python code to control GPIO at specific times

Question

I want to build an irrigation automation system based on a Raspberry Pi. I have a script that generates a .CSV file based on the input parameters of the sprinkeling schedule (station no, time/station, use/not use rain sensor, etc.).

The .CSV file looks like this:

1 00:00:00 00:29:59 110000
2 00:30:00 00:44:59 101000
3 00:45:00 01:14:59 100100
.
.
.
.

, where each line represent a time interval and the six digits binary number represent the GPIO pins state (1=valve on, 0=valve off).

What is the best way to scan this .CSV file and trigger the valves based on the binary code?

For now I have two options, but I'm sure there must be a better one:

Continuously loop a code at 1 second interval, read each line of the .CSV file until the interval mathes the current time and then trigger the correspondent ports
Read a .CSV file and generate a cron job for each line

Either way, the solution has to be very simple and very reliable, the program is supposed to run during the entire summer season without mistake or error.

Thanks!

It might be worth posting this in the python forum on the raspberry pi website too, or the raspberry pi stackexchage site. StackOverflow is more helping you fix errors in your code. — elParaguayo, Jul 30 '15 at 19:15

score 2 · Answer 1 · answered Jul 30 '15 at 19:38

This program should do what you want it to. When it starts, your file is read into a schedule. The schedule is sorted, and the for loop runs through your schedule as needed. Once the schedule has been completed, your program will need to be run again.

import operator
import time


def main():
    schedule = []
    with open('example.csv') as file:
        for line in file:
            _, start, _, state = line.split()
            data = time.strptime(start, '%H:%M:%S')
            schedule.append((time_to_seconds(data), int(state, 2)))
    schedule.sort(key=operator.itemgetter(0))
    for start, state in schedule:
        current_time = time_to_seconds(time.localtime())
        difference = start - current_time
        if difference >= 0:
            time.sleep(difference)
            set_gpio_pins(state)


def time_to_seconds(data):
    return (data.tm_hour * 60 + data.tm_min) * 60 + data.tm_sec


def set_gpio_pins(state):
    raise NotImplementedError()

if __name__ == '__main__':
    main()

@user3254924, https://stackoverflow.com/questions/419163/what-does-if-name-main-do — Alyssa Haroldsen, Jul 31 '15 at 22:02
The standard library already contains the `sched` module, so maybe you are reinventing the wheel here. :-) — BlackJack, Aug 05 '15 at 09:22

score 0 · Answer 2 · answered Jul 31 '15 at 21:36

0

A possible idea could be to use crontab to run a program that scans the .CSV file and also triggers the valves, so that you can do this only when you really need it.

answered Jul 31 '15 at 21:36

I have a very bad experience with the Task Scheduler in Windows, it is very unreliable. Is the crontab 100% reliable? – user3254924 Aug 05 '15 at 04:58
@user3254924 So far, I've never experienced any issue with crontab, and I use it every day on my Raspberry Pi. – Aug 05 '15 at 06:39

score -1 · Answer 3 · answered May 12 '17 at 16:27

-1

You might want to look into trying the linux clock commands to help set when your sprinklers will go off:

#this is pseudocode
While True :

    If *clocktime* == *target activation time*
         *these sprinklers activate*

answered May 12 '17 at 16:27

Ryan Louis

11
7

python code to control GPIO at specific times

3 Answers3