Assembled board shown for reference only - this is the listing for the BARE BOARD

Assembled boards with ATtiny412 or ATtiny402 are available my other listing

This is a breakout board for the new ATtiny megaAVR x2 series - supports 412, 212, 402, 202 - all the 8-pin megaAVR 1-series and 0-series ATtiny parts. These are highly capable and affordable ATtiny parts - prices are lower than most classic AVR ATtinys with the powerful megaAVR peripherals. These parts are fully compatible with Arduino using my megaTinyCore, too.

New Rev. A now available

The new Rev. A boards are now available - these have the reference designators, and the autoreset circuit is now usable. These are the boards shown in the first and third product picture. If you do not connect the jumper on the back to enable autreset and install the autoreset components, these boards can be used freely for UPDI or Optiboot without auto-reset (see the programming section below for more details).

To clear the Rev. - boards out, they are offered at a 35-cent discount. They are totally suitable for programming with UPDI, or with the Optiboot bootloader without setting the UPDI pin to reset (see the megaTinyCore documentation for more information on these configurations), but not for optiboot with UPDI as reset. If you don't need optiboot with autoreset nor the mounting holes, these boards will work for your purposes.

Warning: The TX and RX lines from the FTDI connector are routed to the "alternate" pins (Arduino pins 2 and 3, physical pins 4 and 5), not the "default" pins (Arduino pins 0 and 1, physical pins 2 and 3). In megaTinyCore versions prior to 2.0.0, the 8-pin parts defaulted to using the "alternate" pins; in 2.0.0 and later, this is no longer the case - on 2.0.0 and later, you must call Serial.swap(1) before Serial.begin() to move Serial to the alternate pins. There is a Rev. B in the works that will move the serial pins to the "default" ones (which is where they always should have been).

Board Features

• 1 LED connected to PA7 (Arduino pin 3)
• 1117-series or compatible voltage regulator
• 4.7k resistor for UPDI programming
• 3-pin header for UPDI programming
• 6-pin header for Serial (FTDI pinout)
• 2 pin Vin header for external power (input to regulator)
• 4 Gnd and Vcc pins - easily power multiple devices from the breakout board without having to make Y-cables!
• All pins broken out to headers at 0.1 pitch

ATtiny Features

• 5 usable I/O pins
• 1.8v~5.5v operation
• up to 4kb of flash
• up to 256b of SRAM (on 1614)
• DAC (1-series parts only)
• 1 PWM pin exposed via Arduino core

BOM

U1 ATtiny 412, 212, 402, 202

C1 1206 0.1uF Cap - decoupling

C2 1206 Output Cap for regulator and power supply filtering (4.7uF or as directed by regulator datasheet)

C3 (If using regulator) 1206 Input Cap for regulator (4.7uF or as directed by regulator datasheet)

C4 Rev. A: 1206 0.1uF capacitor if using autoreset. With Rev. - or if not using autoreset on Rev. A, Do Not Use

R1 1206 4.7k resistor

R2 Rev. A: 1206 10k resistor if using autoreset. With Rev. - or if not using autoreset on Rev. A, Do Not Use

R3 1206 resistor (ballast for LED - 2.2k ~ 220 ohm depending on how bright you like your LEDs)

D1 Rev. A: SOD123 diode with band facing the regulator if using autoreset. With Rev. - or if not using autoreset on Rev. A, Do Not Use

LED1 (optional) 1206 LED, this is connected to PA7 (Arduino pin 3) -

F1 (if using regulator) 1206 PTC fuse (1A max recommended, can replace with jumper if you like to live dangerously or your power supply is already current limited)

U2 (optional) 1117-series or compatible voltage regulator in SOT-223 package (Recommended: LDL1117)

Pin Header - 1x3 for UPDI header, 1x6 for FTDI serial header. 2 1x15 headers for the I/O pins - recommend normal square header for use with DuPont jumpers, or machined pin header for use with breadboard. All 0.1" pitch.

Power header (if using regulator) Your preferred 2-pin power connector (or wires to in-line connector), 0.1" pitch.

Note: Reference designators are missing from the top silkscreen on the Rev. - parts. Refer to images as reference; part locations are:

U1, U2 - obvious

2 1206 parts on either side of UPDI header - R3, LED1

2 1206 parts between UPDI header and U1 - (starting from UPDI header) R1, C1

2 1206 parts between regulator and Vin header (starting from edge of board) - F1, C2

1 1206 part on other side of regulator - C3

3 parts in corner near FTDI header - C4, R2, D1 - Do not use (this is for an autoreset circuit - this is only useful with serial bootloader and UPDI disabled (as it will prevent UPDI programming), such a bootloader will be introduced in a future version of megaTinyCore, but is not currently available)

Programming the megaAVR ATtiny parts

Unlike other AVR microcontrollers, these new parts are programmed via a "UPDI" singlewire interface instead of the SPI-based ICSP protocol. You can easily use a standard Arduino Nano, Uno, or Pro Mini as a UPDI programmer, this is what we use and recommend - see the instructions here:

Make UPDI programmer from Nano/ProMini/Uno

The order of the pins on the UPDI header is UPDI-Gnd-Vcc - this means that if the programmer is connected backwards, the board will not be damaged. The 4.7k resistor is on the breakout board; you do not need to (and should not) use another one.