Grove is SeeedStudio's plug and play system, its the oldest/most established, initiated in 2010 as 'stem/twig' and then renamed Grove. There's only one type of cable and 4-pin connector, but it can have I2C/analog/digital/whatever on the cable. The cable/connector is proprietary, and sold only by Seeed (it seems).
- STEMMA 4-pin cables are cross-compatible with Grove parts. You can plug the larger 4-pin STEMMA cables/devices/controllers into Grove I2C devices/controllers just fine and vice-versa. Even though the connector they use is not the exact same part, the cables will fit into the connectors!
- STEMMA uses the same voltage as Grove - power is 3-5VDC and data is 3-5VDC with level shifting/regulators on devices.
- Some Grove devices use 4-pin connectors for non-I2C analog or digital data. STEMMA only uses I2C for the 4-pin connectors. You cannot use Grove analog/digital parts with STEMMA boards, stick to the I2C ones only!
To the left you can see two different Grove devices. The longer one to the left is a I2C device, you can see it has SCL/SDA marked next to the connector, and is compatible with STEMMA. The one to the right has SIG marked next to the connector, and is not compatible because its analog output, not I2C!
Below you can see the Grove cables, even though these are not JST PH they will work just fine with STEMMA 4-pin connectors