Quick Answer
Most Pixhawk-standard boards use small JST-GH connectors in a few common sizes for TELEM, GPS, CAN and I2C ports. Each port has a fixed pin order, so plugging a cable in backward or into the wrong port can damage a device. Learning the standard pinouts and buying or making the right cable is most of the battle.
Why JST-GH?
JST-GH is a small connector type with a locking tab, chosen for Pixhawk-standard boards because it is compact, holds a firm connection under vibration, and comes in several pin counts. You will see the same connector family used for GPS units, telemetry radios, power modules, and CAN devices, just with different pin counts depending on how much data each port carries.
Because the connector is standard, cables made for one Pixhawk-standard board will usually fit another, as long as the port carries the same signals in the same order. This is a big part of why the Pixhawk ecosystem is easy to mix and match between brands.
Common Pin Counts and What They Carry
- 4-pin: Common for I2C devices, like some compass or LED modules, carrying power, ground, and two data lines.
- 6-pin: A common size for GPS modules, which need power, ground, and separate data lines for GPS and compass information.
- 8-pin: Often used for a combined GPS and safety switch connection on some boards.
- 2-pin and 3-pin: Used for simple power connections and some sensor inputs.
The exact pin count you need depends on the specific port and device, so always check your flight controller's own documentation diagram rather than assuming based on pin count alone. Two 6-pin cables can carry completely different signals if they connect to different port types.
TELEM Ports
TELEM ports are general-purpose serial ports, most often used for telemetry radios that send flight data back to your ground station, but also used for GPS modules, companion computers, and other serial devices. Most Pixhawk-standard boards have at least two TELEM ports, and larger boards have more.
Each TELEM port needs to be told what protocol to expect in the flight controller's software, since the port itself is just a generic serial connection. Setting the wrong protocol on a TELEM port is a common cause of a telemetry radio or GPS that seems to be wired correctly but does not work.
GPS Ports
GPS ports typically carry both GPS data and compass data on the same cable, since most GPS modules include a built-in compass. This is usually a 6-pin or similar connector, wired so that power, ground, GPS serial data, and compass data all travel together.
If your board has two GPS ports, the second is often meant for a backup or second GPS unit, which can improve reliability on a mapping or long-range aircraft. Setting up GPS wiring correctly is covered in more detail in adding GPS to your drone.
CAN Ports
CAN ports carry DroneCAN data, a shared bus that can serve many devices, such as GPS modules, power monitors, and some ESCs, over just two data wires plus power and ground. Most Pixhawk-standard boards have at least one CAN port, and larger boards often have two, which lets you separate devices onto different bus segments if needed.
Wiring for CAN is more forgiving than some other ports, since devices on the bus do not each need a dedicated physical port on the flight controller. To understand how CAN devices actually communicate compared to older wiring methods, read DroneCAN vs PWM.
I2C Ports
I2C ports carry a simple, slower data protocol used for smaller add-on devices, such as some compasses, airspeed sensors, and rangefinders. I2C can support multiple devices on one bus, similar in spirit to CAN but generally used for lower-speed, less critical sensors.
I2C wiring is sensitive to cable length and electrical noise, so keep I2C cable runs short and away from power wiring where you can, especially on larger aircraft with long cable runs.
Making or Buying Cables
You can buy pre-made JST-GH cables in standard lengths for most common ports, which is the simplest option for most builders. If you need a custom length or a specific pinout, you can also crimp your own cables using a JST-GH crimping tool, the correct pins, and the connector housings.
When making your own cables, always check pin order carefully against the flight controller's documentation before crimping. A single reversed pin can damage a sensor or, worse, a power port. If in doubt, buy a pre-made cable for a critical connection like power.
Avoiding Common Wiring Mistakes
- Do not force a connector into place if it does not slide in easily. This usually means it is the wrong size or backward.
- Never assume two connectors with the same pin count carry the same signals.
- Double-check polarity on any power connection before plugging it in, especially on homemade cables.
- Keep a small paper or digital diagram of your specific board's port layout, since it saves time on future repairs.