Editing I²C (section)

==Connectors==
===TRRS===
A '''TRRS''' plug is a type of 3.5 mm phone connector used by many split ergonomic keyboards as interconnect.
It is not considered very reliable for digital signals, but is inexpensive, common and relatively small.

"TRRS" stands for "Tip-Ring-Ring-Sleeve", indicating that is has four contacts.
It was defined in the Japanese standard JEITA/EIAJ RC-5325A, "4-Pole miniature concentric plugs and jacks", originally published in 1993.

{|class="wikitable"
|-
! Keyboard !! Tip !! Ring !! Ring !! Sleeve
|-
| [[ErgoDox]] || SDA || SCLK || Vcc || GND
|-
| [[Lily58]] || Vcc || GND || SDA || SCLK
|-
|}

===JST SH, JST PH and Grove===
Several vendors of microcontroller and sensor boards have made mostly-compatible cabling systems  for connecting them with I²C and power without requiring soldering.
A number of cables and adaptor cables are available with different connectors.

Sparkfun's '''Qwiic''' uses compact four-pin JST SH connectors, always for I²C. Voltage is 3.3V.

Seeed Studio's '''Grove''' uses four-pin JST PH-''like'' connectors for various purposes, of which some boards use them for I²C. The first two pins are always for power (3.3V '''or''' 5V)  with the other two for signals.

Adafruit's '''STEMMA''' system uses four-pin JST PH connectors, always for I²C, and the connectors are similar enough so at to fit those used by Grove in either direction.<br />
'''STEMMA QT''' uses the compact four-pin JST SH-connectors, in compatible pinout with Qwiic.
However, STEMMA and STEMMA QT allow voltages between 3 and 5V, like Grove.
The system also contains three-pin JST PH connectors for other purposes.

Note that Sparkfun Qwiic is always 3.3V, but the others use either 3.3V or 5V.
STEMMA boards from Adafruit are supposed to work with the full range of 3-5V.

Cables are coloured:
{|class="wikitable"
|-
! Pin !! Qwiic/STEMMA QT !! STEMMA !! Grove !! Use
|-
| 1 || Black || Black || Black || GND
|-
| 2 || Red || Red || Red || VCC
|-
| 3 || Blue || White || White || SDA
|-
| 4 || Yellow || Green || Yellow || SCL
|}