i2c.net
Interactive tool

i2c connector compatibility checker

Will it plug in? Across Qwiic, STEMMA QT, STEMMA, Grove, Breakout Garden and Gravity — the exact cable or adapter, with the voltage gotchas surfaced.

bus · check
◖ I have
by Adafruit · 3v3-5v
◗ I want to connect
by SparkFun · 3v3
My host's logic runs at
!Check first
Plugs in directly — but mind your host's voltage.

STEMMA QT and Qwiic share the same JST-SH connector, so they mate directly. Grab a standard cable and confirm each breakout's pinout is i2c. Qwiic is 3.3 V only — if your host runs 5 V logic, add a level shifter or you may damage it.

STEMMA QT cableJST-SH 4-pinShop →JST-SH cable kitassorted-length pack — for chaining several boardsShop →i2c level shifter (3.3 V ↔ 5 V)add if host is 5 VShop →

What it's checking

What i2c connector compatibility really depends on

Do the plugs mate? Same housing and pitch means a stock cable works — that's why Qwiic and STEMMA QT are one ecosystem in practice. Different housings mean an adapter.

Do the pinouts agree? The dangerous case isn't a plug that won't fit, it's one that fits while disagreeing about which conductor is SDA. i2c won't warn you: the bus goes silent, or power meets a data line. See any two orders side by side in the pinout visualizer.

Do the voltages match? The one that costs money. i2c has no negotiation — whatever the host drives reaches every device. A 3.3 V-only board on a 5 V host needs a level shifter, and no adapter substitutes for one. That's the warning this tool surfaces before you plug anything in.

Bridged, it's an ordinary bus again: unique addresses (conflicts have fixes), pull-ups in parallel, and a 400 pF budget over the whole run. If nothing answers once connected, an i2c scan separates a cable fault from an address clash immediately.

Prefer to browse?

Every pairing is also pre-answered as its own page — see the full compatibility index, or jump to a connector standard for its pinout and specs. Starting fresh instead of bridging? Which connector? picks one for you.