Assembled ATtiny412, new ATtiny, 5 I/O pins, DAC, Arduino support - or ATtiny402 w/out DACDesigned by Azzy's Electronics in United States of America
**Note - pictures are not updated to show Rev. B board with autoreset circuit. Convenient, minimalist development/breakout board for new ATtiny412 (or 402) Over the past several years, Atmel/Microc...Read More…
**Note - pictures are not updated to show Rev. B board with autoreset circuit.
Over the past several years, Atmel/Microchip has been releasing parts based on a new set of peripherals, the megaAVR 0-series and tinyAVR 0/1-series. 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.
Unless marked as Rev. B, all boards are Rev A/Rev. -. On Rev. A, 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. The Rev. B boards have TX and RX routed to the the default pins, with the onboard LED moved to PA3/Arduino Pin 4/physical pin 7. Rev. B boards are now making it into production and will replace the older versions as they sell out. The Rev. B boards also contain a number of new solder-bridge jumpers for advanced functionality - a documentation link on them will be added soon.
The ATtiny 412 and 402 are the top-end 8-pin parts from the tinyAVR 0/1-series 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 (now LDL1117 - with dropout as low as 0.35v!), 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, optionally pre-loaded, Optiboot bootloader allows programming via serial (like a classic Pro Mini).
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. On the ATtiny412 and ATtiny402 parts, due to the limited memory, we do not recommend using Optiboot.
There are two general approaches to using Optiboot on these parts:
Without auto-reset, UPDI enabled. On all boards that do not support auto-reset, and on boards that do if this option is selected, the UPDI/Reset pin will be left as UPDI, and the board can be freely reprogrammed via UPDI. 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 upload - or alternatively, you could adapt your sketch to trigger a software reset. UPDI programming will still be possible. Note that for these boards, 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
With auto-reset, no UPDI. On boards which do support auto-reset (if using optiboot), you may elect to order the board with or without that enabled. If it is, the bootloader will not run on power on; it will only run after a "hardware reset" - it will not run after a normal power on reset. Only after external (reset pin) or software reset; this mimics the behavior of a classic bootloader on (for example) an ATmega328p, and coupled with autoreset provides a very smooth user experience. Warning: This comes with a very large downside: if this option is chosen, you cannot reprogram the board via UPDI unless you use an "HV UPDI" programmer. The RST_EN solder bridge must also be disconnected prior to this.
A third approach is to upload sketches which all have a means of triggering a "software reset" from within the sketch, either from a pin interrupt (the existing autoreset parts could be wired to this pin). With other trigger mechanisms, this could be used in more advanced deployments, such as a device at the far end of a serial line, which resets in response to a specific command0). These schemes allow one to use the bootloader without powercycling the board while also permitting use of UPDI programming - however because they depend on the sketch, they are inherently more "brittle", and that UPDI programming option may become necessary to revive boards during development -in the event of bugs in the application. This method is beyond the scope of this product listing.
If purchased without the bootloader installed, if you later decide that you want it, 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); this pre-bootloading service is intended only as a convenience.
Boards with optiboot preinstalled are bootloaded at the time the order is received. All boards are set to 20-MHz derived clock speeds unless 16 MHz is requested, 4.2 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.
More information on Optiboot and the tinyAVR 0/1-series parts is available in the megaTinyCore documentation.
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.
These are available with an optional CH3490-based serial adapter. All of the bundled serial adapters ship with a 6-pin dupont jumper (20-30 cm, and may be mismatched if multiple serial adapters are purchased Like the basic serial adapters, they're stuck somewhere in the mail.
The "basic" version is a commercially available serial adapter with a serial adapter with a switch on it to select 5v or 3.3v operation and a full-size USB type A male connector (the kind that plugs into a computer or USB hub) (Baite BTE13). When in 3.3v mode, the TX and DTR lines still use 5v logic levels; when connected to a 3.3v boasrd, the series resistor on the TX line of the adapter, and the protection diode on the ATtiny, will work together to keep both parts operating well within manufacturer specified limits.
The Deluxe version is a board of my design - the ones shipping now were hand assembled which is why they are so expensive (I ran out of the basic ones - the deluxe ones are coming out of the ones I use daily for development); we are investigating whether we could get them made at a competitive price. The voltage switch effects both Vcc and the TX and DTR pins. Instead of an invconvenient full size USB connector, these have a common micro USB port. The power LED on the board indicates the selected voltage - Red for 5v and Blue for 3.3V. The regulator used is a high quality LDL1117-series 3.3v adapter, not a rice-grain sized piece of garbage - you should be able to have 5V come in through USB and power a 3.3V project no problem. as long as current does not exceed a half amp. This also ensures that the switch is not forced to handled excessive current. a PTC polyfuse limits current ~if~ you short power and ground. And if you think some of the features listed shouldn't be anything special - know that the reason I designed my own was that I couldn't find any for sale that didn't get at least two of these features wrong.
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