Tello project

This repository contains university project. We have based our idea on repository of easyTello on GitHub. We have created project to control a Tello drone by special QR codes which contains a special mission for UAV. Warning! We wrote code on Linux operating system! We haven’t tested code in other platforms so maybe not every feature will have worked correctly on your computer.

Installation

TelloBird uses Python 3 and OpenCV with dev-kits, which is necessary to read QR code. Communication with drone is based on UDP protocol and special commands, which are described in DJI Tello SDK documentation. Don’t use:

pip3 install opencv-python

This installation wouldn’t install all necessary modules. We suggest to use for example this tutorial for installing openCV. To communicate with drone, you have to have socket and threading modules, which should be installed with Python by default. Unless they are installed, you have to use:

pip3 install socket threading

All communiaction tasks are solved by easyTello module.

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Extended module, TelloBird

We have extended easyTello modules by adding our module TelloBird which contains our protocols of missions. Every mission is triggered by QR code, which is exclusive for each task.

Features

We have defined a list with all available missions and states of UAV:

class TelloBird(Tello):
    ...
    listOfStates = ["landed", "in-air", "moving", "turning", "too-weak"]
    listOfMissions = ["basicMisssionL", "squareMissionL", "squareMissionT", "takeOffMission", "circleMissionL","eightMissionL","circleCurveMissionL", "test"]
    ...

List of states provides security that we will not be able to run a mission which requires different starting state. For example, we will not able rerun takeOffMission because the drone will already have set a state in-air. The last letter in name of a mission says on state of drone:

• L - it means that drone is landed
• T - it means that drone is in air

Some of them need to be run with kind of argument. For example, squareMissionL requires an argument how far UAV has to fly forward. To run properly function you have to create a QR code as string as in the pattern:

_squareMissionL_ 30

Warning!! Remember, drone has own tolerance of distance. The minimum value which you can pass to command is 20 In other hand takeOffMission does not need extra argument but every validation of passing mission is checked by the special function:

    def __validadtionCommand__(self, commands):
        if len(commands) > 1:
            return commands
        commands.append("None")
        return commands

Next mission, which we have added, is watingForMission.

    def watingForMission(self):
        if self.statusOfMission == True:
            return 0
        if self.last_frame is not None:
            data, self.bbox, straigt_qrcode = self.detector.detectAndDecode(self.last_frame)
        if self.bbox is not None:
            print(data)
            if data != "":
                commands = self.__validadtionCommand__(data.split())
                index = self.listOfMissions.index(commands[0])
                self.statusOfMission = True
                self.startMission(index, commands[1])
        self.bbox = None

It provides all features which are necessary to read QR codes and run proper mission. Firstly, the method check if drone is able to run mission. This is not the most important thing but if you will write async function, it becomes needful. In startMission code runs a specific function:

    def startMission(self, chooseMission: int, parametr):
        if chooseMission == 0:
            self.wait(int(self.minimalTimeWaiting*0.75))
            self.basicMisssionL()
        elif chooseMission == 1:
            self.wait(int(self.minimalTimeWaiting*0.75))
            self.squareMissionL(parametr)
        elif chooseMission == 2:
            self.wait(int(self.minimalTimeWaiting*0.75))
            self.squareMissionT(parametr)
        elif chooseMission == 3:
            self.wait(int(self.minimalTimeWaiting*0.75))
            self.takeOffMission()
        elif chooseMission == 4:
            self.wait(int(self.minimalTimeWaiting*0.75))
            self.test(parametr)

You can see that we have implemented simply switch case method. Code checks which function has to be executed. Every mission is defined in module. For example:

    def takeOffMission(self):
        if self.currentState == self.listOfStates[0]:
            self.takeoff()
            self.wait(self.minimalTimeWaiting)
            self.currentState = self.listOfStates[1]
            self.__endingMission__()
        else:
            self.__endingMission__()
            return 0

The endingMission provides resetting all variables which are essential to run the next mission.

We add a function that saves all logs into a CSV file. It writes for example:

Id,Command,Response,Start_time,End_time,Duration
0,command,b'ok',2022-01-31 15:57:43.856717,2022-01-31 15:57:43.917605,0.060888
1,wait,,2022-01-31 15:57:43.917711,,
2,land,b'error',2022-01-31 15:57:46.920994,2022-01-31 15:57:46.937990,0.016996
.
.
.

The function is executed always after shutting down a script's process.

Contributing

Pull requests are welcome. For major changes, please open an issue first to discuss what you would like to change.

Please make sure to update tests as appropriate.

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License

Copyright (c) 2021 Arkadiusz Kruszynki Maciej Zawadzki

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

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FAQ

1. Problems with H.264 decoder.

non-existing PPS 0 referenced
decode_slice_header error
non-existing PPS 0 referenced
decode_slice_header error
no frame!

This error is easy to solve. Packages of information from UAV come with big delay. You have to only wait some time. On the other hand we have managed with this problem and IDE stopped executing program. We suggest changing an IDE.

no h264 decode

This problem is critical. Some cases you will not able to run this code in macOS or windows. On Linux you will have to install special libraries for lib264.

2. Responses from UAV

Response: error 'no imu' 

This problem is very complex. Firstly, you have to check state of drone's battery. It must not be too low. Secondly, you have to make calibration in Tello app. Thirdly, you would have to send commands to drone too quickly. You need to increase delay between commands. Moreover, sometimes the environment in which drone is tested, causes this problem. You have to check if lights in room is enough for drone and the base, from which done take off, is enough colourful. REMEMBER! Drone uses its camera for stabilization and IMU.