Method to create a daemon on Python

Question

using a raspberry pi and python,we get data from a rotary encoder using the input pins.There will be a second program that will run c# on mono,and will read this data from python code at some intervals.What's the best way to create a daemon that keeps reading the io ports as long as the encoder rotates? The encoder reader uses a while while true loop to read the data such as:

while True:
encoderPinA=GPIO.input(8)
encoderPinB=GPIO.input(9)
if (encoderPinA == True) and (oldPinA == False):    
            if (encoderPinB == False):              
                    Position=Position+inc           
            else:                                  
                    Position=Position-inc          
            print Position ..so on...

Also whats the best way to transfer this data from python to c#? I'm intending to write to a file from python at some intervals and reading the data from c#,but it wouldn't be very responsive.

What does the C# program do, Better to write both in Python? Also, You can write out JSON files and consume them in C# For Daemon - http://stackoverflow.com/questions/1603109/how-to-make-a-python-script-run-like-a-service-or-daemon-in-linux — Hitesh Dharamdasani, May 25 '15 at 06:17
It's a lot simpler (and more responsive) to send data between processes with a `pipe`, Unix socket, or localhost UDP socket than with a regular file. Which of the three is appropriate depends on how they're launched, and what the sender should do if the receiver isn't ready. — abarnert, May 25 '15 at 07:24
Meanwhile, for the implementing a daemon part, see [python-daemon](https://pypi.python.org/pypi/python-daemon/). (This library can also be used to add a service wrapper, or you can just use the system service wrapper or manually launching.) — abarnert, May 25 '15 at 07:25

score 1 · Answer 1 · answered Jul 15 '15 at 14:54

I'm afraid this is probably too late, but I recently ported some rotary encoder code from the PigPio library (http://abyz.co.uk/rpi/pigpio/ex_rotary_encoder.html) to C# using the Raspberry-Sharp-IO library: https://github.com/raspberry-sharp/raspberry-sharp-io . This would eliminate the requirement for Python and keep everything 'under one roof'.

With the rotary encoder pins hooked to connector pin 24 (referenced by the library as Pin08), ground and connector pin 26 (referenced by the library as Pin7):

using System;
using Raspberry.IO.GeneralPurpose;

namespace GPIOTesting
{
    class Program
    {
        //State of Pin08
        private static bool levA = false;
        //State of Pin7
        private static bool levB = false;
        //The name of the last GPIO pin to fire a PinStatusChanged event
        private static string lastGpio = String.Empty;

        static void Main(string[] args)
        {
            //Declare our pins (connector 24 and 26 / processor 08 and 7) as INPUT pins, and apply pull-up resistors
            var pin1 = ConnectorPin.P1Pin24.Input().PullUp();
            var pin2 = ConnectorPin.P1Pin26.Input().PullUp();

            //Create the settings for the connection
            var settings = new GpioConnectionSettings();

            //Interval between pin checks. This is *really* important - higher values lead to missed values/borking. Lower 
            //values are apparently possible, but may have 'severe' performance impact. Further testing needed.
            settings.PollInterval = TimeSpan.FromMilliseconds(1);

            //Create a new GpioConnection with the settings per above, and including pin1 (24) and pin2 (26).
            var connection = new GpioConnection(settings, pin1, pin2);

            //Integer storing the number of detents turned - clockwise turns should increase this and vice versa.
            var encoderPos = 0;

            //Add an event handler to the connection. If either pin1 or pin2's value changes this will fire.
            connection.PinStatusChanged += (sender, eventArgs) =>
                    {
                        //If pin 24 / Pin08 / pin1 has changed value...
                        if (eventArgs.Configuration.Pin == ProcessorPin.Pin08)
                        {
                            //Set levA to this pin's value
                            levA = eventArgs.Enabled;
                        }
                        //If any other pin (i.e. pin 26 / Pin7 / pin2) has changed value...
                        else
                        {
                            //Set levB to this pin's value
                            levB = eventArgs.Enabled;
                        }

                        //If the pin whose value changed is different to the *last* pin whose value changed...
                        if (eventArgs.Configuration.Pin.ToString() != lastGpio)
                        {
                            //Update the last changed pin
                            lastGpio = eventArgs.Configuration.Pin.ToString();

                            //If pin 24 / Pin08 / pin1's value changed and its value is now 0...
                            if ((eventArgs.Configuration.Pin == ProcessorPin.Pin08) && (!eventArgs.Enabled))
                            {
                                //If levB = 0
                                if (!levB)
                                {
                                    //Encoder has turned 1 detent clockwise. Update the counter:
                                    encoderPos++;
                                    Console.WriteLine("UP: " + encoderPos);
                                }
                            }
                            //Else if pin 26 / Pin7 / pin2's value changed and its value is now 1...
                            else if ((eventArgs.Configuration.Pin == ProcessorPin.Pin7) && (eventArgs.Enabled))
                            {
                                //If levA = 1
                                if (levA)
                                {
                                    //Encoder has turned 1 detent anti-clockwise. Update the counter:
                                    encoderPos--;
                                    Console.WriteLine("DOWN: " + encoderPos);
                                }
                            }
                        }
                    };
        }
    }
}

Method to create a daemon on Python

1 Answers1