Homebrew and use it to install libusb. Enter the following commands into a Terminal:

/usr/bin/ruby -e "$(curl -fsSL"
brew doctor
brew install libusb-compat


Good news! Linux doesn't require special drivers. However, you will need to do one of the following to be able to program the Atto84 from Arduino:

1) When you download the Arduino IDE (next section), make sure you run it as root: sudo ./arduino

Very exciting screenshot of a terminal with "sudo ./arduino" typed in

2) Or, you can add some udev rules so that Linux enumerates your device with write permissions. Create a file in rules.d:

sudo edit /etc/udev/rules.d/49-micronucleus.rules

Copy the following contents into that file:

# UDEV Rules for Micronucleus boards including the Digispark.
# This file must be placed at:
# /etc/udev/rules.d/49-micronucleus.rules    (preferred location)
#   or
# /lib/udev/rules.d/49-micronucleus.rules    (req'd on some broken systems)
# After this file is copied, physically unplug and reconnect the board.
SUBSYSTEMS=="usb", ATTRS{idVendor}=="16d0", ATTRS{idProduct}=="0753", MODE:="0666"
KERNEL=="ttyACM*", ATTRS{idVendor}=="16d0", ATTRS{idProduct}=="0753", MODE:="0666", ENV{ID_MM_DEVICE_IGNORE}="1"
# If you share your linux system with other users, or just don't like the
# idea of write permission for everybody, you can replace MODE:="0666" with
# OWNER:="yourusername" to create the device owned by you, or with
# GROUP:="somegroupname" and mange access using standard unix groups.

Save and exit.