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drivers for Gemmas connecting to a PC ...

Getting the Windows driver for Gemma

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a. Download the Windows driver. Go to:


The page is called, 'About the Bootloader' - a bootloader is the software which handles what happens when Gemma is powered up, and how it receives new code. You will find the page useful later when you come to upload code yourself.

Read on down and there is a section 'Gemma USB Drivers for Windows'.

Find where it says "just click here to download the ZIP", and do it. You should now have a file called something like usbtinyisp_w32_driver_v1.12.zip

b. Unzip the driver. Unzip this to a known place. You should now have a folder called usbtinyisp.

We have a separate page for actually installing the driver, but do read on first

READ THIS. In a perfect world, all drivers for Windows would be 'signed'. that is, they would be securely identified to say who wrote them. The standard driver for Gemma above is not signed (which is not unusual). This can give problems on later versions of Windows which more strictly enforce the need to be signed (a not inexpensive process).

Luckily someone seems to have sorted the problem (see below). On our page of successful installations of installing Gemma using Windows drivers, one of the example systems worked with the driver below.

If you still have problems, then view the following Adafruit page for more on Windows Gemma driver problems and solutions and remember that Adafruit have a very useful webforum.


Important: Windows 7 and 64 bit driver.

Browse to the following post in this adafruit forum: "I think there is an updated driver available (Win 7 and 64 bit)"


Go down to the Sept 22 2008 post (thanks to 'mightyown') and download the zip file. This gives suitable drivers for Win7 and 64 bit systems, which Windows will not throw out as unsigned (apparently "since a Microsoft KMCS accepted digital signature is embedded in the kernel driver libusb0.sys"). That is all a bit too techie for us, but it seems to work.

Adafruit have pinned this post at the top of their USBtiny forum, so assume they must rate it.