I2C is a really useful protocol for connecting parts to your microcontroller. It’s well-supported by the majority of different microcontrollers and languages, it only uses two pins (plus power and ground), and you an connect many devices to a single I2C bus. To make it even easier, some hardware manufacturers are putting push-fit connectors on their products, so you can build an electronics project by just slotting connectors into holes – no soldering necessary….
STEMMA (by Adafruit) is physically slightly different to Grove, but it is close enough that it plugs in. Unlike Grove, all STEMMA 4-pin connectors are I2C. Microcontrollers may send 3 V or 5 V down the power line, but all STEMMA devices can accept either 3 V or 5 V, so any 4-pin STEMMA device should be I2C, and compatible with any 4-pin STEMMA microcontroller port.
STEMMA QT is, simply, STEMMA shrunk down to 1 mm-spaced pins. The QT version is compatible with STEMMA, but you need a conversion cable to click everything into place.
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