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Comment by auxym | Hacker News Reader

All micros require separate hardware to flash it, no? Some is cheap (stlink), some are a few hundred dollars, but still.

Unless you have a USB bootloader programmed on the chip, but you still need the adapter to flash the bootloader in the first place.

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Not at all! Many devices can be flashed over USB, for example. Many STM32 devices come with a bootloader factory programmed in a read only area that implement USB DFU. Many user-provided software bootloaders can do the same on many other devices. Including the attiny85 using bit banging!

And of course with wireless enabled microcontrollers one can update over the air. Nordic NRF5x over Bluetooth for example, or ESP32 over WiFi.

I think what the parent is getting at is that, because the ATtiny85 has so few pins, programming it usually requires it to be removed from the target circuit.

An MCU is a chip in a package that just cannot interface with anything your consumer PC or notebook comes with. You'll need an adapter in any case.

That said, lots of current MCUs come with UART, I2C and/or USB bootloaders allowing to erase/program (if not disabled). This bootloader is typically included in factory ROM, not to be programmed by you or a third party.

What? Why couldn't an MCU interface with my computer? It's not like it has special electrons or something in it. I regularly program atmega chips with a cable I made that plugs into the parallel port on the back of any computer that has one. If you have a couple GPIO pins on a motherboard, you can probably program almost any MCU with with it.

The only exception is if the motherboard GPIO was say 3.3v and you had a 1.8v only MCU, but level shifters aren't exactly expensive.

So do you jam the chip into the parallel port? Or do you...use an adapter?

I don't see the difference if it's just a parallel cable. Do you jam an STM32 into a USB port?

> Do you jam an STM32 into a USB port?

I unplug my phone for a moment, or use one of several identical cables I have lying around. If this thing needs a dedicated cable then that seems just as annoying in practice as needing a dedicated "programmer" box.

Another exception is the esp32-c3, which includes a jtag debugger inside the chip (not on board, inside the same die)

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