Dily3217 Scales Down an Arduino Nano Into a Breadboard-Friendly Chip
The Arduino Nano is already a compact board. However, Albert van Dalen has gone a step further. In under 300 mm-squared, the Dily3217 crams (almost) all of the Nano's features into a board that is smaller than the ATmega328P itself.
The secret is the feature-packed ATtiny3217. With the DIL24 form factor, not only is the Dily3217 breadboard-compatible, but it also space-saving friendly.
When asked why he chose the ATtiny3217, van Dalen says:
The ATtiny3217 has the most memory (32k/2048) and I/O pins (21) of the ATtiny series. And because of the QFN-24 package, the chip is tiny. Note that, there is a trend that many new chips are only delivered in very small packages, with a pin spacing of about 0.5 mm.
The ATtiny3217 offers 21 GPIO pins that operate at 5 volts. Like other AVR MCUs, the pins are multiplexed for analog and digital functions. In addition to a 10-bit ADC, there is also an 8-bit DAC available. Like the ATmega328P found in the Uno and Nano, the 3217 has 2 kilobytes of SRAM and 32 kilobytes of program memory.
A critical difference to the Uno and Nano is that the Dily3217 does not have onboard USB support. Instead, there is an FTDI header in the middle of the board for serial communication.
Speaking of missing components, after inspection, you might notice there is not a crystal or ceramic resonator! Microchip has packed an internal 20 MHz RC oscillator into the ATtiny3217's teeny QFN24 package. Since the 3217 is not available in a through-hole version, the Dily3217 effectively converts the MCU into a breadboard-friendly breakout.
Support for the Arduino IDE is available with the megaTinyCore package by Spence Konde. You'll need to include an additional repository for the IDE to be able to install it. The Dily3217 includes the optiboot bootloader so that you can program it over serial, through the FTDI header.
Head over to van Dalen's blog for a detailed write-up for the Dily3217, including how to enable IDE support. While not for sale yet, if you are interested, you can contact him through his website.