Assign data from drones to variables while using swarm lib and lamda function

[Morgens2]

Hi there!
I am working on a project using 2 crazyflie drones and the lighthouse V2 positioning system. I 've managed to print each drone's data (position, velocity etc.) through the lamda function. Now, I want to assign each drone's data to variables, in order to use them in my script. For example;

Variable	Corresponding data
X_1	the position of the 1st crazyflie on the x axis
X_2	the position of the 2nd crazyflie on the x axis
VX_1	the velocity of the 1st crazyflie on the x axis
VX_2	the velocity of the 2nd crazyflie on the x axis

Is this data already stored somewhere as a variable? And if so, how can I call/use it?
If not, what changes does my code need in order to achive that?
Can someone please help me it figure out? Thank you in advance.

Here is the code I use for printing each drone's data.

def run_shared_sequence(scf):

    box_size = 0.5
    flight_time = 2

    commander = scf.cf.high_level_commander

    commander.takeoff(0.6, 2.0)
    time.sleep(3)

    commander.go_to(box_size, 0, 0, 0, flight_time, relative=True)
    time.sleep(flight_time)

    commander.go_to(0, box_size, 0, 0, flight_time, relative=True)
    time.sleep(flight_time)

    commander.go_to(-box_size, 0, 0, 0, flight_time, relative=True)
    time.sleep(flight_time)

    commander.go_to(0, -box_size, 0, 0, flight_time, relative=True)
    time.sleep(flight_time)

    commander.land(0.0, 2.0)
    time.sleep(2)

    commander.stop()
    
def Position_callback(uri, timestamp, data, logconf):

    X = data['stateEstimate.x']
    Y = data['stateEstimate.y']
    Z = data['stateEstimate.z']

    print('{}, Position, x:  , {:.4f} ,  y:  , {:.4f} ,  z:  , {:.4f} ,'.format(uri, x, y, z), end = " " )

def PosTarget_callback(uri, timestamp, data, logconf):

    Targ_x = data['posCtl.targetX']
    Targ_y = data['posCtl.targetY']
    Targ_z = data['posCtl.targetZ']
    
    print(' Pos_Target, Cx:  , {:.4f}  , Cy:  , {:.4f}  , Cz:  ,  {:.4f} ,'.format(Targ_x, Targ_y, Targ_z), end = " ")   
    
def Velocity_callback(uri, timestamp, data, logconf):

    Vx = data['stateEstimate.vx']
    Vy = data['stateEstimate.vy']
    Vz = data['stateEstimate.vz']

    print(' Velocity, Vx:  , {:.6f} ,  Vy:  , {:.6f} ,  Vz:  , {:.6f} ,'.format(Vx, Vy, Vz), end = " " )
    
def VelTarget_callback(uri, timestamp, data, logconf):

    Targ_Vx = data['posCtl.targetVX']
    Targ_Vy = data['posCtl.targetVY']
    Targ_Vz = data['posCtl.targetVZ']

    print(' Vel_Target, CVx:  , {:.6f} ,  CVy:  , {:.6f} ,  CVz:  , {:.6f} ,'.format(Targ_Vx, Targ_Vy, Targ_Vz))
    
    
def start_position_printing(scf):
    uri = scf.cf.link_uri
    log_conf1 = LogConfig(name='Position', period_in_ms=200)
    log_conf1.add_variable('stateEstimate.x', 'float')
    log_conf1.add_variable('stateEstimate.y', 'float')
    log_conf1.add_variable('stateEstimate.z', 'float')    
    
    log_conf2 = LogConfig(name='Position_Target', period_in_ms=200)
    log_conf2.add_variable('posCtl.targetX', 'float')
    log_conf2.add_variable('posCtl.targetY', 'float')
    log_conf2.add_variable('posCtl.targetZ', 'float')
        
    log_conf3 =  LogConfig(name='Velocity', period_in_ms=200)
    log_conf3.add_variable('stateEstimate.vx', 'float')
    log_conf3.add_variable('stateEstimate.vy', 'float')
    log_conf3.add_variable('stateEstimate.vz', 'float')
    
    log_conf4 =  LogConfig(name='Velocity_Target', period_in_ms=200)
    log_conf4.add_variable('posCtl.targetVX', 'float')
    log_conf4.add_variable('posCtl.targetVY', 'float')
    log_conf4.add_variable('posCtl.targetVZ', 'float')


    scf.cf.log.add_config(log_conf1)
    scf.cf.log.add_config(log_conf2)
    scf.cf.log.add_config(log_conf3)
    scf.cf.log.add_config(log_conf4)

    
    log_conf1.data_received_cb.add_callback( lambda timestamp, data, logconf: Position_callback(scf.cf.link_uri, timestamp, data, logconf))
    log_conf2.data_received_cb.add_callback( lambda timestamp, data, logconf: PosTarget_callback(scf.cf.link_uri, timestamp, data, logconf))
    log_conf3.data_received_cb.add_callback( lambda timestamp, data, logconf: Velocity_callback(scf.cf.link_uri, timestamp, data, logconf))
    log_conf4.data_received_cb.add_callback( lambda timestamp, data, logconf: VelTarget_callback(scf.cf.link_uri, timestamp, data, logconf))

    log_conf1.start()
    log_conf2.start()
    log_conf3.start()
    log_conf4.start()
    
# |Position|-|Position_Target|-|Velocity|-|Velocity_Target|

if __name__ == '__main__':
    cflib.crtp.init_drivers()
    factory = CachedCfFactory(rw_cache='./cache')
    with Swarm(uris, factory=factory) as swarm:
        swarm.reset_estimators()
        swarm.parallel_safe(start_position_printing)
        swarm.parallel_safe(run_shared_sequence)

[knmcguire]

Hi! So assigning the logging variables you have done so far, but I guess you would like the variables to become available to the other drones if I'm correct?

I would advise to do the following:

• to put the functions you made in a class, such that you can assign these variables as self.X_1, self,X_2 etc.
• in the log callbacks, you can make an ifstatement that looks at the cfclient URI and assign the logging variables to the right script variables in the script accordingly to the drones
• Do double check it with printouts in the run_shared_sequences if these variables are being written properly

So these things I proposed are perhaps more python related than cflib related so for the specifics it's probably worth a google. But let me know if you don't manage to get something working and I can see if I can provide a minimal example in our cflib

[Morgens2]

Hello again!
Firstly, thanks for answering my message. My goal is to create a function that can do math operations using each drone's data.
So I tried to follow your advise but I got nowhere. If it's easy for you, I would love to see a minimal example. It would be very helpful for me to understand how to make the variables available for operations.
Thank you in advance.

[knmcguire]

Yeah... I think it should be easy to do (famous last words) but the problem is mostly time and priorities. None the less I've opened up an issue as it would sound like an interesting addition, but we don't know when we will have time for it.

As I said before, these things I've proposed are more python related problems and not cflib specific, so I do advise also doing a bit of own digging on the web, perhaps just taking my tips as guidelines as they were intended.

[Morgens2]

I totally understand. I will be waiting for the addition since it will help me with my project. Meanwhile I will do my own digging as you advised and focus on other tasks. Thanks a lot for your time and answers!

[knmcguire]

no prob! I'll update you here if we managed to get an example running, but also update us if you have done it yourself already