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RPi CM4 Flash Guide

Steps taken to flash the CM4 board, boot it, and connect it to PX4

Please Note:

  • If you are using PX4, you will need to use PX4 1.13.1 or newer for PX4 to recognize this baseboard.
  • The fan does not indicate if the RPi CM4 is powered/running or not.
  • The power module plugged into Power1/2 does not power the RPi part. You can use the additional USB-C Cable from the PM03D power module to the CM4 Slave USB-C port.
  • The Micro-HDMI port is an output port.
  • Some RPi CM4 might not have Wifi device and therefore won’t connect automatically, unless you plug it into a router or a compatible Wifi dongle into the CM4 Host ports.

Flash EMMC

We need to flash a RPi image onto EMMC.
  1. 1.
    Switch Dip-Switch to RPI.
  2. 2.
    Connect computer to USB-C CM4 Slave port used power & flash the RPi.
  3. 3.
    Get usbboot, build it and run it.
sudo apt install libusb-1.0-0-dev
git clone --depth=1 https://github.com/raspberrypi/usbboot,
cd usbboot
make
sudo ./rpiboot
  • You can now install your favorite Linux distro, e.g. Raspberry Pi OS 64bit, using The rpi-imager. Make sure to add wifi and ssh settings (hidden behind the gear/advanced symbol).
sudo apt install rpi-imager
rpi-imager
  1. 1.
    Once done, unmount the volumes, and power off the CM4 by unplugging USB-C CM4 Slave.
  2. 2.
    Switch Dip-Switch back to EMMC.
  3. 3.
    Power on CM4 by providing power to USB-C CM4 Slave port.
  4. 4.
    To check if it’s booting/working, either check HDMI output, or connect via ssh (if set up in rpi-imager, and wifi is available).

Connect PX4 to CM4 via serial

Pixhawk 6X talks to CM4 using Telem2 (/dev/ttyS4).
  1. 1.
    To enable this MAVLink instance, set the params: - MAV_1_CONFIG: 102 - MAV_1_MODE: 2 - SER_TEL2_BAUD: 921600
  2. 2.
    reboot the FMU
  3. 3.
    On the RPi side, you can connect it to Wifi using a router or a Wifi Dongle.
  4. 4.
    Enable serial port to FMU by using raspi-config: Go to 3 Interface Options, then I6 Serial Port. Choose - login shell accessible over serial → No - serial port hardware enabledYes Finish, and reboot. (This will add enable_uart=1 to /boot/config.txt, and remove console=serial0,115200 from /boot/cmdline.txt
  5. 5.
    Now MAVLink traffic should be available on /dev/serial0 at a baudrate of 921600.

Try out MAVSDK-Python

  1. 1.
    Make sure the CM4 is connected to the internet, e.g. using a wifi, or ethernet.
  2. 2.
    Install MAVSDK Python:
python3 -m pip install mavsdk
  1. 1.
    Copy an example from the MAVSDK-Python examples.
  2. 2.
    Change the system_address="udp://:14540" to system_address="serial:///dev/serial0:921600"
  3. 3.
    Try out the example. Permission for the serial port should already be available through the dialout group.
You can also use your own power supply to power the RPi CM4 baseboard.