Attiny85 to usb??

Can I just connect the Attiny85 to a usb port without any usb to serial adapter? Because All the tiny attiny85 based devboards like Adafruit trinket doesn't seem to have those U2S adapters - in fact, the attiny85 is the only chip on the board, others are all components like resistors or leds. Anyways can I add a usb port to my attiny85 devboard just by soldering the two directly together? On my atmega328 breadboard arduinos I had to program them with the adafruit ftdi friend

There is an extension to the arduino IDE that will allow these to act as USB devices, they also have a small bootloader on board so they can be programmed directly from the IDE

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You can if you put code based on vusb ( this is a way of faking usb - it's not standards compliant, but almost always works) - normally this is done in the bootloader, since people want to program it over usb. This takes up a significant amount of flash that you could otherwise use for your code.

There are a few other hardware components you need (resistors and zener diodes) for vusb.

V-USB is a software trick to connect to USB1.1 protocol. DigiSpark and Trinket are likely the 2 best commercial products. But the trick also works on the Atmega328P.

The single most critical component in the USB interface are 2x 3.6V zener diodes.

I have several V-USB projects here.

Other forum links:
Here and here


can I somehow connect an attiny85 or atmega328 to a usb a port??? without any special chips like ftdi??

Using VUSB, yes. Not sure how easy / hard to use with arduino. It's a little flaky, compatibility is marginal, but it does mostly work (despite making a mockery of the spec). Be sure you understand the limitations by carefully reading the documentation.

I recommend using a chip that has native usb on it though, like the 32u4

can I somehow connect an attiny85 or atmega328 to a usb a port??? without any special chips like ftdi??

you mean like the CH430G and CP2102 USB to TTL Serial converters?


Maybe you should consider changing the subject of your post to give a little more meaning.

The type of USB-port does not matter - it's the role of the port being the host that is important here.

// Per.

@PocketHarambe101, do not cross-post. Threads merged.