There’s a new I²C chip in town: ATtiny3217

As you may know I’m a fan of the I²C interface. You can find a sensor or board for just about anything that uses this 2 wire protocol. But sometimes you want to use some part that doesn’t work with I²C. Using the ATtiny3217 may be the perfect solution. The Atmel ATtiny3217 is a powerful micro that can interface with your new part or hardware and create an new I²C slave interface. And the best news is that the ATtiny3217 only costs around $1 in quantity one.

The ATtiny3217 is similar to the ATMega328 processor used in the original Arduino boards. It comes in very tiny QFN24 surface mount package or a little larger SOIC package (ATtiny3216, which has a few less features). It has 32KB of flash, 256 bytes of EEPROM, 2KB of SRAM, 22 I/O lines, USART, I²C, SPI, Watchdog, A/D, D/A, and even some custom gates that you can program like a FPGA. It runs at up to 20 MHz and can be programmed with the Arduino IDE or if you want a debugger you can use the Atmel software suite.

There are a few development boards available for this new part.
* Atmel/Microchip sells a board that features this microcontroller called the ATtiny3217 Curiosity Nano.
* Spence Konde (who wrote and supports the development software for the ATtiny3217 using the Arduino IDE) offers the ATtiny3217/1607 dev board.
* LeoNerd sells the ATtiny3217 Development Board.
* Adafruit sells a board that uses the ATtiny817 (little sister to the ATtiny3217) called the Adafruit ATtiny817 Breakout.

I have a made development board too that I will document on this website. It is a Feather compatible board that includes a LiPo Battery charger, FTDI compatible serial port, UPDI programming port, and two I²C QWIIC ports. Here are some pictures of the first prototype:

Other Resources:
* Arduino Core for the ATtiny parts called megaTinyCore. This is an amazing piece of work by Spence Konde! This package allows you to write software for these parts using the Arduino IDE.
* Microchip’s product page for the ATtiny3217 with data sheet.

Note: As of November 2021 these chips are in short supply. Mouser and Digikey are receiving regular shipments, but they go fast. You can also get samples directly from Microchip.