Datasheet

Using the USB Bootloader

About the bootloader

bootloader

is a tiny piece of software residing on the microcontroller that that helps load your own code into the

remaining space.

One of the challenges with the Pro Trinket is that we wanted to have a built-in USB bootloader, but the ATmega328

doesn't have built-in USB hardware!

So instead, Frank (our awesome engineer with mad USB chops) created a USB bootloader that combines the

elegance of V-USB with the well-supported and tested nature of the USBtinyISP. This bootloader looks just like a

USBtinyISP - and since it uses the unique Adafruit VID/PID we own and that we added to avrdude so long ago, it works

with only very minimal configuraton tweaks. No need to recompile anything, whew!

Then, since we had a little space left in the bootloader area of the chip, we added Optiboot support. You can use

either

the USB connector

an FTDI cable so that it acts just like an Arduino Uno for programming, for max flexibility.

The Pro Trinket is smart enough to auto-detect which bootloader you are trying to use. If you plug the USB port in, it

will enumerate as a USBtinyISP for USB bootloader. If you plug in FTDI and use the Arduino Uno programming

procedure it will use that technique

Pro Trinket USB Drivers for Windows

The cool thing about the bootloader on the Pro Trinket is it just looks like a classic USBtinyISP AVR programmer. This

makes it easy to use with AVRdude or Arduino IDE with only minor configuration changes. Before you start, you may

need to install the USBtinyISP USB drivers

Drivers are only required for Windows, if you are using a Mac or Linux, drivers are not required!

Check this page for how to install the driver

Don't forget to plug in the Pro Trinket via a known-good USB cable to start the process. You should see the green

power LED lit and the red bootloading LED pulse indicating that the Trinket is ready to start bootloading. If you've

programmed the Pro Trinket since getting it, you can always get it back to the bootloader state by pressing the small

onboard reset button

Please note: you cannot use the Adafruit USB VID/PID for your own non-Trinket products or projects.

Purchase a USB VID for yourself at http://www.usb.org/developers/vendor/