Gopro control from FC with companion computer.

I am making some drone boats. As usual drone users, I also want to take pictures on the boat. I think GoPro camera is very popular. But I have never seen using Gopro on the drone boat. Then I make a solution. Building this system is not easy for me. Then I'd like to share my experiences with Ardupilot folks.

Please see following high level chart.

1. GCS or Transmitter send "camera trigger". Flight Controller raise signal at AUX OUT pin.
2. Companion Computer(Raspberry Pi) watch AUX OUT. When getting signal, Raspberry pi send a shutter command to GoPro via Wifi.
3. WiFi antenna is reached to GoPro. GoPro can get signal even if in the sea.

GoPro is not only very popular but program interface via USB, WiFi and Bluetooth. We can find GoPro API at here

When thinking under the water environment, we can use great GoPro protection case. Then we don't want to use USB cable nor don't want to use weak Bluetooth. The following discussion is just only focus on WiFi.

What we want to do is like this illustration. {: align="center"}

Usually, we say that radio waves cannot transmit through water. It is not strictly correct. radio waves decay rapidly in water. When you attach antenna closely GoPro, you can use wifi.

First of all, we must find WiFi USB dongle with antenna connector. Because it is very hard to add antenna on the Raspberry Pi board and that WiFi power is weak. I find USB WiFi dongle with screw antenna. And you find 1m coaxial cable with SMA-P connector.

Depending on cable connector, you may need gender change connector.

At the cable opposite side, make an antenna for wifi. Wifi 2.5GHz wave length is about 12 cm. Then the antenna length should be 6cm (1/2 wave length) or 3cm (1/4 wave length) Now strip off approx. 3cm. {: align="center"}

I put glue and cover by heat shrink tube for water resistant.

THe following process is supported by Raspbian OS 64bit

First of all, just connect USB WiFi dongle and see 'ifconfig' or 'ip a' command response. If your WiFi dongle is recognized as 'wlanx'. You are so lucky. Raspbian OS has adequate device driver. If your WiFi dongle does not work, you need to install device driver. You enter the command 'lsusb', you can find connected device characteristics. In my case, that is "Realtek Semiconductor Corp. RTL88x2bu".

Then I need to install RTL88x2bu device driver. (Unfortunately, I am not familiar with kernel compile. I introduce just only install scenario step by step)

1. sudo apt update

2. sudo apt upgrade

3. sudo apt install git bc dkms raspberrypi-kernel-headers

4. sudo apt update

5. sudo reboot

6. git clone https://github.com/cilynx/rtl88x2bu

7. cd rtl88x2bu/

8. sed -i 's/I386_PC = y/I386_PC = n/' Makefile

9. sed -i 's/ARM_RPI = n/ARM_RPI = y/' Makefile

10. VER=$(sed -n 's/\PACKAGE_VERSION="(.*)"/\1/p' dkms.conf)

11. sudo rsync -rvhP ./ /usr/src/rtl88x2bu-${VER}

12. sudo dkms add -m rtl88x2bu -v ${VER}

13. sudo dkms build -m rtl88x2bu -v ${VER}

14. sudo dkms install -m rtl88x2bu -v ${VER}

After finishing these process, you need reboot. You will find wlan0 and wlan1

To erase wlan0 (on board wifi) you make the following file.

filename: /etc/modprobe.d/raspi-blacklist.conf

#wifi
blacklist brcmfmac
blacklist brcmutil

And reboot.

Now you use USB WiFi dongle.

GoPro has API interface from 2021. It's called Open GoPro

When you use GoPro Wifi, first of all you start and connect QUIK from your smartphone and push "Preview" button. QUIK shows the window connect to GoPro with Access Point. You can get AP name and password from "Camera info" in "connect" menu. The most important thing is GoPro is Access Point. The Raspberry Pi should be client. Then you prepare GoPro AP in the Raspberry Pi.

pip is required.

sudo apt -y install python3-pip

And install

pip install open-gopro

Maybe you connect your Raspberry PI to your home WiFi router. The following steps connect your Raspberry pi to GoPro. You need to change WiFi connection. It means if you use SSH usually, it cannot be used. There are two solutions. One way is preparing physical HDMI display and wireless keyboard. Another way is using Ethernet adapter. If your Windows or Mac does not have Ethernet connector, you can prepare USB-Ethernet connector. It is relatively cheap and some connector supports Mac environment and Windows one.

I am using Ether net connector and both side IP address are static like 192.168.300.x. Setting is easy and you can find the way anywhere.

Please check contents in

/etc/wpa_supplicant/wpa_supplicant.conf

if you setup SSH, you will see the definition of current WiFi access point name. Anyway you add

network={
    ssid="Gopro Access Point Name"
    psk="password"
}

Reboot is required. After reboot finished, you can test wpa_cli command. wpa_cli has rich functions, but now we just only test list and set AP. When you want to list AP

wpa_cli -i wlan- list_networks

if you choose AP you want to connect

wpa_cli -i wlan- select_network x

x is the list number.

Of course this command can change connection, but if choosing AP can use or not is other discussion. After changing AP connection, please wait a few minutes. Check 'ifconfig' command if your Raspi is assigned ip address or not. GoPro will give you 10.5.5.x local ip address.

Try following simple program.

import requests
import time
import json

GOPRO_BASE_URL = "http://10.5.5.9:8080/"
cmd = GOPRO_BASE_URL+"/gopro/camera/presets/set_group?id=1001"
response = requests.get(cmd,timeout=10)
response_raise_for_status()
resp = response.json()
print( json.dumps(resp))

THis command make gopro enter into camera mode. When run this program and GoPro makes some noise. Maybe OK.

Now we set up Ardupilot. For sending shutter signal. You need to change parameter

CAM_TRIGG_TYPE=1

THis is in other words "Relay mode"

WHich pins should be shutter ? Usually, AUX OUT 5 or AUX OUT 6 are chosen.

These are SERVO13 or SERVO14. I choose AUX OUT5. Then parameter set as

RELAY_PIN=54

And Servo13 should be GPIO

SERVO13_FUNCTION=-1

Finally don't forget "Write parameters"

You can change shutter push duration. But we will pick up GPIO voltage up edge, duration is not so important.

FInally set Transmitter switch

RC6_OPTION=9

9 means Camera Trigger.

If you set all following above specifications. GPIO issue pulse when shutter is requested.

(2024/03) New Raspi OS(Bookworm) changed many components. Pi GPIO does not work anymore. I must change using GPIOzero.

We transfer Pixhawk signal to Raspberry via GPIO. This time, I choose GPIO26.

IO pin and GND should be connected like this.

THis program is watching GPIO26(TESTIO). If GPIO voltage is high, the interruption is brought up and 'callback1' routine is called.

Finally, the system is built.

Fix the antenna on the GoPro.

(This picture uses see through scotch tape for your understanding. Actually use water resistant tape.)

you can try final code gopro-fc.py

Needless to say, Python program runs on Raspberry Pi.

THis program generate another thread for sending KeepAlive signal to GoPro. If you don't send GoPro signal, GoPro might be go down sleep. Sending frequency should be changed by your environment. When starting this program, GoPro mode is changed into Camera and wait for Flight Controller signal. You can try Transmitter switch (6) or 'Shutter Trigger' in connected Mission Planner. GoPro camera shutter is triggered.

I make a holder by brass for avoiding rust.

Fix this one to the boat

THis is a sample picture.

I put here a standard procedure for your understanding.

• Power on Pixhawk and Raspberry PI.
• Connect to Mission Planner (Maybe via telemetry)
• Connect to Transmitter.
• Connect ether-net cable between PC and Raspi.
• Start up SSH with ether-net.
• Make sure boat status.
• Power on GoPro.
• Connect to QUIK and push "Preview botton"
• Connect to GoPro WiFi using wpa_cli command.
• Check ifconfig if assgined ip address by GoPro
• Start like gopro-fc.py script.
• Set Gopro on the boat.
• Start boat and run Survey mode on the Mission Planner.