We like the AVR 8-bit family and were excited to see Atmel upgrade the series with a USB core. Having USB built in allows the chip to act like any USB device. For example, we can program the chip to ‘pretend’ it’s a USB joystick, or a keyboard, or a flash drive! Another nice bonus of having USB built in is that instead of having an FTDI chip or cable (like an Arduino), we can emulate the serial port directly in the chip. This costs some Flash space and RAM space but that’s the trade-off.
The only bad news about this chip is that it is surface mount only (SMT), which means that it is not easy to solder the way the larger DIP chips are. For that reason, we made a breakout board. The board comes with some extras like a fuse, a 16mhz crystal, USB connector and a button to start the bootloader.
Why not use a Teensy
We also carry a similar board from PJRC called the Teensy . The Teensy uses the same chip so you may be wondering, why did we design a different-but-still-basically-the-same board? We’ve used the Teensy in a few projects and like it a lot but there are a few details that we wanted to change. We wanted…
…a bootloader that would work with avrdude since that is our preferred software
…another LED, for power-good indication
…a 500mA fuse on the USB power-source pin
…mounting holes so we could attach it easily
…reprogramming ISP header so we could program the board directly without the bootloader
…a larger reset button
…all the pins broken out for use with a breadboard
…open source bootloader that works with AVRdude
That doesn’t in any way mean that it is better or replaces the Teensy. Here are some reasons we will still use the teensy for many projects
It’s really really small. A third the size of this breakout
The bootloader that is programmed in uses only 512 bytes (instead of 2K)
It works nicely with Teensyduino and auto-resets right before programming
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