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

**Assembled boards with 1624, ATtiny1614 or the new ATtiny3224 are available in my other listing

This is a breakout board for the ATtiny 0/1/2-series with 14 pins. These feature the latest and greatest peripherals in a low cost tinyAVR package (in fact, they are in most cases cheaper than classic tinyAVRs), including the 3224, 1624, 824, 424, 3214, 1614, 814, 414, 1604, 804 - all the 14-pin tinyAVR 2-series, 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.

Available Versions

• Rev. B - yellow solder mask, designed prior to release of the 2-series, these boards are 0.1" wider (hence do not fit into DIP-40 spacing sockets). Pins are only marked by Arduino Pin Number (Numeric values for pin numbers are deprecated by megaTinyCore - PIN_Pxn is preferred now), and pin functions not marked. We have 7 more bare ones and the stencil has been sold already. Take em all for $8
• Rev. C - blue solder mask, improved markings including both Port/bit, not just Arduino pin numberes, and the new color scheme addresses readability complaints. Unfortunately, during layout tweaking, a section of trace a few mm long was omitted, and onboard LED is nonfunctional. I considered the assembled boards non-salable simply based on how long it too me to figure out that the problem was just the LED, because everyone tests with blink, including me, and it took me a while. So these are only available as bare boards. There are at least 134 boards plus the stencil, Take em all and any others I happen to find for only $100 - well under a buck a board!
• Rev. D - Most recent production version, As rev C, but with the corrected connection to the LED.
• Rev. E (no timeline as no issues other than silkscreen enhancements) - Use white silkscreen within each checkbox to improve contrast of markings made to indicate installed components. Add marking box to indicate F-spec temp rating (this is marked on the chip only on 0 and 1 series (*); it has a significant impact on how aggressively parts can be successfully overclocked), and mark PB0 and PB1 with their I2C functionalities.

The biggest change between Rev B or earlier vs C amd later is tje size. They're narrower than the old ones: Now the rows of pins on the edges are 0.6" apart, the same width as a Nano - and you know what that means: You can also put machined pin header on them, facing down, and plug them into a Wide DIP socket, This works great with my prototyping boards, especially the new 1.5" x 4" DIP-48 ones. The machined pins are also far better for use with breadboards, since they don't deform te contacts in the holes like normal pin header. We switched to dark blue solder mask to improve readability of solder mask, pins are now marked with both the pin name in Pxn notation (eg, PB2 is the pin corresponding to bit 2 of PORTB, and can be referred to if using my Arduino core as PIN_PB2 - since the functions are based on this, using this notation makes it easy to port your design between tinyAVR parts with different numbers of pins. For example, you want to output some PWM on 2 pins, so you choose PB0 and PB1. If you later realized that you needed more pins than you thought, and switch to a 20-pin part, if you used numbers to refer to the pins, those number would be different, and have to be changed, while if you called them PIN_PB0 and PIN_PB1 (and did the same with all other pin references) you could be assured that moving from a 1624 to a 1626, 3226, or 3227, all of the pins you'd already chosen would still have the same capabilities as they did on the 1624. I personally have found this to be indispensable when porting snippets of useful code around.

We have also improved markings around the groups of jumpers on the back for making use of the DTR and CTS lines, and changed the default connection for CTS (which can be be either grounded, for software that uses that to detect the present of hardware, tied to a pin, namely PB1, which is the XCLK pin when the other pins are used as USART, which makes it possible to implement synchronous serial mode with the same 6-pin connector. Finally, and what is connected by default, the CTS line can be connected to UPDI. This allows a special programmer/serial adapter to provide programming and serial through the FTDI connector. An attempt was also made to clarify the options for the DTR line: direct to PB0 (XDIR if that feature is used, which would enable convenient connection over the 6-pin header RS485 transcievers for longer distance transmission), OR it can be part of the normal autoreset circuit. Unfortunately this is a real pain to use on on tinyAVRs, since you need HV to reprogram them which means you have to disable the autoreset and it's diode to Vdd. These convenience options synergize with the API extensions offered though megaTinyCore See the mTC Serial Reference for more information about how almost all USART functionality is exposed in Arduino via simple and backwards compatible API exertions.

This is a breakout board for all of the "modern" ATtiny parts in SOIC-14 pin packages. They are numbered like: ATtinymmd4 where mm is flash size is kb, d is the series, 0, 1 or 2, and the 4 indicates that it's the 14-pin version. The 8-pin parts end in 2, 20-pin ons end in 6, and 24-pin ones in 7 (my understanding is that the 14, 20, and 24 pin versions use the same die; a complication resulting from this may be the reason that we saw so few 8-pin tinyAVR parts released, as those appear to have a different die.

All of the modern tinyAVR devices are highly capable and affordable - prices are lower than most classic AVR ATtiny devices (as with EVERYTHING since the 2016 AVR revolution) - while the peripherals use the latest and greatest technology (let's face it - the classic AVR peripherals had been getting a little stale. Actually, they'd been stale for a while). As far as I can tell, Microchip tests out their new technology on a tinyAVR before bringing it to a full sized chip most of the time. The tinyAVR 1-series brought us the Type D high speed async timer which then showed up in 2020 on the DA-series - and while the headline features of the DB-series were entirely novel, the only other changes that showed up in the DA/DB series were evolutionary. Now, in 2021, the amazing new fully differential ADC wth Programable Gain Amplifier (PGA) is featured on the 2-series tinyAVRs; this has been announced for the AVR EA-series line of full size parts for future release. These parts are fully compatible with Arduino using my megaTinyCore, and you can access the full functionality of the new ADC through a handful of new functions, or use analogRead() for backwards compatible ADC functionality.

Board Features (dependent on customer-installed parts)

• Rev B+: ENIG surface treatment
• 1 LED connected to PA7 (Arduino pin 3, PIN_PA7)
• 1117-series or compatible voltage regulator
• series resistor for UPDI programming (recommended value 470 ohm)
• 3-pin header for UPDI programming
• 6-pin header for Serial (FTDI pinout)
• 3 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.
• Rev. C/D only: New narrower form factor - same width as a nano!
• Rev. C/D only: Pads for a 3225 oscillator (not crystal) if you happen to need one.
• Rev. C/D only: Improved solder bridge options related to CTS/DTR, extended silkscreen info.
• Rev C Only: Decorative pads for an LED (not connected internally).
• All non-C Rev: pads for 1206 LED and resistor tied to PA7 to blink for debugging.

ATtiny Features

• 11 usable I/O pins
• 1.8v~5.5v operation
• up to 32kb of flash
• up to 3k of RAM on 2-series, 2k on 1- series.
• Unified address space - no need to use PROGMEM or pgm_read_byte - anything declared const doesn't need to be copied to RAM!
• DAC (1-series parts only)
• Hardware SPI, TWI, and Serial. 2-series has 2 serial ports.
• 8 PWM pins exposed via Arduino core (6 pins on 2-series or 0-series, as they lack Timer D)
• Unique and powerful ADC:
• The 1-series has two 10-bit identical ADCs, ADC0 (used by megaTinyCore for analogRead) and ADC1. I think they were meant to be triggered simultaneously to provide a standin for a differential ADC, but you can do other things, like use one normally while leaving the other in free running mode (maybe even with the window comparator enabled)
• The 2-series parts are the first modern AVRs with a true differential ADC with programmable gain. It's a 12-bit ADC, supporting single ended or differential input. The amplifier can be used in both single ended and differential mode, 1x, 2x, 4x, 8x, and 16x gain (1x appears to be meant as a buffer for high impedance signals). The ADC is lightning fast.
• All modern AVRs feature accumulation of multiple samples, but while the 0-series and 1-series only support 64 samples (and the DA/DB 128), the 2-series can accumulate 1024 samples. With the usual technique of oversampling and decimation, would permit 17-bit readings (realistically, not all of those bits are signal - some are just noise)
• Configurable Custom Logic (2 CCL logic blocks on 0/1-series, 4 on 2-series) and event system allow you to set up actions that happen without CPU intervention. It's almost like a very very small FPGA that's simple enough to program directly:
• Divide a clock by a power of two
• Generate wierdo custom serial protocol to talk to things like WS2812alikes.
  • Route the next 150 WS2812-like LEDs worth of data into three strings of 50 lights (so those strands would each display different colors potentially) then forward the rest of the data to any downstream device
• Re-route serial ports onto other pins.
• On chip analog comparator or comparators (3 on 1-series, 1 on 0/2-series).
• Overclocks very well - 50% overclock at 5v is easy, and can be done even with the internal oscillator.
• Arduino wrappers for Event, Logic, Comparator, plua includes compatible Servo, SD card, WS2812 (Neopixel), and other libraries optimized for these parts.

BOM

* 4.7uF or as directed by regulator datasheet ** if Y1 is installed, cut the bridge between PA3 and the through hole normally connected to it for best results. 32 MHz is very possible with solid power supply and external clock.

Skip the regulator, but keep the fuse

If you plan to run directly off a battery (ex, a protected LiPo battery), but still want the PTC fuse protecting the power from battery, a 2512 0-ohm resistor can be soldered between the pads for the regulator tab and pin furthest from the fuse to jumper around the regulator; this will connect the fuse (and hence Vin header) directly to Vcc.

You'll want some pin header, if you don't already have plenty

Additionally, you will almost certainly want some 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. Beautiful, colorful pin header (looks great on social media posts) is available for an added fee.

Programming the modern tinyAVR parts

Unlike older ("classic") AVR microcontrollers, these new parts are programmed via "UPDI" single-wire interface based closely on half-duplex UART serial with autobaud (indeed, it would appear that the UPDI interface is simply a modified UART that always operates in half-duplex single wire mode with autobaud.

In the past the standard in Arduino circles was to use an Arduino Nano as the programmer, running "JTAG2UPDI" - unfortunately that firmware was always rather buggy, and unlike the analogous firmware for programming classic AVRs (Arduino as ISP), the source code is actively hostile to someone wishing to modify it. I worked for months and was never satisfied with the results. We now recommend using the SerialUPDI tool included with megaTinyCore (or pyupdi as a standalone tool - it works much the same way), with an ordinary TTL serial adapter, with the addition of a resistor and/or diode. We provide a number of configuration options that can be get the highest performance your hardware is capable of (it depends on the OS, the serial adapter and the hardware; 57600 baud works everywhere without any compatibility options, while 921600 baud almost always does. See the SerialUPDI guide

Optiboot and Autoreset

megaTinyCore supports the Optiboot bootloader for serial uploads (though you still need a UPDI programmer to bootload the board - our assembled boards are now available with optiboot preinstalled). Unfortunately, on all tinyAVR parts except the 20 and 24-pin 2-series, there is either a UPDI pin or a reset pin. If you make the pin reset, you need to use an HV programmer if you ever want to reprogram it with UPDI. The 20 and 24-pin 2-series parts have the option to use PB4 as the alternate reset pin (configured via fuses). We do not recommend the use of Optiboot on 14-pin boards or any 0/1-series boards. The experience is substantially better on the parts with alternate reset option. Note that support for routing the autoreset pulse to PB4 was added in Rev. C of this board.

More information on Optiboot and the tinyAVR 0, 1, and 2-series ATtiny parts is available in the megaTinyCore documentation.

Quantity discounts and available versions

You get quantity discounts in one of two ways: * Either the normal way, by buying the current production model in quantity greater than 5 (We greatly prefer multiples of 5. The boards are 20mm x 50mm, so I get 10 on a 100mm x 100mm "poor man's panel". 5 is a half panel, so they'll stack nicely - complete panels that stack exactly like that are less likely to be damaged in shipping (this is very rare, but it does occasionally happen. A stack of identical panels tends to act like one block while otherwise they an also slide against each other. Oh, and the past three times I ENTIRE LOT of remaining inventory from a previous revision and it's stencil ($25 value included free!). Pile of Rev. C's is now a small enough pile that that + the FREE stencil is a grand way to get a huge number of no-built in-LED, but otherwise identical to our latest version of 14-pin tinyAVR breakout boards. It seems implausible to try to clear out 300 boards at a time like that - but half that? seems plausible

* Starting in 2020, Microchip stopped marking newly released parts with the temperature grade (so DA-onwards, but not tinyAVR 0/1). This is very unfortunate. Their support people will take the lot codes and tell you, but they don't print it on the part anymore. No idea why - but it sure would make my life easier if I was a crooked assembly house looking down the BoM "U1 AVR128DB48-E" adding "AVR128DB48-I" to their parts order, while billing the customer for E-spec parts. Even if they had kept marking it, the new letters are less secure. Before they used U, F, and N. Top change any of those into another you need to both erase and draw lines. That's harder than changing an I to an E would be (just add lines) but that's irrelevant: they don't print an E or an I on the part. I don't understand why this was done, or how it's in the interest of anyone other than third party bad actors, but c'est la vie.