#Coding4Fun – How to control your #drone with 20 lines of code! (5/N)

Coding4Fun Drone 🚁 posts

Hi!

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.

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

As you can read, all the information is condensed in a single line and we can split and get:

pitch
roll
yaw
vgx
vgv
vgz
templ (temperature low)
temph (temperature high)
tof (time of flight)
h (height)
b (battery)
baro (barometer)
time
agx
agy
agz

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[21]
'39'
>>>

So with this, to get the battery level of the drone will require this code:

	# Bruno Capuano
	# get drone battery demo

	import socket
	import time
	import threading

	def sendCommand(command):
	global response
	timestamp = int(time.time() * 1000)

	clientSocket.sendto(command.encode('utf-8'), address)

	while response is None:
	if (time.time() * 1000) – timestamp > 5 * 1000:
	return False

	return response


	def sendReadCommand(command):
	response = sendCommand(command)
	try:
	response = str(response)
	except:
	pass
	return response

	def sendControlCommand(command):
	response = None
	for i in range(0, 5):
	response = sendCommand(command)
	if response == 'OK' or response == 'ok':
	return True

	return False

	def receiveData():
	global response
	while True:
	try:
	response, _ = clientSocket.recvfrom(1024)
	except:
	break

	def readStates():
	global battery
	while True:
	try:
	response_state, _ = stateSocket.recvfrom(256)
	if response_state != 'ok':
	response_state = response_state.decode('ASCII')
	list = response_state.replace(';', ':').split(':')
	battery = int(list[21])
	except:
	break

	# ———————————————–
	# Main program
	# ———————————————–

	# connection info
	UDP_IP = '192.168.10.1'
	UDP_PORT = 8889
	last_received_command = time.time()
	STATE_UDP_PORT = 8890

	address = (UDP_IP, UDP_PORT)
	response = None
	response_state = None

	clientSocket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
	clientSocket.bind(('', UDP_PORT))
	stateSocket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
	stateSocket.bind(('', STATE_UDP_PORT))

	# start threads
	recThread = threading.Thread(target=receiveData)
	recThread.daemon = True
	recThread.start()

	stateThread = threading.Thread(target=readStates)
	stateThread.daemon = True
	stateThread.start()

	# drone information
	battery = 0

	# connect to drone
	sendControlCommand("command")

	# get and display battery
	sendReadCommand('battery?')

	time.sleep(5)
	print(f'Battery: {battery} %')

view raw DjiTelloGetBattery.py hosted with ❤ by GitHub

The output is not very amazing, but it works!

powershell console displaying the drone battery level.

Happy coding!

Greetings

El Bruno

#Coding4Fun – How to control your #drone with 20 lines of code! (5/N)

Coding4Fun Drone 🚁 posts

Reading drone information

References

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Coding4Fun Drone 🚁 posts

Reading drone information

References

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