Pi-Connect Lite

The Pi-Connect Lite is a HAT addon board for the Raspberry Pi 2B/3B/4/Zero(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 3A for the Pi and accessories
    • Overcurrent protection
    • Short circuit protection
    • Low EMI (Version 1.2+)
  • 1x Telemetry (serial) port using a JST-GH 6-pin Dronecode standard connector

The board also features a power switch 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 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 running the Raspian 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.
Specification Value Notes
Operating Temperature -25° - 70° C

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

Specification Value Notes
Absolute maximum input voltage 30V Exceeding this voltage may damage the Pi-Connect
Maximum input voltage 7V The Pi-Connect may work below this input voltage, but it is not guaranteed
Output voltage variation (Vpp) 0.35V Variation is larger at higher input voltages
Efficiency (30V input) >84%
Efficiency (18V input) >90%
Power dissipated (max) 2.5W

The power supply is based on the TPS54360 (or TPS54360B in Version 1.2+) DC/DC converter.

The Pi-Connect's power input needs to be soldered to the appropriate power source. The cables can be either soldered directly to the board, or the Power Cable Set can be soldered for a removable cable.

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.

Raspian

For ease of use, download and run this script.

Otherwise, insert the following text into /boot/config.txt:

# Power switch
dtoverlay=gpio-shutdown
dtoverlay=gpio-poweroff

Then run the following command to enable the serial port:

sudo raspi-config nonint do_serial 2

Ubuntu

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
dtoverlay=gpio-poweroff

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

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

If an external power switch is desired, ensure the switch 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 switch must be of a latching type with the centre pin common, like these switches.

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

In the Raspian OS, the UART is identified as /dev/serial0:

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

Pin Function
1 NC
2 Pi Rx
3 Pi Tx
4 NC
5 NC
6 Ground

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

Pin Alt Name Function
2 +5V
4 +5V
5 GPIO3 Power Switch
8 GPIO14 Pi Serial Tx
10 GPIO15 Pi Serial Rx
27 EEPROM
28 EEPROM
37 GPIO26 Power Switch

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

The power port is a 2-pin Molex Nano-fit. The connector is Molex part number 1054301102 and corresponding plug is Molex part number 1053071202.

More information about the Nano-fit product family can be found at the Molex website.

Note that it is not necessary to install any additional software to get the Pi-Connect working.

The following packages are ready-to-go for new users or those who want a ready-made solution:

Versions

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 TPS54360B power converter, as TPS54360 is end-of-life
  • Added EMC filter designed to meet CISPR22B EMC standard
  • RoHS compliant
  • Added ESD protection for power switch
  • Added 5.1V power output port

  • Swapped locations of the telemetry port and power switch
  • Better spacing layout of power supply components to simplify manufacturing
  • Added text labels to components
  • Added capacitor to power switch

Initial Release

Issue Affected Boards Resolution
Power switch does not work after enabling I2C All Disable I2C
External switch does not work when used with long cable V1.0 Add a 0.1uF capacitor between ground and GPIO3
The shutdown command sudo shutdown does not work All Use the physical switch on the Pi-Connect to shut down the Pi
  • products/pi-connect-lite.txt
  • Last modified: 2020/11/08 15:40
  • by stephen