class PWM():
# free RMT channel table
RMT_channels = [False, False, False, False, False, False, False, False]
def __init__(self, pwm_pin, freq=5000, duty=512):
for idx in range(len(PWM.RMT_channels)):
if not PWM.RMT_channels[idx]: # find free channel
PWM.RMT_channels[idx] = True
# mark used cnannel
self.RMT_channel = idx # keep the channel number
self.RMT_obj = RMT(idx, pin=pwm_pin, clock_div=80)
self.pwm_duty = 512
self.pwm_freq = 5000
self.init(freq, duty)
break
else:
raise RuntimeError('No RMT channel available.')
def run(self):
period = 1000000 / (self.pwm_freq)
up_time = round(period * (self.pwm_duty / 1023))
down_time = round(period) - up_time
self.RMT_obj.loop(False)
self.RMT_obj.write_pulses((up_time, down_time), start=1)
self.RMT_obj.loop(True)
# MicroPython 1.13 requires loop() running before write_pulses()
# MicroPython 1.12 would report error if loop() runs before any write_pulses()
self.RMT_obj.write_pulses((up_time, down_time), start=1)
def freq(self, new_freq):
self.pwm_freq = new_freq if new_freq > 15 else 16
self.run()
def duty(self, new_duty):
self.pwm_duty = new_duty if new_duty < 1023 else 1023
self.run()
def deinit(self):
self.RMT_obj.deinit()
PWM.RMT_channels[self.RMT_channel] = False
def init(self, freq=5000, duty=512):
self.freq(freq)
self.duty(duty)
# second counter 0-59
second=bytearray(1)
# TX bits for one minute
minute=bytearray(59)
# index for writing to minute[]
index=bytearray(1)
# 1-second timer
timer=Timer(3)
# last day NTP was set
ntpday=0
led=Pin(2,Pin.OUT)
antena=Pin(15,Pin.OUT)
ask=RMT(0,pin=antena,carrier_freq=0,clock_div=1) # 80 MHz
ask.loop(True)
if disp:
import ssd1306
i2c = I2C(scl=Pin(4), sda=Pin(5))
oled = ssd1306.SSD1306_I2C(128, 64, i2c, 0x3c)
oled.fill(0)
oled.text("DCF77", 0, 0)
oled.show()
weekdaystr = ["MO","TU","WE","TH","FR","SA","SU"]
# desired carrier frequency
freq=77500
# tuning paramters - adjust with scope
# coarse tuning, about 75 Hz per step