Helicopter animation using a Raspberry Pi

What I think you need for flashing led2 is a timer routine.  In theory, when you wanted the LED2 to start flashing, you would clear a counter(if needed), and start the timer.  When the time expires (this could be you flashing rate) the timer routine would toggle the LED2 GPIO pin, reset the counter(if using), and exit.  Then when you wanted to stop the LED2 flashing, you would just have to stop the timer.  No threading or multiprocessing needed...

Thank for your input.

I have developed a routine that results in a LED2 flash that simulates a strobe. Varying the on and off times gives me the strobe effect I was looking for. When the routine is called, using my programming skills, the strobes either flash but the other LED's don't change or all the LEDs light up and nothing after that.

House  isolation gives me the time to keep programming. Keep the suggestions coming.

Try looking here for hints on how to use a timer:  https://www.geeksforgeeks.org/timer-objects-python/

Is this what you want to do:

LED1 on

LED2 start flashing

LED3 on, LED2 keep flashing

LED4 on, LED2 keep flashing

<time passess>LED2 keep flashing

LED4 off, LED2 keep flashing

LED3 off, LED2 keep flashing

LED2 off, LED2 stop flashing

LED1 off, LED2 still off

repeat...

Probably, this is the most elegant and efficient solution. The possible alternative I see is managing interrupts chained so every state set to a different state in the others but this is tricky and not interesting in this case. A real alternative, instead, at least in my opinion, is creating a dictionary in Python collecting every change in a different boolean variable. Then a single function will set/reset the LEDs on/off as well as the motor, sound, and any other part that should be included in the animation. This optimizes the code and makes easier to change the pattern of the animation.

In the main infinite cycle while true if using a json file with different animation patterns these can be randomly looped to get a more interesting effect.

Enrico

Sorry M, you're going to have to dummy down your response for me to process. I'm the dummy:) I'm inputting at the rate of a paper tape reader punch and your outputting at the rate of SCSI 2 interface.

I see some benefit to the concept of "Then a single function will set/reset the LEDs on/off as well as the motor, sound, and any other part that should be included in the animation." Understand the goal is to integrate the three components of animation, lights, sound and motions is important.  Unfortunately, I don't have the knowledge level to extrapolate what I need to do to accomplish this.

I'm stuck on the simple concept of concurrency. Two tasks operating independently. On and off LED's and LED strobe on and LED strobe off. How do I do that?

Yes V Squared the additional commentary in the sequence is correct! Your additional commentary enhances to detail of what I am trying to accomplish.

The pilots are in the helicopter running through a startup checklist. More than one thing happen at the same time. Lights will come on solid and some will flash. engines will start later generating sound and motor will engage rotors to turn.. The viewer on the outside just sees lights, hears engines and witnesses motion of the blades.

My goal is to create this sequence using a Pi running python.

Your problem could be handled with concurrent processes and it seems simple enough that you have a few things that might be independently occurring, but when you dive into implementing concurrency in a computer, it rapidly becomes a very complex topic. I doubt it could be distilled down to a paragraph of advice that would avoid a big learning curve.

If you want to describe your problem a bit more theoretically than just the mechanics of loops, you could look into state machines. This problem can be described as a system that has different states at different times and the states follow a sequence. At any given time some, things are on and others are off - that defines the state of the system at that time. The loop counter we mentioned above is a way to implement a state machine. Every quarter second the system enters a new state. You just need to decide what needs to be on and what needs to be off in each quarter second.

So this is what I whipped up quickly.  I have not tested or compiled this, but it works great in my head...

import threading
import RPi.GPIO as GPIO


def LED2_Blinker():
if GPIO.input (LED2_PIN): #read teh led2 pin and if it is high, set it low
GPIO.output (LED2_PIN, GPIO.LOW)
else: #was not high, set it so...
GPIO.output (LED2_PIN,GPIO.HIGH)

LED1_PIN = XX #change XX to be proper pin number on PI
LED2_PIN = XX #change XX to be proper pin number on PI
LED3_PIN = XX #change XX to be proper pin number on PI
LED4_PIN = XX #change XX to be proper pin number on PI


GPIO.setup (LED1_PIN, GPIO.OUT)
GPIO.setup (LED2_PIN, GPIO.OUT)
GPIO.setup (LED3_PIN, GPIO.OUT)
GPIO.setup (LED4_PIN, GPIO.OUT)


#set all pins low to start....
GPIO.output (LED1_PIN,GPIO.LOW)
GPIO.output (LED2_PIN,GPIO.LOW)
GPIO.output (LED3_PIN,GPIO.LOW)
GPIO.output (LED4_PIN,GPIO.LOW)


#setup the timer.  Number is for amount of time between timer activating...
timer = threading.Timer(0.25,LED2_Blinker)


# and now the looping sequence...
while True:
GPIO.output (LED1_PIN,GPIO.HIGH)
time.sleep(3)
timer.start() #starts the timer so that LED 2 will blink automagically
GPIO.output (LED3_PIN,GPIO.HIGH)
time.sleep(3)
GPIO.output (LED4_PIN,GPIO.HIGH)
time.sleep(3)
#done startup sequence...
GPIO.output (LED4_PIN,GPIO.LOW)
time.sleep(3)
GPIO.output (LED3_PIN,GPIO.LOW)
time.sleep(3)
timer.cancel() #stops the tiemr from firing until restarted...
GPIO.output (LED2_PIN,GPIO.LOW) #ensure that LED2 is off (just in case)
GPIO.output (LED1_PIN,GPIO.LOW)
time.sleep(3)

This should repeat forever, until you power it off...

I have just a doubt. The timer should be started inside the loop?

I have just a doubt. The timer should be started inside the loop?

I don't think there is anything wrong with starting a timer in a loop because LED2 can't start blinking until after LED1 is has been on for 3 seconds.  The timer was setup before the while loop started, so when the timer expires/fires, it will run the LED2_Blinker routine and then exit and wait for another timeout.  This way returns the control back to the main while loop so it can run again...