The Pi-Connect Lite is a HAT addon board for the Raspberry Pi 2/3/4/5/Zero(2,W) that allows easy and reliable interfacing with popular flight controllers used in unmanned vehicles.

It removes the complexity and risk of wiring up the telemetry and power connectors between the Pi and the vehicle systems.

It has been designed with reliability and a small form factor at the forefront, allowing for it to be used in both the smallest and largest of vehicles.

The Pi-Connect features:

• High current power supply
  • Wide input voltage (7 - 30V)
  • Reverse input protection
  • ESD protected
  • Supplies a full 5.1V at 3.5A for the Pi and accessories
  • Overcurrent protection
  • Short circuit protection
  • Low EMI
• 2x Telemetry (UART) ports using a JST-GH 6-pin Dronecode standard connector

The board also features a power button which safely switches off the Pi via issuing a shutdown signal. This ensures the Pi is cleanly shutdown and reduces the risk of system corruption.

The 2.X series has a major re-design, using a different power conversion setup and additional features. This includes:

• Power connector changed to XT30
• Power switch changed to power button
• Lower EMI/EMC
• Additional JST-GH telemetry port

The Pi-Connect requires the following equipment:

• Power source of 7-30V, capable of supplying at least 15W
• Raspberry Pi 2B, 3B, 4, Zero, Zero W, Zero2 running the Raspian or Ubuntu OS.
• Flight controller running Ardupilot/PX4. A telemetry cable with a JST-GH plug is needed to plug into the Pi-Connect. Cables with JST-GH/JST-GH and DF13/JST-GH plugs are available on the webstore.

The Pi-Connect Lite is compliant with the following standards:

• Raspberry Pi uHat standard
• Pixhawk connector standard
• RoHS

It is designed to meet CISPR22 Part B EMC standard

The power supply is based on the AP64501 DC/DC converter.

The Pi-Connect's power input in an XT30 connector. These are readily available from many RC and electronics stores.

Next the board should be mounted onto the Pi's 40-pin connector such that the telemetry and power connectors face towards the interior of the Pi.

The telemetry connector should be connected to the flight controller. The pinout of the JST-GH connector allows for direct connection to the flight controller without any crossover cables required.

Some configuration is required to configure the power switch actions and serial port.

A reboot will be required for the changes to take effect.

Insert the following text into /boot/config.txt:

# Power switch
dtoverlay=gpio-shutdown,gpio_pin=4
dtoverlay=gpio-poweroff

# Extra UART
dtoverlay=uart4,ctsrts    # Pi4 only
dtoverlay=uart3-pi5,ctsrts  # Pi5 only

Then run the following command to enable the UART port if not running on a Pi 5:

sudo raspi-config nonint do_serial 2

On a Pi 5, instead insert the following text into /boot/firmware/config.txt:

dtparam=uart0=on

In /boot/firmware/syscfg.txt, modify the line dtparam=i2c_arm=on to dtparam=i2c_arm=off.

Insert the following text into /boot/firmware/usercfg.txt:

# Power switch
dtoverlay=gpio-shutdown,gpio_pin=4
dtoverlay=gpio-poweroff

# Extra UART
dtoverlay=uart4,ctsrts

In /boot/firmware/config.txt, modify the line dtparam=i2c_arm=on to dtparam=i2c_arm=off.

Insert the following text into /boot/firmware/config.txt:

# Power switch
dtoverlay=gpio-shutdown,gpio_pin=4
dtoverlay=gpio-poweroff

# Extra UART
dtoverlay=uart4,ctsrts

The power button performs a safe software shutdown of the Raspberry Pi before cutting power. The button can be internal (the default, on board) or external (off board).

A long-push of the button (V2.1 board or later) will force power off. The button must be pushed for at least 6 seconds. Any button pushes within 5.5 seconds of board power-up will be ignored.

Fitting an external button is useful in cases where the Pi-Connect is mounted in a difficult-to-reach location. A button can instead to mounted in a better location and then wired to the external button port on the Pi-Connect Lite.

If an external power button is desired, ensure the button is connected to the Ext Switch ports on the Pi-Connect Lite board and the Int|Ext trace is cut on the Int side and soldered on the Ext side.

The button must be a momentary button.

To restore the functionality of the internal button, restore the cut/solder of the Int|Ext to the original state.

The first UART is identified as /dev/serial0, or /dev/ttyAMA0 on the Pi 5:

Pin 1 is on the left-hand side when looking at the top of the board.

The second UART is identified as /dev/ttyAMAx, where x is a number determined by the OS configuration.

Pin 1 is on the left-hand side when looking at the top of the board.

The Pi-Connect uses the following Pins on the 40-pin header of the Raspberry Pi:

(This does not include the ground pins, all of which are connected to the Pi-Connect board)

The following is a changelog of the hardware revisions of the Pi-Connect Lite. The revision numbers are printed on the top side of the board.

• Changed to smaller (standard) 40-pin header
• Button long-push forces off power

Initial Release