def main():
'''
Makes a LED to blink according to the distance meassured
by an ultrasonic sensor.
Finish when user press a toggle key.
'''
blinker = Blinker(27, MAX_DELAY) #P8.17
ultrasonic = Ultrasonic(66, 69) #P8.7, P8.9
key = Gpio(65, Gpio.IN) #P8.18
try:
print("Ready. Press toggle key to start.")
#Wait for key down event
while key.getValue() == Gpio.LOW:
sleep(0.2)
#Wait for key up event
while key.getValue() == Gpio.HIGH:
sleep(0.2)
print("Started. Press toggle key again to finish.")
blinker.start()
while key.getValue() == Gpio.LOW:
dist = ultrasonic.read()
delay = calculateDelay(dist)
blinker.setDelay(delay)
sleep(0.2)
print("Bye!")
finally:
key.cleanup()
blinker.stop()
blinker.cleanup()
ultrasonic.cleanup()
from time import sleep
led = Gpio(27, Gpio.OUT) #P8.17
key = Gpio(65, Gpio.IN) #P8.18
try:
light = Gpio.LOW
led.setValue(light)
lastKeyState = Gpio.LOW
print("Ready.\nPress toggle key to change led state or Ctrl+C to exit.")
while True:
keyState = key.getValue()
if lastKeyState != keyState and keyState == Gpio.HIGH:
light = not light
led.setValue(light)
print("Led state changed to {0}.".format("ON" if light else "OFF"))
lastKeyState = keyState
sleep(0.2)
except KeyboardInterrupt:
print("\nBye!")
finally:
led.setValue(Gpio.LOW)
class Ultrasonic(object):
PULSE2CM = 17241.3793 # cm/s
MAX_RANGE = 3500 # cm
OUT_OF_RANGE = 0xffffffff
def __init__(self, triggerPort, echoPort, nSamples=5):
'''
Constructor
@param triggerPort: Port number of the trigger signal
@param echoPort: Port number of the echo port
@param nSamples: Number of samples to measure the distance
'''
self._nSamples = nSamples
#Configure ports
self._trigger = Gpio(triggerPort, Gpio.OUT)
self._trigger.setValue(Gpio.LOW)
self._echo = Gpio(echoPort, Gpio.IN)
time.sleep(2)
def read(self):
'''
Measures distance
@return: Distance as centimeters
'''
MAX_POLL = 1000
i = 0
dist = 0
while i < self._nSamples and dist != Ultrasonic.OUT_OF_RANGE:
self._trigger.setValue(Gpio.HIGH)
time.sleep(0.001)
self._trigger.setValue(Gpio.LOW)
#TODO: use system's poll mechanism or event to wait for GPIO-level change
nPoll = 0
while nPoll < MAX_POLL and self._echo.getValue() == Gpio.LOW:
nPoll += 1
if nPoll == MAX_POLL:
raise ReadGpioException(
"Max poll reached: waiting for echo HIGH")
pulseStart = time.time()
nPoll = 0
while nPoll < MAX_POLL and self._echo.getValue() == Gpio.HIGH:
nPoll += 1
if nPoll == MAX_POLL:
raise ReadGpioException(
"Max poll reached: waiting for echo LOW")
pulseEnd = time.time()
pulseDuration = pulseEnd - pulseStart
distSample = round(pulseDuration * Ultrasonic.PULSE2CM, 0) #cm
if distSample < Ultrasonic.MAX_RANGE:
dist = (dist + distSample) / 2.0 if i != 0 else distSample
else:
dist = Ultrasonic.OUT_OF_RANGE
i += 1
return dist
def cleanup(self):
'''
Frees ressources
'''
self._trigger.cleanup()
self._echo.cleanup()
