Assembled ATtiny412, new megaAVR ATtiny, 5 I/O pins, DAC, Arduino supportDesigned by Azzy's Electronics in United States of America
ATtiny1614, 3216 assembled boards restocked! Optiboot megaavr ATTiny boards are coming before black friday!
Note - pictures are not updated, they will be updated on 12/1/2019. Convenient, minimalist development/breakout board for new ATtiny412 (or 402) Over the past several years, Atmel/Microchip has bee...Read More…
Note - pictures are not updated, they will be updated on 12/1/2019.
Over the past several years, Atmel/Microchip has been releasing parts based on their new "megaavr" architecture. These use the familiar AVR instruction set and open source avr-gcc compiler used with the classic AVR microcontrollers, but with redesigned and more capable on-chip peripherals and highly competitive prices. The best known of these (among hobbyists, at least) is the ATmega4809, used on the Arduino Uno WiFi Rev.2 and Nano Every. However, there is also an extensive line of ATtiny parts based on this new architecture - and now with my megaTinyCore, there is full Arduino IDE support for these.
The ATtiny 412 and 402 are the top-end 8-pin parts from the megaavr ATtiny product lines - unfortunately they don't seem to have 8Kb parts available, at least not yet. These breakout boards come equipped with your choice of 3.3v or 5v regulator (ZLDO1117 or LDL1117 depending on stock), or no regulator at all (regulator bypassed). Regardless of the regulator option, it can be powered using the two pins in the lower left corner (these are also protected with a PTC fuse), an LED (on PA7, Arduino pin 3), and a UPDI programming header (with the 4.7k resistor on the board). There is a 1x6 pin "FTDI"-style serial header on the bottom edge of the board (no auto reset, as there is no separate reset pin). This board is available with or without autoreset support. Pictures 1 and 3 show boards with autoreset, pictures 2 and 4 show boards without autoreset.
New Optiboot bootloader allows programming with just an external serial adapter (like an Arduino Pro Mini), making these parts easier to use than ever before!
All pins are broken out, and there are 3 Vcc and 3 Gnd pins available, plus the ones on the UPDI and Serial headers so even if you're not using breadboard, you can still easily connect power and ground for multiple external devices.
Board dimensions are 1.1" x 0.85"
The ATtiny402 is the top-end 0-series part in the 8-pin package. The 0-series is intended for low cost applications, and cuts a few features. These are offered as an option for people developing boards that will be produced in large quantities where the cost savings is significant. For hobbyists and one-off projects, the 412 is almost certainly a better deal. The main differences are:
In some of the pictures shown above, the boards are shown with pin header (not included) attached. We recommend:
There are two approaches to programming these 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:
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.
A typical development configuration might have the board connected to a serial port via the 6-pin serial header for serial debug, and to the UPDI programmer via the 3-pin header for uploading new code (as shown in the pictures)
As of megaTinyCore 1.1.2, the Optiboot bootloader is supported for all parts; this works with an external serial adapter (like the 6-pin ones used for the Arduino Pro Mini). Optiboot takes up 512b of flash for the bootloader. In addition to obliviating the need for a UPDI programmer to upload sketches, optiboot allows you to use the same port for upload and serial monitor like a normal Arduino board.
All boards can be purchased with or without a bootloader - the extra fee covers the time to bootload these boards on demand, and connect the jumper to enable autoreset on autoreset boards).
For pre-installed non-autoreset boards, the version of the bootloader installed will be active for 8 seconds after power on, or after a WDT or software reset. So for example, to upload, you would verify sketch, unplug, plug back in, and then do upload. UPDI programming will still be possible (note that you must use UPDI to "burn bootloader" with the non-optiboot board definition selected if you want to switch back to uploading sketches via UPDI).
For pre-installed boards with autoreset support, the autoreset and reset pin will be enabled, and the bootloader will not run on power on, only after external (reset pin), WDT, or software reset. In this case, you can upload without re-plugging the board (like a pro mini), provided you have the DTR pin connected to the DTR pin on your serial adapter. Further UPDI programming is possible only with an HV programmer.
If purchased without the bootloader installed, you may install it using a UPDI by doing burn bootloader (if using autoreset and UPDI pin set as reset, the jumper on the back must be closed after bootloading) - the pre-bootloading service is for convenience so that a UPDI programmer is not required.
Boards with optiboot preinstalled are bootloaded at the time the order is received. 5v boards are set to 20MHz (works at 10MHz and 5MHz too - set from tools menu when you upload), 3.7v sampled BOD, 3.3v boards are set to 10MHz (will also run at 5MHz) 2.6v sampled BOD. No-regulator boards are set to 20MHz/10MHz/5MHz, with BOD disabled to minimize idle power consumption. Because these are bootloaded on-demand, and since UPDI programming is disabled on autoreset boards, if you have different requirements (eg, 16MHz base clock to allow 16MHz/8MHz/4MHz speeds, or different BOD settings), this can be done, just list what you want in order comments.
The linear regulators offered can provide a regulated operating voltage provided Vin in at least 1.3v (ZLDO1117) higher than the operating voltage. These regulators are appropriate when your current requirements are relatively low, and you have access to a power supply with a voltage higher than the operating voltage (max 18v input) - maximum power dissipation, however, is only ~1.2W without adding heatsinks, (that is to say (Vin - Vout)*(current) < 1.2W) so the practical maximum current is much lower.
Example calculations of maximum current when using the regulator:
Vin=12v, Vout=5v. Vin-Vout=7V. 7V*I < 1.2W -> I < 1.2W/7V -> I < 170mA
Vin=7v, Vout=5v. Vin-Vout=2V. 2V*I < 1.2W -> I < 1.2W/2V -> I < 600mA
Only the Vin pin goes through the regulator - all other Vcc pins (including the UPDI and FTI headers) are connected directly to the Vcc rail - so if you have a 3.3v regulator, but connect a 5v serial adapter's 5v line to the board, the board will be running at 5v (this will not harm the board itself, as long as the voltage does not exceed 5.5v - but if you have 3.3V devices connected to it, those may be harmed, so if you have any of those connected, you must use a 3.3v serial adapter or power some other way, and not connect the 5v pin of the serial adapter (the data lines are fine, as serial adapters almost universally have a 1k~2.2k resistor in series with the TX and RX lines which will limit the current to a non-dangerous level, or disconnect the 3.3v devices from the board before connecting the 5v to the board's Vcc), whereas if you supply 5v to the Vin pin, the board will be running at 3.3v.
However - a regulator has a quiescent current that it draws to power itself (0.25mA~0.5mA for these regulators). Hence, if you are running on batteries and using power saving techniques, you want to avoid having a regulator on the board if possible. For example, if running off a LiPo/LiIon battery at 3.7~4.2v, you could set it to run at 10MHz, and use no regulator - approximate power use with a regulator (whether or not you power through the regulator or connect power direct to Vcc), the sleep mode power down current will be ~0.25mA (almost all from the regulator), whereas without the regulator, current in sleep mode power down will be ~0.1uA (0.0001mA) at room temperature - that is, for a project where the chip will spend most of it's time in sleep mode power down, the battery life may be 2,500 times longer without the regulator.
If powering from batteries w/out a regulator, you need to be careful not to connect external power directly to Vcc (including from a serial adapter or UPDI programmer) while the battery is connected.
On boards where there is no regulator, the PTC fuse is still present (in series with Vin), and the regulator is bypassed by a 0-ohm resistor, so you can still use the Vin pin power the board to get the benefit of overcurrent protection. See picture 3 for an example of what the "no regulator" looks like.
megaTinyCore now 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) - if you wish to use this with autoreset and bootload it yourself, you must bootload the board with an Optiboot board definition selected, with the UPDI pin configured as reset (note that this makes further UPDI programming impossible without an HV programmer), and then solder the two small contacts on the bottom of the board in order to enable autoreset (which would have blocked UPDI programming to bootload were it connected at that time). After that, it can be programmed with just a serial adapter (same 1x6-pin header as used on the Arduino Pro Mini and others).
More information on Optiboot and the megaavr ATTiny parts is available in the megaTinyCore documentation.
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