def modulate(edges, carrier_freq, duty_cycle=0.5, polarity=IRConfig.IdleLow):
'''Modulate an edge stream
This is a generator function.
edges (edge stream)
The edge stream to modulate
carrier_freq (float)
The modulation frequency
duty_cycle (float)
The duty cycle of the modulation
polarity (infrared.IRConfig)
Set the polarity (idle state high or low)
Yields an edge stream.
'''
duty_cycle = max(min(duty_cycle, 1.0), 0.0) # constrain to 0.0 - 1.0
# Invert edge polarity if idle-high
if polarity == IRConfig.IdleHigh:
edges = ((t, 1 - e) for t, e in edges)
mod_period = (1.0 / carrier_freq)
high_time = mod_period * duty_cycle
low_time = mod_period * (1.0 - duty_cycle)
es = EdgeSequence(edges, mod_period)
yield (es.cur_time, es.cur_state()) # initial state
while not es.at_end():
es.advance_to_edge()
while es.cur_state() == 1:
yield (es.cur_time, 1)
es.advance(high_time)
yield (es.cur_time, 0)
es.advance(low_time)
yield (es.cur_time, es.cur_state()) # final state
