[![I uploaded piscope image and same time output image also for better understanding of issues][1]][1]I am using sample code of Pypi from "http://abyz.co.uk/rpi/pigpio/python.html" to detect frequency from function generator but frequency not coming constant .For verifying my input frequency i checked it on CRO where i got frequency is constant i.e 4.985khz but on raspberry its showing 4.805khz and 5.000khz.
here is my code
import time
import pigpio # http://abyz.co.uk/rpi/pigpio/python.html
class reader:
def __init__(self, pi, gpio, weighting=0.0):
self.pi = pi
self.gpio = gpio
if weighting < 0.0:
weighting = 0.0
elif weighting > 0.99:
weighting = 0.99
self._new = 1.0 - weighting # Weighting for new reading.
self._old = weighting # Weighting for old reading.
self._high_tick = None
self._period = None
self._high = None
pi.set_mode(gpio, pigpio.INPUT)
self._cb = pi.callback(gpio, pigpio.EITHER_EDGE, self._cbf)
def _cbf(self, gpio, level, tick):
if level == 1:
if self._high_tick is not None:
t = pigpio.tickDiff(self._high_tick, tick)
if self._period is not None:
self._period = (self._old * self._period) + (self._new * t)
else:
self._period = t
self._high_tick = tick
elif level == 0:
if self._high_tick is not None:
t = pigpio.tickDiff(self._high_tick, tick)
if self._high is not None:
self._high = (self._old * self._high) + (self._new * t)
else:
self._high = t
def frequency(self):
"""
Returns the PWM frequency.
"""
if self._period is not None:
return 1000000.0 / self._period
else:
return 0.0
def cancel(self):
self._cb.cancel()
if __name__ == "__main__":
import time
import pigpio
import read_PWM
PWM_GPIO = 4
RUN_TIME = 60.0
SAMPLE_TIME = 2.0
pi = pigpio.pi()
p = read_PWM.reader(pi, PWM_GPIO)
start = time.time()
while (time.time() - start) < RUN_TIME:
time.sleep(SAMPLE_TIME)
f = p.frequency()
print("f={:.1f}".format(f)
p.cancel()
[1]: https://i.stack.imgur.com/2a1UP.jpg
