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Pioreactor / rpi_hardware_pwm

Access the hardware PWM of a Raspberry Pi
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Invalid argument Error on change_frequency #1

Closed tobiaszehntner closed 3 years ago

tobiaszehntner commented 3 years ago

Hi there,

When trying to change frequency I get an Invalid Argument error:

p = HardwarePWM(1, hz=200)
p.start(0)
p.change_duty_cycle(80)
p.change_frequency(50)
Traceback (most recent call last):
  File "/home/pi/.pycharm_helpers/pydev/_pydevd_bundle/pydevd_exec2.py", line 3, in Exec
    exec(exp, global_vars, local_vars)
  File "<input>", line 1, in <module>
  File "/usr/local/lib/python3.7/dist-packages/rpi_hardware_pwm/__init__.py", line 98, in change_frequency
    self.change_duty_cycle(self._duty_cycle)
  File "/usr/local/lib/python3.7/dist-packages/rpi_hardware_pwm/__init__.py", line 91, in change_duty_cycle
    self.echo(dc, os.path.join(self.pwm_dir, "duty_cycle"))
  File "/usr/local/lib/python3.7/dist-packages/rpi_hardware_pwm/__init__.py", line 66, in echo
    f.write(f"{m}\n")
OSError: [Errno 22] Invalid argument
CamDavidsonPilon commented 3 years ago

Hi wow sorry I missed this!

Yes, what happened was this error: https://stackoverflow.com/questions/23050738/beaglebone-pwm-limited-to-100-hz/23050835#23050835

Always set duty_cycle to zero BEFORE you set the frequency if the previous value will not fit into the new period, this avoids frustration.

However, this library should figure this out for you! (Or aleast provide a better error message).

CamDavidsonPilon commented 3 years ago

👋 should error be fixed (i.e avoidable) in the latest version 0.1.1