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

Buy Me A Coffee

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} %')

The output is not very amazing, but it works!

powershell console displaying the drone battery level.

Happy coding!

Greetings

El Bruno

References

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