self-organizing systems with many picAXEs

[AlC]

Hi all,

I've been reading something over at instructables that triggered my interest: an array of LEDs simulating the self-organizing behaviour of a swarm of blinking fireflies. The LEDs start out by emitting random flashes of light, but with time they synchronize to each other and finally they all blink synchronized (each of the LEDs has a small Atiny12 and a light-dependent resistor) Since I like the idea I want to copy this with several picAXE08 (I don't like atmel chips since I can't write code for them).

But before going out and buying a whole bunch of picaxe08, I thought I'd like to have some opinions on the software I wrote for it - specifically my fears are that the individual "fireflies"/circuits will not differ enough in their initial delay before they start their blink'n sync adventures..

I've tried to fill a word variable with "random" value and then use only 1 byte of that, can anyone have a look at the code please and tell me what they think - will this cause the fireflies initial (still unsynchronized) behaviour to be "individual" enough, or will the more or less all start at the same time?

Will the program work at all?

thanks

heres my code

; *** FIREFLY.BAS  ************ Version 1.0 beta *******  SELF-SYNCHRONIZING NETWORK OF LED FIREFLIES  ***
; this program is intended for simulation of a swarm of fireflies by many individually controlled LEDs, designed
; to run on a PICaxe08 with a LDR connected to pin 1  and one LED wired to pin 2 (each firefly needs one PICaxe)
; Since they are totally independent besides of sharing the same reset switch, one can easily combine any number of 
; fireflies to form a large array of blinking, self-organizing LEDs...  pressing the "reset" switch will of course disturb 
; the fireflies and their uniform blinking pattern, like walking right into a swarm would disturb real blinking fireflies too, 
; probably, and it takes awhile before they start blinking and syncing again...
; --------------------------------------------------------------------------------------------------------------------------------------------------
; Copyright (c) 15/05/2009 
; Dennis Schulze

; variables
symbol Power = w4               ;determines how urgently the firefly wants to pulse or how hard it "desires" to do so 
symbol Brightness=b2          ;this later contains the reading of the LDR value
symbol Ambient =b3             ;initial ambient light intensity value is stored here for comparison reasons
symbol BlinkCounter =  b4    ;Counter needed for initialisation blinking loop
symbol RndDelay = b1          ;this will be seeded with a random number for individual delay time

; constants
symbol Daylight=195              ; above this light intensity threshold the firefly does not glow at all (i.e. if its not "night")
symbol MaxPower = 80        ; Urgency threshold that triggers an immediate pulse

;counters
let BlinkCounter = 1                ;reset all counters
let Power = 1			;


;randomize a bit to give individuality
random w0                          ;generate "random" 16bit number (hopefully differing enough between individual PICaxe ICs)..
let RndDelay = b1 * 24        ;take the last 8bit of it and multiply by 24 to give several seconds delay at most


; initialisation blinking loop
for BlinkCounter = 1 to 5    ; blink five times
	gosub pulse
	pause 700
	BlinkCounter = BlinkCounter + 1
next BlinkCounter	




 pause 1500                            ; wait long enough to make sure that absolutely NO firefly is blinking at the moment
readadc 1, Ambient             ; then read out ambient light intensity and store value in "Ambient"
pause RndDelay                     ; pause for an "individual" (hopefully) amount of time before doing anything else



main: do        ; main loop


	
	let Power = Power + 1     ; slowly start incrementing the fireflie's desire to blink..

	
	readadc 1, Brightness     ;...while watching the surrounding fireflies too!

	
	if Brightness >= Daylight then      ; unless its daytime (fireflies are sleeping during daytime!)...

		sleep 3

	endif

	
	if Brightness > Ambient then       ;......perceiving pulses from other fireflies will

		Power = Power + 50             ;..strongly increase our fireflys desire to pulse with them!

	endif

	
	if Power > MaxPower then          ; if the desire is strong enough... 

		gosub pulse		; ...the firefly bursts out a light pulse
			
	        let Power = 1         ; what a relief for the firefly! "desire" is reset to initial value 
	        				; (equals satisfaction about just having pulsed) 
	  
	 endif

				
loop       ;  starts building desire for another pulse again (while slowly approximating the other's frequencies)





;subroutine
pulse:

    high 2             ; give a short flash of light
    pause 300
    low 2

return

[eclectic]

@Dennis

"Will the program work at all?"

Have you tried it?
If only in Simulation.



e

[AlC]

Not in hardware since I don't have many spare picaxe08 lying around, which is prerequisite for this project.

The program does simulate well though, the "LED" flashes from time to time while slowly incrementing the "desire" by 1 at a time, when I raise the adc value manually this triggers the LED to flash almost immediately which is what it should do.

I'm only concerned about diversity between single chips: will a number generated individually on each chip with "random" differ enough between single picaxe08 to make it possible that they all start at different times when all are switched on at once? They should not be synchronized at the beginning already thats why I ask. The effect is that they need some time to get into sync with each other.. ..looks very interesting when you watch it.

But for this to happen, they need to be off-sync to begin with. This is achieved by having each "firefly" wait an individual amnt of time before it starts blinking and syncing. So a good random value is needed for calculating this individual delay. the Picaxe08 doesn't have any internal clock the random number could be seeded with (like with the picaxe X chips), but I hope their internal oscillators are all slightly different enough. (?)

anyone know code for generating good (diverse between single chips!!) random numbers?

[eclectic]

Here's a starter thread.

http://www.picaxeforum.co.uk/showthread.php?t=7799

Afterwards, perhaps consider randomised "Start" timings
for the 08(M) chips?

e

[Jeremy Leach]

Interesting !

I've not studied it in detail but - If you're powering up all picaxes at the same time then I think you'll need to have a different 'seed' for the random part, becuase it's only pseudo random on a picaxe. However I'd personally not get hung up on the random aspect and just have different preset constants for each picaxe.

Also, you might find the LDRs have trouble detecting the light pulses from the LEDs??

So, what stops real fireflies all speeding up I wonder?! Do they have an inbuilt frequency?

[Andrew Cowan]

To get truly different delays, put pause 3 at the top of one 08Ms code, pause 7 at the top of the next's, pause 11 at the top of the next...

A

[boriz]

Use the LDR to get the first random number seed.

[hippy]

All PICAXE random numbers will initialise to zero and follow the same sequence so all ( without any attempt to synchronise them ) will run in sync until small differences in oscillator frequencies causes them to drift apart. You will need a seed value which is different for each PICAXE programmed.

One way to create a seed is to read the initial value from Eeeprom, update it and write back. This way you get a different sequence at each power-up. Unfortunately all those powered up the same number of times will stay in sync.

You can get a random value from reading the LDR as Boriz suggests, and you could add this to a stored Eeprom value.

Eeprom 0,(0) ' Initial seed - All the same

StartProgram:
Read 0,w0 ' Read initial seed
ReadAdc10 1, brightness
w0 = w0 + brightness
Random w0
Write 0,w0 ' Save a new seed for next time
Do
: ' Rest of code
Loop

There are other ways to do it; you could read the LDR value and repeat 'RANDOM w0' however many times indicated and so forth.

Note that PICAXE-08 only have limited ADC capabilities; only 16 distinct levels. You may be better off with 08M.

[SilentScreamer]

Assuming you have an unused input could you record a few bits from a floating input pin and use this as the seed? I've not got a clue as to how well it would work though.

[Jeremy Leach]

Or perhaps just have the picaxes in two groups each group (flock/swarm?!) fed from a different power switch. Then manually switch each set on with manual delay between switching - I'd think this would ensure each display sequence would be sufficiently different??