Fig. 11 · Nano swarm · crazyflie-firmware 2026.08 · cflib 0.1.34

Crazyflie swarm drone

Fly it

Parts: …
Battery: unplugged
Fault: none

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Pick the battery, motors and props. Every number below is recalculated from this craft's own model.

Battery

Motors

Props

Calculated for this build

All-up weight: 28 g
Thrust : weight: 1.9 : 1
Hover throttle: 73%
Max current: 5 A
Hover time: 6.9 min
Hard-flying time: 6.3 min

Checks

Parts match: 1.9:1, enough margin to hold a tight formation indoors. The calculator keeps the original's part masses; the real drone with both decks weighs about 34 g, so its margin is a little smaller.

WarningIt hovers at 73% throttle: too little headroom to climb out or correct a gust.

Cost

Category	Parts	Cost
Electrical	6	$379
Mechanical	3	$9
Total (approx.)	9	$388

A working emulation of the Crazyflie command line for this craft: real setting names, real limits and real error messages.

cf = scf.cf # connected over Crazyradio

Up and down recall earlier commands.

Configuration snippets

Estimator, controller, Lighthouse and limits after the build

A Crazyflie's parameters are set from Python over the radio: cflib's cf.param.set_value('group.name', value), or the Parameters tab in cfclient. Either deck forces the Kalman filter and PID is the default controller; the base stations here are Lighthouse V2. The posCtlPid limits cap what the position controller may ask for, 20° of lean and 1 m/s, and those are the numbers the range flies.

# cflib 0.1.34 in Python, connected with SyncCrazyflie: cf = scf.cf
cf.param.set_value('stabilizer.estimator', 2)     # extended Kalman: either deck forces it anyway
cf.param.set_value('stabilizer.controller', 1)    # PID (0, auto select, picks PID too)
cf.param.set_value('lighthouse.systemType', 2)    # Lighthouse V2 base stations
cf.param.set_value('lighthouse.method', 1)        # sweep angles straight into the Kalman filter (default)
cf.param.set_value('posCtlPid.rLimit', 20)        # most roll the position controller asks for, degrees
cf.param.set_value('posCtlPid.pLimit', 20)        # and pitch
cf.param.set_value('posCtlPid.xVelMax', 1)        # m/s it may ask for along x
cf.param.set_value('posCtlPid.yVelMax', 1)        # along y
cf.param.set_value('posCtlPid.zVelMax', 1)        # up and down
cf.param.set_value('supervisor.tmblChckEn', 1)    # motors off if it tumbles
cf.param.set_value('pm.lowVoltage', 3.2)          # V: LED1 goes solid red
cf.param.set_value('pm.criticalLowVoltage', 3.0)  # V

Are the decks there? after the build

Each deck announces itself at power-up through its 1-wire ID chip, and the firmware sets a read-only parameter for every deck it finds. get_value returns the value as text, so a script compares it with '1'.

# Read-only: 1 means the deck was found at power-on. get_value returns a string
print(cf.param.get_value('deck.bcFlow2'))
print(cf.param.get_value('deck.bcLighthouse4'))
print(cf.param.get_value('stabilizer.estimator'))

Motor check, one at a time after the build

With the props off, motorPowerSet hands a value from 0 to 65535 straight to each motor's PWM. Run them one at a time and look at the spin from above. The override only acts while the supervisor lets the motors run, and a 2.1+ arms itself; set enable back to 0 when you're done.

# PROPS OFF. The override reaches the motors only while the supervisor lets them run (upright and armed)
cf.param.set_value('motorPowerSet.enable', 1)
cf.param.set_value('motorPowerSet.m1', 10000)     # M1, front right: CCW seen from above
cf.param.set_value('motorPowerSet.m1', 0)
cf.param.set_value('motorPowerSet.m2', 10000)     # M2, rear right: CW
cf.param.set_value('motorPowerSet.m2', 0)
cf.param.set_value('motorPowerSet.m3', 10000)     # M3, rear left: CCW
cf.param.set_value('motorPowerSet.m3', 0)
cf.param.set_value('motorPowerSet.m4', 10000)     # M4, front left: CW
cf.param.set_value('motorPowerSet.m4', 0)
cf.param.set_value('motorPowerSet.enable', 0)     # back to the stabilizer

Propeller test after the build

health.startPropTest spins each motor in turn while the accelerometer measures the shaking. A chipped prop or a tired motor shakes more than the other three. Run it with the props on, on a flat floor.

# Spins each motor in turn and measures the vibration: a chipped prop or a worn motor stands out
cf.param.set_value('health.startPropTest', 1)

The LEDs for the show after the build

Bit 7 of led.bitmask takes the four LEDs away from the firmware's status blinks, and the other bits pick which ones light: 138 is both greens, 148 both reds, 129 the left blue. In the show each drone sets its own value at each point of the star. 0 hands the LEDs back. While the bitmask is on, LED1 can't warn you of a low battery.

# led.bitmask: bit 7 takes the LEDs over from the status blinks, bits 0-5 choose which are lit
cf.param.set_value('led.bitmask', 138)    # 128 + 8 + 2: both green
cf.param.set_value('led.bitmask', 148)    # 128 + 16 + 4: both red
cf.param.set_value('led.bitmask', 129)    # 128 + 1: the left blue
cf.param.set_value('led.bitmask', 0)      # bit 7 clear: the status blinks are back

Hover: MotionCommander for Hover

MotionCommander turns distances into velocity setpoints and streams them every 0.2 s: forward(0.6, velocity=0.4) flies 0.6 m at 0.4 m/s, measured by the Flow deck. Entering the with block takes off to default_height and leaving it lands. The script checks for the Flow deck first, because without it nothing would hold the position.

import time
import cflib.crtp
from cflib.crazyflie import Crazyflie
from cflib.crazyflie.syncCrazyflie import SyncCrazyflie
from cflib.positioning.motion_commander import MotionCommander

URI = 'radio://0/80/2M/E7E7E7E701'

cflib.crtp.init_drivers()
with SyncCrazyflie(URI, cf=Crazyflie(rw_cache='./cache')) as scf:
    if scf.cf.param.get_value('deck.bcFlow2') != '1':
        raise SystemExit('no Flow deck: nothing would hold the position')
    scf.cf.supervisor.send_arming_request(True)
    time.sleep(1.0)
    with MotionCommander(scf, default_height=1.0) as mc:   # takes off to 1 m here
        mc.forward(0.6, velocity=0.4)                     # metres and m/s, measured by the Flow deck
        mc.turn_left(90)                                  # degrees, 72 deg/s
        mc.forward(0.6, velocity=0.4)
        mc.back(0.6)                                      # 0.2 m/s when none is given
    # leaving the with block lands it

Height hold: zdistance setpoints for Height hold

send_zdistance_setpoint takes roll and pitch in degrees, a yaw rate and a height in metres: the Flow deck's range sensor holds the height while you set the lean. Keep sending at 10 Hz or faster, and end with send_notify_setpoint_stop so the high-level commander can take over.

# Inside the same with SyncCrazyflie(...) as scf: block, armed. Setpoints at 10 Hz: miss them for
# 0.5 s and it levels, for 2 s and the motors stop
cf = scf.cf
for _ in range(30):                                   # 3 s: up to 0.8 m, level
    cf.commander.send_zdistance_setpoint(0, 0, 0, 0.8)  # roll, pitch (deg), yaw rate (deg/s), height (m)
    time.sleep(0.1)
for _ in range(20):                                   # 2 s leaning 5 degrees: it drifts, the height holds
    cf.commander.send_zdistance_setpoint(0, 5, 0, 0.8)
    time.sleep(0.1)
for i in range(30):                                   # 3 s back down
    cf.commander.send_zdistance_setpoint(0, 0, 0, 0.8 - i * 0.025)
    time.sleep(0.1)
cf.commander.send_stop_setpoint()
cf.commander.send_notify_setpoint_stop()

Angles and raw thrust for Angle

send_setpoint is roll, pitch, yaw rate and raw thrust, 60000 at most. The firmware ignores the thrust until it has seen a setpoint with thrust 0, so a script starts with one. Nothing holds the height: the thrust you send is all it gets.

# Angles and raw thrust: nothing holds the height or the position. Low, over a net
cf = scf.cf
cf.commander.send_setpoint(0, 0, 0, 0)          # thrust 0 first: until then the firmware locks the thrust
for i in range(20):                             # 2 s: thrust up from 20000 towards hover (60000 is full)
    cf.commander.send_setpoint(0, 0, 0, 20000 + i * 800)
    time.sleep(0.1)
cf.commander.send_setpoint(0, 0, 0, 0)
cf.commander.send_stop_setpoint()

The light show for four for Show

Swarm opens a link to each drone, reset_estimators() waits until every Kalman filter has settled, and parallel_safe runs show() on all four at once, each with its own slot offset. The high-level commander plans each go_to on the drone itself, so a drone that loses its link finishes the leg and holds there instead of dropping. Each leg sets led.bitmask: green, red, green, red, green, then blue to close the star.

import time
import cflib.crtp
from cflib.crazyflie.swarm import CachedCfFactory, Swarm

# four drones on one Crazyradio: one channel, one address each
URIS = [
    'radio://0/80/2M/E7E7E7E701',
    'radio://0/80/2M/E7E7E7E702',
    'radio://0/80/2M/E7E7E7E703',
    'radio://0/80/2M/E7E7E7E704',
]
# each flies the same star from its own corner of a 0.6 m square, so none sits in another one's downwash
SLOT = {URIS[0]: [0.0, 0.0], URIS[1]: [0.6, 0.0], URIS[2]: [0.0, -0.6], URIS[3]: [0.6, -0.6]}
# star points in the Lighthouse frame (m) and the LEDs at each: 138 green, 148 red, 129 blue
STAR = [(4.0, 5.1, 1.5, 138), (3.12, 2.39, 1.2, 148), (5.43, 4.06, 1.5, 138),
        (2.57, 4.06, 1.5, 148), (4.88, 2.39, 1.2, 138), (4.0, 5.1, 1.5, 129)]
LEG = 4.0                                         # s per leg: about 0.8 m/s along a 3 m side


def arm(scf):
    scf.cf.supervisor.send_arming_request(True)
    time.sleep(1.0)


def show(scf, dx, dy):
    cf = scf.cf
    hl = cf.high_level_commander
    hl.takeoff(1.0, 2.0)                          # to 1 m in 2 s, from wherever it stands
    time.sleep(2.5)
    for x, y, z, leds in STAR:
        hl.go_to(x + dx, y + dy, z, 0.0, LEG)     # yaw in radians; it flies on even if the link drops
        cf.param.set_value('led.bitmask', leds)
        time.sleep(LEG)
    cf.param.set_value('led.bitmask', 0)
    hl.go_to(2.0 + dx, 1.6 + dy, 1.0, 0.0, 5.0)   # back over its slot on the pad
    time.sleep(5.0)
    hl.land(0.0, 2.0)
    time.sleep(2.5)
    hl.stop()


if __name__ == '__main__':
    cflib.crtp.init_drivers()
    with Swarm(URIS, factory=CachedCfFactory(rw_cache='./cache')) as swarm:
        swarm.reset_estimators()                  # waits until every Kalman filter has settled
        swarm.parallel_safe(arm)
        swarm.parallel_safe(show, args_dict=SLOT)

Meet the Crazyflie

A Crazyflie is a 29 g quadcopter you program rather than fly. Its 92 mm circuit board is the frame and the flight controller in one, with four coreless motors switched straight from the board and two pin headers for expansion decks. A Flow deck underneath watches the floor and measures the height; a Lighthouse deck on top times the laser sweeps of two base stations and knows where the drone is in the room to a few centimetres. A Python script on a laptop talks to it through a Crazyradio with cflib, and the same radio talks to a whole swarm, each drone on its own address. This one leads four drones through a light show: a five-point star at 0.8 m/s, each drone in its own corner of a 0.6 m square, its LEDs changing colour at every point. Pick the parts, build it, check the motors, the radio link, the decks and the link-loss failsafe, then fly the show by hand or let the high-level commander fly it.

Practice task

Fly in Hover first: take off to 1 m over the pad, then fly the star point to point by hand, slowly. The sticks ask for 1 m/s and 20° of lean at most. Watch the other three keep their slots beside and behind you, then land on the pad. Then switch to Show and let the high-level commander fly it. On a real swarm: give each drone its own address, keep them still and level while they power up, check that both decks read 1, run the motor check and the link-loss test with the props off and the propeller test with them on, and fly the first show low, over a net, with a land command ready in your script.

Build a Crazyflie, check its decks and its radio link, then fly a four-drone light show

Category

Parts

Cost

Electrical

$379

Mechanical

Total (approx.)

$388

# cflib 0.1.34 in Python, connected with SyncCrazyflie: cf = scf.cf cf.param.set_value('stabilizer.estimator', 2) # extended Kalman: either deck forces it anyway cf.param.set_value('stabilizer.controller', 1) # PID (0, auto select, picks PID too) cf.param.set_value('lighthouse.systemType', 2) # Lighthouse V2 base stations cf.param.set_value('lighthouse.method', 1) # sweep angles straight into the Kalman filter (default) cf.param.set_value('posCtlPid.rLimit', 20) # most roll the position controller asks for, degrees cf.param.set_value('posCtlPid.pLimit', 20) # and pitch cf.param.set_value('posCtlPid.xVelMax', 1) # m/s it may ask for along x cf.param.set_value('posCtlPid.yVelMax', 1) # along y cf.param.set_value('posCtlPid.zVelMax', 1) # up and down cf.param.set_value('supervisor.tmblChckEn', 1) # motors off if it tumbles cf.param.set_value('pm.lowVoltage', 3.2) # V: LED1 goes solid red cf.param.set_value('pm.criticalLowVoltage', 3.0) # V

# Read-only: 1 means the deck was found at power-on. get_value returns a string print(cf.param.get_value('deck.bcFlow2')) print(cf.param.get_value('deck.bcLighthouse4')) print(cf.param.get_value('stabilizer.estimator'))

# PROPS OFF. The override reaches the motors only while the supervisor lets them run (upright and armed) cf.param.set_value('motorPowerSet.enable', 1) cf.param.set_value('motorPowerSet.m1', 10000) # M1, front right: CCW seen from above cf.param.set_value('motorPowerSet.m1', 0) cf.param.set_value('motorPowerSet.m2', 10000) # M2, rear right: CW cf.param.set_value('motorPowerSet.m2', 0) cf.param.set_value('motorPowerSet.m3', 10000) # M3, rear left: CCW cf.param.set_value('motorPowerSet.m3', 0) cf.param.set_value('motorPowerSet.m4', 10000) # M4, front left: CW cf.param.set_value('motorPowerSet.m4', 0) cf.param.set_value('motorPowerSet.enable', 0) # back to the stabilizer

# led.bitmask: bit 7 takes the LEDs over from the status blinks, bits 0-5 choose which are lit cf.param.set_value('led.bitmask', 138) # 128 + 8 + 2: both green cf.param.set_value('led.bitmask', 148) # 128 + 16 + 4: both red cf.param.set_value('led.bitmask', 129) # 128 + 1: the left blue cf.param.set_value('led.bitmask', 0) # bit 7 clear: the status blinks are back

import time import cflib.crtp from cflib.crazyflie import Crazyflie from cflib.crazyflie.syncCrazyflie import SyncCrazyflie from cflib.positioning.motion_commander import MotionCommander URI = 'radio://0/80/2M/E7E7E7E701' cflib.crtp.init_drivers() with SyncCrazyflie(URI, cf=Crazyflie(rw_cache='./cache')) as scf: if scf.cf.param.get_value('deck.bcFlow2') != '1': raise SystemExit('no Flow deck: nothing would hold the position') scf.cf.supervisor.send_arming_request(True) time.sleep(1.0) with MotionCommander(scf, default_height=1.0) as mc: # takes off to 1 m here mc.forward(0.6, velocity=0.4) # metres and m/s, measured by the Flow deck mc.turn_left(90) # degrees, 72 deg/s mc.forward(0.6, velocity=0.4) mc.back(0.6) # 0.2 m/s when none is given # leaving the with block lands it

# Inside the same with SyncCrazyflie(...) as scf: block, armed. Setpoints at 10 Hz: miss them for # 0.5 s and it levels, for 2 s and the motors stop cf = scf.cf for _ in range(30): # 3 s: up to 0.8 m, level cf.commander.send_zdistance_setpoint(0, 0, 0, 0.8) # roll, pitch (deg), yaw rate (deg/s), height (m) time.sleep(0.1) for _ in range(20): # 2 s leaning 5 degrees: it drifts, the height holds cf.commander.send_zdistance_setpoint(0, 5, 0, 0.8) time.sleep(0.1) for i in range(30): # 3 s back down cf.commander.send_zdistance_setpoint(0, 0, 0, 0.8 - i * 0.025) time.sleep(0.1) cf.commander.send_stop_setpoint() cf.commander.send_notify_setpoint_stop()

# Angles and raw thrust: nothing holds the height or the position. Low, over a net cf = scf.cf cf.commander.send_setpoint(0, 0, 0, 0) # thrust 0 first: until then the firmware locks the thrust for i in range(20): # 2 s: thrust up from 20000 towards hover (60000 is full) cf.commander.send_setpoint(0, 0, 0, 20000 + i * 800) time.sleep(0.1) cf.commander.send_setpoint(0, 0, 0, 0) cf.commander.send_stop_setpoint()

import time import cflib.crtp from cflib.crazyflie.swarm import CachedCfFactory, Swarm # four drones on one Crazyradio: one channel, one address each URIS = [ 'radio://0/80/2M/E7E7E7E701', 'radio://0/80/2M/E7E7E7E702', 'radio://0/80/2M/E7E7E7E703', 'radio://0/80/2M/E7E7E7E704', ] # each flies the same star from its own corner of a 0.6 m square, so none sits in another one's downwash SLOT = {URIS[0]: [0.0, 0.0], URIS[1]: [0.6, 0.0], URIS[2]: [0.0, -0.6], URIS[3]: [0.6, -0.6]} # star points in the Lighthouse frame (m) and the LEDs at each: 138 green, 148 red, 129 blue STAR = [(4.0, 5.1, 1.5, 138), (3.12, 2.39, 1.2, 148), (5.43, 4.06, 1.5, 138), (2.57, 4.06, 1.5, 148), (4.88, 2.39, 1.2, 138), (4.0, 5.1, 1.5, 129)] LEG = 4.0 # s per leg: about 0.8 m/s along a 3 m side def arm(scf): scf.cf.supervisor.send_arming_request(True) time.sleep(1.0) def show(scf, dx, dy): cf = scf.cf hl = cf.high_level_commander hl.takeoff(1.0, 2.0) # to 1 m in 2 s, from wherever it stands time.sleep(2.5) for x, y, z, leds in STAR: hl.go_to(x + dx, y + dy, z, 0.0, LEG) # yaw in radians; it flies on even if the link drops cf.param.set_value('led.bitmask', leds) time.sleep(LEG) cf.param.set_value('led.bitmask', 0) hl.go_to(2.0 + dx, 1.6 + dy, 1.0, 0.0, 5.0) # back over its slot on the pad time.sleep(5.0) hl.land(0.0, 2.0) time.sleep(2.5) hl.stop() if __name__ == '__main__': cflib.crtp.init_drivers() with Swarm(URIS, factory=CachedCfFactory(rw_cache='./cache')) as swarm: swarm.reset_estimators() # waits until every Kalman filter has settled swarm.parallel_safe(arm) swarm.parallel_safe(show, args_dict=SLOT)

Meet the Crazyflie

Practice task

Build a Crazyflie, check its decks and its radio link, then fly a four-drone light show

Crazyflie swarm drone

Design it

Calculated for this build

Checks

Cost

Build it

Try a real mistake

Selected part

Parts in the box

Wiring

Safety tests

Motor check (props off)

Sensor calibration (keep it still)

Crazyradio link

Decks and positioning

Link-loss test (props off)

cflib console

Configuration snippets

Estimator, controller, Lighthouse and limits after the build

Are the decks there? after the build

Motor check, one at a time after the build

Propeller test after the build

The LEDs for the show after the build

Hover: MotionCommander for Hover

Height hold: zdistance setpoints for Height hold

Angles and raw thrust for Angle

The light show for four for Show

Check yourself · Plug in the motors

Check yourself · Fit the Lighthouse deck on top

Check yourself

Meet the Crazyflie

Practice task

Crazyflie swarm drone

Design it

Calculated for this build

Checks

Cost

Build it

Try a real mistake

Selected part

Parts in the box

Wiring

Safety tests

Motor check (props off)

Sensor calibration (keep it still)

Crazyradio link

Decks and positioning

Link-loss test (props off)

cflib console

Configuration snippets

Estimator, controller, Lighthouse and limits after the build

Are the decks there? after the build

Motor check, one at a time after the build

Propeller test after the build

The LEDs for the show after the build

Hover: MotionCommander for Hover

Height hold: zdistance setpoints for Height hold

Angles and raw thrust for Angle

The light show for four for Show

Check yourself · Plug in the motors

Check yourself · Fit the Lighthouse deck on top

Check yourself

Meet the Crazyflie

Practice task