12F683 and DT Instant Interrupts

[Darrel Taylor]

GOTO MAIN 'is this dangerous ?

Suicidal!

You will only get one interrupt that way, untill power is cycled or the GIE bit is set manually.

If you need to trigger processes in the main loop, you can set a Flag in the handler. Once it returns from the handler, the main loop can execute the required task where it can be interrupted again.

On 12F's and 16F's, you should NEVER gosub from the handler. There just aren't enough stack levels.

[mr.sneezy]

"Suicidal" I like it Darrel :-)
That word doesn't get used in code discussion much I'm sure...
OK, I just hit 'undo' on my code several times to stop myself needing to go slash my wrists ;-)

Flag. OK, if I understand correct I should set a flag variable in the int handler, then put my main code into a tight loop checking for it, then jump to my PPM output code when true, then back to the tight loop after clearing the flag...

There are a heap of ways to make a tight loop (If-then, While-wend, repeat-until). What would be the tightest (fastest) ? ASM ?

Martin

[Darrel Taylor]

There are a heap of ways to make a tight loop (If-then, While-wend, repeat-until). What would be the tightest (fastest) ? ASM ?

Anything that requires precise timing should be done in the handler, preferably in an ASM handler.

When it returns to the Main loop with a Flag set, the process it triggers should be able to do it, "whenever it gets around to it". There may be several things going on, and there's no guarantee when it will be processed.

If you're reading servo pulses, then the entire process of measuring the pulse should be done with the interrupts, and I don't mean sitting in a PULSIN statement in the handler. On the rising edge, start a timer. On the falling edge, stop the timer and collect the reading. Each time leaving the handler until the next condition occurs. Once you have a reading, then set a flag to let the main loop know to process the data. Now it has all the time in-between pulses to work on all those error rates, jitter etc and display them on the LCD at it's leisure.

[mr.sneezy]

Thanks Darrel,
In this part of the project (maybe the only part) I'm making the pulses, eight in a row for eight RC servo channels, of varying periods, rather than reading them. The TMR1 interrupt is just keeping the overall frame timing right.
Looking it now I think a tight loop reading the roll-over flag of the counter then doing the pulse train code would have worked just as well. I guess I thought that a real timer interrupt would minimise jitter in the total frame length.
Never mind, I'll carry on with the interrupt method now that I've started it.

I'd still like to see Alains code though.... Alain ?

Martin

[Acetronics2]

Hi, Martin

Darrel will love it, for sure !!! ( Lol ...)

'*****************************************************************************
'FRAMEGEN.BAS
'*****************************************************************************
'
' Générateur de Trame R/C Graupner/Multiplex sur 12F675
'
' 4,7,8 ou 9 Canaux - Neutre 1.5 ms
'
' Oscillateur interne 4 Mhz
'
' Trames déclenchées par interruptions TMR0 : PS = 1/128 Pl = 80
'
' Sortie sur GPIO.5
' Choix 4,7,8 ou 9 voies sur GPIO.3 et 4

'*****************************************************************************
'*****************************************************************************
'
@    __config _INTRC_OSC_NOCLKOUT & _WDT_ON & _PWRTE_ON & _MCLRE_OFF & _CP_OFF & _BODEN_ON


DEFINE OSC 4
DEFINE OSCCAL_1K 1
DEFINE INTHAND _Marker

ADCON0		= 0
ANSEL		= 0
CMCON		= 7

OPTION_REG	= %10000110     'Disable Pull-Ups - PSA = 128
INTCON		= %00100000		'TMR0 interrupt
PIE1		= 0
PIR1 		= 0

'*****************************************************************************
' Constantes

Mark 	CON 400
Reload 	CON 80
Neutral CON 1500
GR		CON 8
MPX		CON 9

'*****************************************************************************
' Variables


PROGRAM		var byte
PROGRAMOLD	var byte

FRAME4		var bit
FRAME7		var bit
FRAME8		var bit		

CLEAR

'*****************************************************************************
' I/Os

GPIO 		=%00100000	'GPIO.5 = 1 at startup
TRISIO 		=%00011000  'set GPIO3 GPIO4 as input GPIO.5 as Output

'*****************************************************************************

GOTO INIT

'*****************************************************************************
'*****************************************************************************
Marker: ' Interruption - Génération de la trame

TMR0 = Reload

GPIO.5 	= 0
PAUSEUS	Mark

GPIO.5 	= 1				' Voie 1
PAUSEUS 696

GPIO.5 = 0
PAUSEUS Mark

GPIO.5 	= 1				' Voie 2
PAUSEUS 796

GPIO.5 = 0
PAUSEUS Mark

GPIO.5 	= 1				' Voie 3
PAUSEUS 896

GPIO.5 = 0
PAUSEUS Mark

GPIO.5 	= 1				' Voie 4
PAUSEUS 992

IF FRAME4 THEN Selection

@ NOP
GPIO.5 = 0
PAUSEUS Mark

GPIO.5 	= 1				' Voie 5 - 1500µS
PAUSEUS 1096

GPIO.5 = 0
PAUSEUS Mark

GPIO.5 	= 1				' Voie 6
PAUSEUS 1196

GPIO.5 = 0
PAUSEUS Mark

GPIO.5 	= 1				' Voie 7
PAUSEUS 1290

IF FRAME7 THEN Selection

@ NOP
GPIO.5 = 0
PAUSEUS Mark

GPIO.5 	= 1				' Voie 8
PAUSEUS 1392

IF FRAME8 THEN Selection

@	NOP
GPIO.5 = 0
PAUSEUS Mark

GPIO.5 	= 1				' Voie 9
PAUSEUS 1496

Selection:

GPIO.5 = 0
PAUSEUS Mark

GPIO.5 = 1

'*****************************************************************************
'Lecture des Jumpers

PROGRAM = GPIO & %00011000

IF PROGRAMOLD <> PROGRAM THEN INIT

'*****************************************************************************
Start: 'Fin d'Interruption

INTCON.2 = 0
INTCON.7 = 1

'*****************************************************************************
CYCLE: 'Boucle de fonctionnement

WHILE 1
WEND

'*****************************************************************************
INIT: 'Lecture des Jumpers

PROGRAM = GPIO & %00011000

SELECT CASE Program

	CASE 24
	
		FRAME4 = 1 : FRAME7 = 0 : FRAME8 = 0
		
	CASE 16
	
		FRAME4 = 0 : FRAME7 = 1 : FRAME8 = 0
		
	CASE 8
	
		FRAME4 = 0 : FRAME7 = 0 : FRAME8 = 1
		
	CASE ELSE
	
		FRAME4 = 0 : FRAME7 = 0 : FRAME8 = 0
		
END SELECT

PROGRAMOLD = PROGRAM

GOTO Start

END

If you want to have variable pulse length... just inc or dec the PAUSEUS value before the "START" Label


And ... if you find something strange ... it is NOT an error !!!

( I told you Darrel would love it ....)

Alain

[Darrel Taylor]

Love comes in many forms ...

I'm still looking for the one that applies here.

Ummm, I found something strange ...
<br>

[Acetronics2]

Love comes in many forms ...

I'm still looking for the one that applies here.

Ummm, I found something strange ...
<br>

Hi, Darrel,

Really ???

I'm so surprised ... Something missing, may be ???

Regards
Alain