Coding4Fun Drone posts
- Introduction to DJI Tello
- Analyzing Python samples code from the official SDK
- Drone Hello World ! Takeoff and land
- Tips to connect to Drone WiFi in Windows 10
- Reading data from the Drone, Get battery level
- Sample for real time data read, Get Accelerometer data
- How the drone camera video feed works, using FFMPEG to display the feed
- Open the drone camera video feed using OpenCV
- Performance and OpenCV, measuring FPS
- Detect faces using the drone camera
- Detect a banana and land!
- Flip when a face is detected!
Today is code time! In my previous post I share some code to send commands to the drone. Today I’ll show how to read the information from the drone. Before I start, someone asked if my kids are having fun with the drone. A image will be enough to answer this.
Reading drone information
So, as far as I understand, the drone is constantly sending information to the connected client. That’s why we have the following function running all the time in a separate thread:
def receiveData(): global response while True: try: response, _ = clientSocket.recvfrom(1024) except: break # ... more code response = None recThread = threading.Thread(target=receiveData) recThread.daemon = True recThread.start()
The response is stored in a global variable named response. And it’s very easy to understand the information that we the drone sends back. This is a sample received data.
As you can read, all the information is condensed in a single line and we can split and get:
- templ (temperature low)
- temph (temperature high)
- tof (time of flight)
- h (height)
- b (battery)
- baro (barometer)
In python this is a simple routine, and after split this into a list, the battery value is on index 21:
ls = 'pitch:0;roll:1;yaw:0;vgx:0;vgy:0;vgz:0;templ:79;temph:82;tof:10;h:0;bat:39;baro:50.42;time:0;agx:-8.00;agy:-17.00;agz:-999.00' >>> ls1 = ls.replace(';', ':').split(':') >>> ls1 ['pitch', '0', 'roll', '1', 'yaw', '0', 'vgx', '0', 'vgy', '0', 'vgz', '0', 'templ', '79', 'temph', '82', 'tof', '10', 'h', '0', 'bat', '39', 'baro', '50.42', 'time', '0', 'agx', '-8.00', 'agy', '-17.00', 'agz', '-999.00'] >>> ls1 '39' >>>
So with this, to get the battery level of the drone will require this code:
The output is not very amazing, but it works!