Commit f5a6a22

* The overclocked options at 24/25 MHz have been found to generally work around room temperature when running at 5v. The faster ones - while they can be stable with solid 5v supply at room temperature, this is right on the edge of what these parts can do. I have specimens that will run at 5.0v but not at 4.8, for example, meaning that it would work powered by some USB ports, but not others (those range from 4.7 to 5.3v) and they are of course extremely sensitive to noise on power rails. External oscillators work more reliably than the internal one when overclocking, but they generally cost about as much as the microcontroller itself and are gross overkill (in terms of accuracy) for what most arduino folks want from them.

* There's no dedicated reset pin. So there is no way to do the traditional autoreset circuit to reset the chip to upload with a bootloader unless you disable UPDI (requiring HV UPDI to undo - I've got a half dozen boards that are bricked until I have time to get an hvupdi programming setup together to resurrect them). Either you manually power cycle it just prior to trying to upload, or you have some sort of ersatz-reset solution coupled to an autoreset circuit, or handle it in some other bespoke way. Regardless of the approach, short of disabling UPDI to get a reset pin (which is irreversible without an HV UPDI programmer), none of them are as convenient a development cycle as we're used to. In most cases, the most convenient development configuration is to simply use UPDI programming, and leave any serial connection open while programming via UPDI using a programmer on a different port.

* The overclocked options at 24/25 MHz have been found to generally work around room temperature when running at 5v. The faster ones - while they can be stable with solid 5v supply at room temperature, this is right on the edge of what these parts can do. I have specimens that will run at 5.0v but not at 4.8, for example, meaning that it would work powered by some USB ports, but not others (those range from 4.7 to 5.3v) and they are of course extremely sensitive to noise on power rails. External oscillators work more reliably than the internal one when overclocking, but they generally cost about as much as the microcontroller itself and are gross overkill (in terms of accuracy) for what most arduino folks want from them.

* There's no dedicated reset pin. So there is no way to do the traditional autoreset circuit to reset the chip to upload with a bootloader unless you disable UPDI (requiring HV UPDI to undo - I've got a half dozen boards that are bricked until I have time to get an hvupdi programming setup together to resurrect them). Either you manually power cycle it just prior to trying to upload, or you have some sort of ersatz-reset solution coupled to an autoreset circuit, or handle it in some other bespoke way. Regardless of the approach, short of disabling UPDI to get a reset pin (which is irreversible without an HV UPDI programmer), none of them are as convenient a development cycle as we're used to. In most cases, the most convenient development configuration is to simply use UPDI programming, and leave any serial connection open while programming via UPDI using a programmer on a different port.

* It takes 512b of flash - which may be a substantial fraction of the total.

* The overclocked options at 24/25 MHz have been found to generally work around room temperature when running at 5v. The faster ones - while they can be stable with solid 5v supply at room temperature, this is right on the edge of what these parts can do. I have specimens that will run at 5.0v but not at 4.8, for example, meaning that it would work powered by some USB ports, but not others (those range from 4.7 to 5.3v) and they are of course extremely sensitive to noise on power rails. External oscillators work more reliably than the internal one when overclocking, but they generally cost about as much as the microcontroller itself and are gross overkill (in terms of accuracy) for what most arduino folks want from them.

* There's no dedicated reset pin. So there is no way to do the traditional autoreset circuit to reset the chip to upload with a bootloader unless you disable UPDI (requiring HV UPDI to undo - I've got a half dozen boards that are bricked until I have time to get an hvupdi programming setup together to resurrect them). Either you manually power cycle it just prior to trying to upload, or you have some sort of ersatz-reset solution coupled to an autoreset circuit, or handle it in some other bespoke way. Regardless of the approach, short of disabling UPDI to get a reset pin (which is irreversible without an HV UPDI programmer), none of them are as convenient a development cycle as we're used to. In most cases, the most convenient development configuration is to simply use UPDI programming, and leave any serial connection open while programming via UPDI using a programmer on a different port.

* It takes 512b of flash - which may be a substantial fraction of the total.

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.

This matches the megaTinyCore 412/402 Rev. - and Rev. A breakout boards below.. On bootloader . **In 2.0.0 and later, this is no longer the case!** You must call Serial.swap(1) prior to Serial.begin() to move it to the alt pins (or connect your adapter to pins 0 and 1 instead of 2 and 3). It should never have been done that way in the first place. Rev. B of the breakout boards that has the FTDI header tied to the standard serial pins is now available.

* The overclocked options at 24/25 MHz have been found to generally work around room temperature when running at 5v. The faster ones - while they can be stable with solid 5v supply at room temperature, this is right on the edge of what these parts can do. I have specimens that will run at 5.0v but not at 4.8, for example, meaning that it would work powered by some USB ports, but not others (they range from 4.7 to 5.3v) and they are of course extremely sensitive to noise on power rails. External oscillators work more reliably than the internal one when overclocking, but they generally cost about as much as the microcontroller itself and are gross overkill (in terms of accuracy) for what most arduino folks want from them.

There's no dedicated reset pin. So there is no way to do the traditional autoreset circuit to reset the chip to upload with a bootloader unless you disable UPDI (requiring HV UPDI to undo - I've got a half dozen boards that are bricked until I have time to get an hvupdi programming setup together to resurrect them). Either you manually power cycle it just prior to trying to upload, or you have some sort of ersatz-reset solution coupled to an autoreset circuit, or handle it in some other bespoke way. Regardless of the approach, short of disabling UPDI, none of them are as convenient a development cycle as we're used to. In most cases, the most convenient development configuration is to simply use UPDI programming, and leave any serial connection open while programming via UPDI using a programmer on a different port. Note that the 2-series 20 and 24 pin parts have enhancements that make a bootloader capabloe of providing a better developer experience possible.

* The overclocked options at 24/25 MHz have been found to generally work around room temperature when running at 5v. The faster ones - while they can be stable with solid 5v supply at room temperature, this is right on the edge of what these parts can do. I have specimens that will run at 5.0v but not at 4.8, for example, meaning that it would work powered by some USB ports, but not others (they range from 4.7 to 5.3v) and they are of course extremely sensitive to noise on power rails. External oscillators work more reliably than the internal one when overclocking, but they generally cost about as much as the microcontroller itself and are gross overkill (in terms of accuracy) for what most arduino folks want from them.

There's no dedicated reset pin. So there is no way to do the traditional autoreset circuit to reset the chip to upload with a bootloader unless you disable UPDI (requiring HV UPDI to undo - I've got a half dozen boards that are bricked until I have time to get an hvupdi programming setup together to resurrect them). Either you manually power cycle it just prior to trying to upload, or you have some sort of ersatz-reset solution coupled to an autoreset circuit, or handle it in some other bespoke way. Regardless of the approach, short of disabling UPDI, none of them are as convenient a development cycle as we're used to. In most cases, the most convenient development configuration is to simply use UPDI programming, and leave any serial connection open while programming via UPDI using a programmer on a different port. Note that the 2-series 20 and 24 pin parts have enhancements that make a bootloader capabloe of providing a better developer experience possible.

* The overclocked options at 24/25 MHz have been found to generally work around room temperature when running at 5v. The faster ones - while they can be stable with solid 5v supply at room temperature, this is right on the edge of what these parts can do. I have specimens that will run at 5.0v but not at 4.8, for example, meaning that it would work powered by some USB ports, but not others (those range from 4.7 to 5.3v) and they are of course extremely sensitive to noise on power rails. External oscillators work more reliably than the internal one when overclocking, but they generally cost about as much as the microcontroller itself and are gross overkill (in terms of accuracy) for what most arduino folks want from them.

There's no dedicated reset pin. So there is no way to do the traditional autoreset circuit to reset the chip to upload with a bootloader unless you disable UPDI (requiring HV UPDI to undo - I've got a half dozen boards that are bricked until I have time to get an hvupdi programming setup together to resurrect them). Either you manually power cycle it just prior to trying to upload, or you have some sort of ersatz-reset solution coupled to an autoreset circuit, or handle it in some other bespoke way. Regardless of the approach, short of disabling UPDI, none of them are as convenient a development cycle as we're used to. In most cases, the most convenient development configuration is to simply use UPDI programming, and leave any serial connection open while programming via UPDI using a programmer on a different port. Note that the 2-series 20 and 24 pin parts have enhancements that make a bootloader capabloe of providing a better developer experience possible.

* 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! Whereas the previous 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. As always, external oscillators work more reliably than the internal one when overclocking, but they generally cost about as much as the microcontroller itself and are gross overkill (in terms of accuracy) for what most arduino folks want from them.

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 have been announced in the full range of flash size options - Hopefully it won't be a repeat of the 3214 which was in the ATpacks, but never actually shipped, and had all references to it removed. 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 expanded RAM on the 4k and 8k parts goes a long way to making those parts more practical option.

* 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! Whereas the previous 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. As always, external oscillators work more reliably than the internal one when overclocking, but they generally cost about as much as the microcontroller itself and are gross overkill (in terms of accuracy) for what most arduino folks want from them.