When designing a system using Grove, in particular, the issue of capacitance comes into consideration. The I2C specification lists a maximum of 400 pF over the I2C bus as a whole, taking connected devices, PCB’s and wiring into account.
The Grove cables come in various types, some are ribbon cable, others are individual wires.
Seeed do not seem to care about the size of conductors or the amount of capacitance, but to help customers I suggest that the capacitance data needs to be available.
Typically for ribbon cable, capacitance might vary between 14 - 50 pF per metre. For individual wires, the capacitance will be different if the 4 wires in the cable are bound together using shrink tubing or cable ties. The main variable is the insulating material, again, this is not specified by Seeed.
For a big system with lots of sensors, Lead capacitance can add up, and it can affect maximum bus speed.
Isn’t it about time this data was made available to customers ?
While I am on this tack, Seeed make a lot of Grove sensors actuators and the like, that connect to I2C. Surely its possible to consistently specify the I2C address (range) and the value of I2C pullups that are integrated into the chip or included on the PCB; also what maximum bus speed is supported. Its a real pain to have to refer to manufacturers data to get this information, as it is often buried deep.