# obdev/v-usb

A Firmware-Only USB implementation for Atmel's AVR Microcontrollers

Repository: https://github.com/obdev/v-usb
Canonical: https://ross.abutalabs.com/products/v-usb
Language: Assembly
License Family: other
Last push: 2026-08-26T14:47:54+00:00

## Health v2 (maintenance only)
Score: 77/100 (v2, computed 2026-09-02T17:46:02.011165+00:00)
- activity 99, release rhythm 35, longevity 100
- inputs: {"age_days": 5018, "days_push": 7, "days_rel": null, "gap_med": null, "n_releases_24m": 0}
- flags: no_releases, no_license
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 1310, forks 262 (observed 2026-08-28T04:04:19.903400+00:00)

## What it is
V-USB is a firmware-only USB driver for Atmel AVR microcontrollers, implementing low-speed USB in software without dedicated USB hardware. It ships as a driver library (C and assembly) with examples for building USB devices on small MCUs.

## Use cases
- add USB support to an AVR microcontroller without USB hardware
- build a custom HID device on an ATtiny85
- implement low-speed USB in firmware
- make a DIY USB keyboard or gamepad with AVR
- bit-bang USB on a cheap microcontroller

## When to choose
- you use an AVR chip lacking a hardware USB peripheral
- you only need low-speed USB (1.5 Mbit/s) such as HID devices
- you want a small, proven, license-free driver for tiny MCUs

## When to avoid
- you need high- or full-speed USB throughput
- your target MCU is not an AVR
- you need USB host mode - this is device-side only

## Facets
- artifact type: library
- maturity: maintenance
- function: embedded, sdk, developer-tools
- domain: embedded-systems, hardware, developer-tools
- platform: embedded, cpp, c
- tags: usb-driver, avr, firmware, bit-banging, low-speed-usb, microcontroller

## Member repositories
- obdev/v-usb (main) score 77

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:04:19.903400+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-30T04:49:56.132410+00:00, confidence not recorded.
  - readme: https://github.com/obdev/v-usb (fetched 2026-08-28T04:04:19.903400+00:00, sha 8854335ad040)
- Data as of 2026-08-30T08:39:29.467469+00:00.