Hi Peter,
> This quite long because the guy that wrote it documented every step.
And because this chunk in the middle is repeated. :-)
> frequency_hertz = 50
> pwm = GPIO.PWM(pin_number, frequency_hertz)
>
>
> # How to position a servo? All servos are pretty much the same.
> # Send repeated purses of an absolute duration (not a relative duty cycle)
> # between 0.40 ms and 2.5 ms in duration. A single pulse will only move it
> # a short distance in the desired direction. Repeated pulses will continue
> # its movement and then once it arrives at the specified position it will
> # insruct the motor to forcefully hold its position.
> left_position = 0.40
> right_position = 2.5
> middle_position = (right_position - left_position) / 2 + left_position
>
> # I'll store a sequence of positions for use in a loop later on.
> positionList = [left_position, middle_position, right_position,
> middle_position]
>
> # total number of milliseconds in a a cycle. Given this, we will then
> # know both how long we want to pulse in this cycle and how long tghe
> # cycle itself is. That is all we need to calculate a duty cycle as
> # a percentage.
> ms_per_cycle = 1000 / frequency_hertz
>
Note his ordering of using `pwm' in the loop, stopping afterwards, and
then `cleaning up' GPIO.
> for i in range(3):
> for position in positionList:
> duty_cycle_percentage = position * 100 / ms_per_cycle
> pwm.start(duty_cycle_percentage)
> time.sleep(.5)
>
> pwm.stop()
> GPIO.cleanup()
And compare it with yours where the `pwm' is in a callback function to
handle the URL,
> @app.route('/motor-forwards/')
> def motorforwards():
> duty_cycle_percentage = left_position * 100 / ms_per_cycle
> pwm.start(duty_cycle_percentage)
> time.sleep(.5)
> pwm.stop()
> return render_template('index.html')
And the GPIO clean-up is after that definition, just before you decide
to hand control over to Flask by calling app.run().
> GPIO.cleanup()
>
> if __name__ == '__main__':
> app.run(debug=True, host='0.0.0.0')
You're cleaning up the GPIO before Flask gets to run and that probably
undoes all your GPIO and PWM configuration. Assuming run() can return,
I forget, move the clean up:
if __name__ == '__main__':
app.run(debug=True, host='0.0.0.0')
GPIO.cleanup()
--
Cheers, Ralph.
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