| Specifications | ATtiny424 | ATtiny824 | ATtiny1624 | ATtiny3224 |
|---|---|---|---|---|
| Availability | Since Q2 2021 | Since Q2 2021 | Since Q1 2021 | Since Q4 2021 |
| Flash (program memory) | 4096 bytes | 8192 bytes | 16384 bytes | 32768 bytes |
| Flash w/Optiboot | 3584 bytes | 7680 bytes | 15872 bytes | 32256 bytes |
| RAM | 512 bytes | 1024 bytes | 2048 bytes | 3072 bytes |
| EEPROM | 128 bytes | 128 bytes | 256 bytes | 256 bytes |
| Bootloader (optional) | Optiboot (not recommended) | Optiboot (not recommended) | Optiboot (not recommended) | Optiboot (not recommended) |
| Feature | Specification |
|---|---|
| GPIO Pins | 12 (11 usable) |
| ADC | 12-bit, differential w/PGA |
| ADC Channels | 9, 7 of which can be neg. diff. pin. |
| DAC | Internal for AC ref only |
| Comparator | 1 |
| PWM Channels ** | 6 |
| Timer Type B | 2 |
| Timer Type D | No |
| CCL logic | 4 LUTs, 12 of 12 inputs |
| Interfaces | UART (2), SPI, I2C |
| Millis Timer | TCA0, TCB0, TCB1 (default), RTC |
| RTC crystal | Optional 32KHz TOSC1, TOSC2 |
| Clock Sources | Internal osc @ 16 or 20 MHz or ext. clock |
| Frequency (rated) | Up to 5 MHz @ 1.8V, 10 @ 2.7V, 20 @ 4.5V |
| Frequency (max * ) | Internal runs up to 36, and works @ 32 MHz |
| Package | SOIC-14, SSOP-14 |
| B.O.D. voltages | 1.8, 2.6 (for 3-3.3v systems), and 4.2 (for 5V systems) |
| B.O.D. voltages | "unqualified" 2.1, 2.9, 3.3, 3.7, 4.0 |
The "unqualified" BOD voltages are not listed in the datasheet, but were referenced in early versions of headers, just like the 0/1-series. They appear to work, I take them being described as "unqualified" to mean that they are not guaranteed by Mirochop.
These parts do not support an external HF crystal, only an external clock, and/or a watch crystal for the RTC.
| MHz | Source | Notes |
|---|---|---|
| 20 | Internal | Default, typical for 5V systems |
| 16 | Internal | Typical for 5V systems. Some libraries may work better at this speed. |
| 10 | Internal | Typical for 3.3V systems |
| 8 | Internal | Typical for 3.3V systems |
| 5 | Internal | Typical for 1.8V - 2.5V systems |
| 4 | Internal | Typical for 1.8V - 2.5V systems |
| 1 | Internal | |
| 20 | Internal, tuned | 16 MHz OSC selected by fuse can be tuned up to 20 no problem. |
| 16 | Internal, tuned | 20 MHz selected by OSCCFG fuse can be tuned down to 16 no problem. |
| 12 | Internal, tuned | 16 MHz can be just barely tuned down to 12. 20 MHz gets tuned up to 24 and prescaled. |
| 20 | External Clock | External clock goes to CLKI (PA3). Minimize any load on this pin, including even short wires. HF stuff is very picky. |
| 16 | External Clock | As above. |
| 10 | External Clock | As above. |
| 8 | External Clock | As above. |
| 24 | Internal, tuned | OVERCLOCKED, usually fine @ 5v and room temperature. |
| 25 | Internal, tuned | OVERCLOCKED, usually fine @ 5v and room temperature. |
| 30 | Internal, tuned | OVERCLOCKED, may be unstable. |
| 32 | Internal, tuned | OVERCLOCKED, may be unstable. |
| 24 | External Clock | OVERCLOCKED, usually fine @ 5v and room temperature. Uses CLKI/PA3 as above. |
| 25 | External Clock | OVERCLOCKED, usually fine @ 5v and room temperature. Uses CLKI/PA3 as above. |
| 30 | External Clock | OVERCLOCKED, may be unstable. Uses CLKI/PA3 as above. |
| 32 | External Clock | OVERCLOCKED, may be unstable. Uses CLKI/PA3 as above. |
When external clock is used as system clock source, PA3 cannot be used for any other purpose (obviously) - all control over that pin is taken by CLKCTRL.
All else being equal, your chances of reaching an aggressive overclock are better with external clock vs internal, and with the extended temperature range parts instead of normal ones.
- The overclocked options at 24/25 MHz have been found to generally work around room temperature when running at 5v. For faster speeds, initial results seem to imply that the 2-series parts are significantly more capable of handling higher operating frequencies compared to the 0/1-series, and that with solid 5v supply, 32 MHz at room temperature may be good enough for practical use, even from the internal oscillator! Whereas the previous tinyAVR parts collapsed at around 30-32 MHz running from internal oscillator, that isn't seen until the mid 30's on the 2-series parts.
The tuned options are new in 2.4.0 - see the tuned internal oscillator guide for more information before using these options. They require running a tuning sketch on your chip.
The smallest pincount of the tinyAVR 2-series parts - (so far there is no word on what Microchip's plans are for the 8-pin package, but everyone I've spoken to is worried about the future of AVRs in 8-pin packages).
These are "available" in the full range of flash sizes (although "available" is a funny word during the Great Chip Shortage; in some cases it means that they will ship tomorrow, other cases, in 10-12 months).
Notice that some 1-series features - mostly the extravagances of the "golden" 1-series parts, but also the type D timer - are gone, while the second type B timer (thankfully) is present in all sizes. The main features though are the fancy ADC, and the second USART - as well as a 32k version with 3k SRAM. The Event System is also normal instead of wacky like the 0/1-series, and there are twice as many CCL logic blocks. The expanded RAM on the 4k and 8k parts goes a long way to making those parts more practical option.
The super ADC can accumulate 1024 samples in a single burst read; decimation of the accumulated value so all of the digits are meaningful can give up to 17-bits of accuracy. For advanced ADC functionality, several new functions are provided, see ADC section of the main readme for more information.
Optiboot is supported, but unlike the higher pincount 2-series devices, you can't have an alternate reset pin here (the pin it can be moved to doesn't exist), so these have the same reset-pain as the 1-series; this is why optiboot is marked 'not recommended' even on parts that have plenty of flash. We default to TCB1 for millis, since there is no type D timer, and because we have TCB0 for tone or TCB-dependant libraries, and TCA0 is more likely to be needed than a second TCB - taking over TCA0 seems to be quite popular; TCB1 also has the additional benefit of having the lowest overhead both for the interrupt millis/micros.
With no critical hardware differences, the same breakout boards we have been selling for the ATtiny1614 and 1614 can be used. We do have a new version in the works with improvements across the whole family, with better silkscreen (including both Pxn notation and key functions, ex. SDA, TX/RX, etc), slightly narrower 0.6" spacing between the rows of pins (for use with sockets and/or prototyping board that caters to that widely used spacing), and support for an external 3.2 x 2.5mm oscillator to supply F_CPU if you really feel you need that.
*Maximum frequency that the the internal oscillator will reach when tuned upwards until it crashes, and the maximum frequency the part actually runs at (based on cursory, not rigorous testing - the parts that ran for a few milliseconds without crashing or failing to perform correct arithmetic with a few unsigned longs was enough to be considered "working") are reported. Both are at 5.0V and are typical values determined experimentally, and the parts may not function reliably at those speeds under more realistic conditions. Maximums vary between individual specimens. Don't rely on parts exceeding manufacturer specifications.
** PWM channels exposed with default configuration via analogWrite(). TCA0 is in split mode, and the type B timer(s) are not used for PWM.