Post by thread:[PIC]: percentage time reglage

Hi again piclisters ! I have a problem here: I'm trying to understand a methode for switching on and off one pic output respecting an input percentage proportion from 10% to 90% of a pre-programmed time value ( from 10 seconds to 10 minutes ). With other words: 10% from 10 seconds means 1 second on + 9 seconds off 10% from 10 minutes means 60 x ( 1 second on + 9 secons off) ... 90% from 5 minutes and 30 seconds means 33 x (9 seconds on + 1 second off) How I can define a common algorithm which fits on any time and any percentage ? Thank you in advance, Vasile -- http://www.piclist.com hint: To leave the PICList spam_OUTpiclist-unsubscribe-requestTakeThisOuTmitvma.mit.edu

On Mon, 1 Apr 2002 14:11:20 +0300, Vasile Surducan wrote: >Hi again piclisters ! > >I have a problem here: I'm trying to understand a methode for switching >on and off one pic output respecting an input percentage proportion from >10% to 90% of a pre-programmed time value ( from 10 seconds to 10 minutes >). With other words: >10% from 10 seconds means 1 second on + 9 seconds off >10% from 10 minutes means 60 x ( 1 second on + 9 secons off) >... But 10% from 600 seconds means 60 seconds on and 540 seconds off. :=) Unless there's some reason not to do it, your math will be a little more straightforward if you can do everything in seconds rather than mixing units. Regards, Bob -- http://www.piclist.com hint: To leave the PICList .....piclist-unsubscribe-requestKILLspam@spam@mitvma.mit.edu

> I have a problem here: I'm trying to understand a methode for switching > on and off one pic output respecting an input percentage proportion from > 10% to 90% of a pre-programmed time value ( from 10 seconds to 10 minutes > ). With other words: > 10% from 10 seconds means 1 second on + 9 seconds off > 10% from 10 minutes means 60 x ( 1 second on + 9 secons off) > ... > 90% from 5 minutes and 30 seconds means 33 x (9 seconds on + 1 > second off) > > How I can define a common algorithm which fits on any time and any > percentage ? This sounds simple if you rephrase it as a PWM output lasting for a specified time. Since your PWM period is 10 seconds, this is simple to do in software. If 10% resolution is enough, then you only need an interrupt every second to re-evaluate the PWM output. I think you already know this, Vasile, so what am missing? ***************************************************************** Embed Inc, embedded system specialists in Littleton Massachusetts (978) 742-9014, http://www.embedinc.com -- http://www.piclist.com hint: To leave the PICList piclist-unsubscribe-requestKILLspammitvma.mit.edu

> How I can define a common algorithm which fits on any time > and any percentage ? Hi Vasile, I'm looking at something very similar today. A PWM output that varies from 1:254 to 254:1 over an adjustable time- base. ie using a TMR0 interrupt it could be as short as few instruction cycles per "on" bit as possible right up to several milliseconds per "on" bit, all the time keeping the same ratio of off:on. IOW, the PWM can be altered as well as the overall frequency. Mine is a little more complicated than yours in that I want to have a "fine" and "coarse" adjustment (via pots) But enough about me - I'll be interested in any algorithms you find that might be applicable to what I'm doing. Could I suggest that you look at the two parameters separately - on:off ratio and "magnification" ratio. Determine a base unit of measurement, perhaps a timer interrupt, and use a RAM counter as the amount to scale the on:off times. There's a list of maths routines here http://www.piclist.com/techref/microchip/math/basic.htm I know % calculations have been discussed on the list. IIRC do your multiplication first, then the division (to minimise errors). In your case, perhaps not think in terms of percentages but "per hectamillages" ?? ie use 10,000-base (16-bit) rather than 100-base (8-bit). You would get finer resolution and smaller errors -- http://www.piclist.com hint: To leave the PICList .....piclist-unsubscribe-requestKILLspam.....mitvma.mit.edu

Thanks all guys ( Bob, Olin and Joe in mail receiving order ) As usual, language bariers have stopped me to put the right question. Bob, I need a finest resolution so every time the minimum period will be 10 seconds and no more, for 10 minutes and 10% I need to do 60 times 1 second on and 9 secons off. Olin and Joe, I'm using an internal RTC ( interrupt tmr0 based ) which is self running only in the task I need ( by activating or not the interrupts). There is no problem here, I'm using flags and semaphores. This RTC is used to display a decreasing time clock from 9.59 ( 9 minutes and 59 seconds ) to 0.00. The flow of that clock is permanent in the phase I'm talking about even the output command is not because in the same task I need to command an output nibble with the algorithm I was talking about. My ideea is to forget about the minutes and to read the seconds every time I want an output command. Then keeping the command ON a number of seconds equal with percentage/10 and OFF the number of seconds equal with ( 100 - percentage )/10 , should provide the output I need... But how to deal with a 0 second reading ( for example at 3.00 ) ? I could test the seconds and if are 0 to wait until are changing... I think this is the partial answer for my problem... there is an easyest way ? Thank you, Vasile On Mon, 1 Apr 2002, Olin Lathrop wrote: {Quote hidden}> > I have a problem here: I'm trying to understand a methode for switching > > on and off one pic output respecting an input percentage proportion from > > 10% to 90% of a pre-programmed time value ( from 10 seconds to 10 minutes > > ). With other words: > > 10% from 10 seconds means 1 second on + 9 seconds off > > 10% from 10 minutes means 60 x ( 1 second on + 9 secons off) > > ... > > 90% from 5 minutes and 30 seconds means 33 x (9 seconds on + 1 > > second off) > > > > How I can define a common algorithm which fits on any time and any > > percentage ? > > This sounds simple if you rephrase it as a PWM output lasting for a > specified time. Since your PWM period is 10 seconds, this is simple to do > in software. If 10% resolution is enough, then you only need an interrupt > every second to re-evaluate the PWM output. > > I think you already know this, Vasile, so what am missing? > > > ***************************************************************** > Embed Inc, embedded system specialists in Littleton Massachusetts > (978) 742-9014, http://www.embedinc.com > > -- > http://www.piclist.com hint: To leave the PICList > EraseMEpiclist-unsubscribe-requestspam_OUTTakeThisOuTmitvma.mit.edu > > -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

On Tue, 2 Apr 2002 09:40:04 +0300, Vasile Surducan wrote: >Thanks all guys ( Bob, Olin and Joe in mail receiving order ) >As usual, language bariers have stopped me to put the right question. > >Bob, I need a finest resolution so every time the minimum period will be >10 seconds and no more, for 10 minutes and 10% I need to do 60 times 1 >second on and 9 secons off. > Sorry, my misunderstanding. I didn't pick up on the minimum period requirement. BTW, after re-reading my earlier post, I wasn't really trying to be a smart-a$$ (even though it may have appeared that way.) Regards, Bob -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

On Mon, 1 Apr 2002, Bob Barr wrote: > On Tue, 2 Apr 2002 09:40:04 +0300, Vasile Surducan wrote: > > >Thanks all guys ( Bob, Olin and Joe in mail receiving order ) > >As usual, language bariers have stopped me to put the right question. > > > >Bob, I need a finest resolution so every time the minimum period will be > >10 seconds and no more, for 10 minutes and 10% I need to do 60 times 1 > >second on and 9 secons off. > > > > Sorry, my misunderstanding. I didn't pick up on the minimum period > requirement. BTW, after re-reading my earlier post, I wasn't really > trying to be a smart-a$$ (even though it may have appeared that way.) > No, it doesn't for me... sincerely regards, Vasile -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

Vasile Surducan <PICLISTspam_OUTmitvma.mit.edu> wrote: > I need a finest resolution so every time the minimum period will be 10 > seconds and no more, for 10 minutes and 10% I need to do 60 times 1 > second on and 9 secons off. Ah, ok... NOW I understand. I, too, was puzzled when I saw that question coming from you. Something like this should work; it is -- as so many things are -- a variation on the Bresenham line-drawing algorithm: ; Enter with duty-cycle (0-100) in DUTY. This routine uses a ; register called SWITCH which must not change between calls ; to the routine. Note that I'm assuming RADIX=DEC. TIMER_INTERRUPT: TSTF DUTY BNZ TESTSW MOVLW -1 MOVWF SWITCH TESTSW: BTFSS SWITCH,7 GOTO TURNON BCF OUTPUT_PIN GOTO FINISH TURNON: BSF OUTPUT_PIN MOVLW 100 SUBWF SWITCH FINISH: MOVF DUTY,W ADDWF SWITCH This will ALWAYS produce the minimum PWM period necessary for a particular duty-cycle. In other words, DUTY=50 will result in ON-OFF ON-OFF etc. and DUTY=10 will result in ON-OFF-OFF-OFF-OFF-OFF-OFF-OFF-OFF-OFF ON-OFF-OFF-OFF-OFF-OFF-OFF-OFF-OFF-OFF etc. -Andy === Andrew Warren - @spam@aiwKILLspamcypress.com === === Principal Design Engineer === Cypress Semiconductor Corporation -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

Thanks Andrew, I have solved the problem in the same time when I have asked the question You know what a good teacher said: "I have explained the problem to my students once, then twice and they don't understood, third time almost I have understood the problem but they still don't understood...What should I do with them ?" I have do it almost in the same fashion like you say here... but I was using 6 fixed time point comparations with the flowing seconds. Thanks for the tip. Vasile On Tue, 2 Apr 2002, Andrew Warren wrote: {Quote hidden}> Vasile Surducan <KILLspamPICLISTKILLspammitvma.mit.edu> wrote: > > > I need a finest resolution so every time the minimum period will be 10 > > seconds and no more, for 10 minutes and 10% I need to do 60 times 1 > > second on and 9 secons off. > > Ah, ok... NOW I understand. I, too, was puzzled when I saw that > question coming from you. > > Something like this should work; it is -- as so many things are -- > a > variation on the Bresenham line-drawing algorithm: > > ; Enter with duty-cycle (0-100) in DUTY. This routine uses a > ; register called SWITCH which must not change between calls > ; to the routine. Note that I'm assuming RADIX=DEC. > > TIMER_INTERRUPT: > > TSTF DUTY > BNZ TESTSW > > MOVLW -1 > MOVWF SWITCH > > TESTSW: > > BTFSS SWITCH,7 > GOTO TURNON > > BCF OUTPUT_PIN > GOTO FINISH > > TURNON: > > BSF OUTPUT_PIN > > MOVLW 100 > SUBWF SWITCH > > FINISH: > > MOVF DUTY,W > ADDWF SWITCH > > This will ALWAYS produce the minimum PWM period necessary for a > particular duty-cycle. In other words, DUTY=50 will result in > > ON-OFF > ON-OFF > etc. > > and DUTY=10 will result in > > ON-OFF-OFF-OFF-OFF-OFF-OFF-OFF-OFF-OFF > ON-OFF-OFF-OFF-OFF-OFF-OFF-OFF-OFF-OFF > etc. > > -Andy > > === Andrew Warren - RemoveMEaiwTakeThisOuTcypress.com > === > === Principal Design Engineer > === Cypress Semiconductor Corporation > > -- > http://www.piclist.com hint: PICList Posts must start with ONE topic: > [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads > > -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics