Qwiic, Stemma (3P/4P/QT), Breakout Garden, Grove I2C Adapter
One fabulous I2C quick connect adapter to rule them all! The quick connect adapter combines the most popular I2C breakout standards in one Bus Pirate compatible plank.
I2C is a simple communication protocol used by many sensors and devices. Over the years, manufacturers created “standard” I2C breakout board connectors for quick solder-free prototyping. All have the same basic four connections: power (V+), ground (GND), I2C Serial Data (SDA), and I2C Serial Clock (SCL). However, the pinout and connector types vary.
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I2C Breakout Standards
- Adafruit Industries: Stemma 3P, Stemma 4P (I2C), Stemma QT
- SparkFun Electronics: Qwiic
- Seeed Studio: Grove
- DFRobot: Gravity
- Pimoroni: Breakout Garden
Adafruit’s Stemma 3P is a single signal connector, not an I2C connector.
Pinout Table
| Pin | Stemma 3P | Stemma 4P | Stemma QT | Qwiic | Grove | Gravity | Breakout Garden |
|---|---|---|---|---|---|---|---|
| 1 | SIGNAL | SCL | GND | GND | GND | SDA | V+ |
| 2 | V+ | SDA | V+ | V+ | V+ | SCL | SDA |
| 3 | GND | VOUT | SDA | SDA | SDA | GND | SCL |
| 4 | – | GND | SCL | SCL | SCL | V+ | INT |
| 5 | – | – | – | – | – | – | GND |
Breakout Garden is a dual row PCB edge connector. The connections on each side are mirrored so boards can be inserted in both directions. The table above shows the pinout for a single row on one side.
Connector Types
| Standard | Connector | Pitch | Example Part Number |
|---|---|---|---|
| Stemma 3P | JST PH 3P | 2.0mm | JST: S3B-PH-SM4-TB, Generic: HC-PH-3AWT |
| Stemma 4P | JST PH 4P | 2.0mm | JST: S4B-PH-SM4-TB, Generic: HC-PH-4AWT |
| Stemma QT | JST SH 4P | 1.0mm | JST: SM04B-SRSS-TB, Generic: HC-1.0-4PWT |
| Qwiic | JST SH 4P | 1.0mm | JST: SM04B-SRSS-TB, Generic: HC-1.0-4PWT |
| Grove | “HY” 4P | 2.0mm | HY-4P, HY2.0-4P-SMD, A2008WR-S-4P |
| Gravity | JST PH 4P | 2.0mm | JST: S4B-PH-SM4-TB, Generic: HC-PH-4AWT |
| Breakout Garden | PCB edge slot conn. 2 x 5P | 2.54mm | ED10BGFBK |
Thanks!
A huge thank you to Funcan, kd7eir, grymoire, and henrygab for testing the various connectors with genuine breakout boards!
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