How to blink 8 LEDs at different rates- concurrently?

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- 25th April 2010, 16:05
rmteo

How to blink 8 LEDs at different rates- concurrently?

To do the equivalent of the code below with each LED blinking at a different rate - except that all 8 LEDs must blink concurrently.

Code:

PORTB = 0 TRISB = 0 MAIN: LOOP1: TOGGLE PORTB.0 PAUSE 500 GOTO LOOP1 LOOP2: TOGGLE PORTB.1 PAUSE 220 GOTO LOOP2 LOOP3: TOGGLE PORTB.2 PAUSE 380 GOTO LOOP1 LOOP4: TOGGLE PORTB.3 PAUSE 750 GOTO LOOP4 LOOP5: TOGGLE PORTB.4 PAUSE 170 GOTO LOOP5 LOOP6: TOGGLE PORTB.5 PAUSE 400 GOTO LOOP6 LOOP7: TOGGLE PORTB.6 PAUSE 620 GOTO LOOP7 LOOP8: TOGGLE PORTB.7 PAUSE 130 GOTO LOOP8 GOTO MAIN
- 25th April 2010, 16:24
mackrackit

You want them all to come on at the same time and drop out at different rates?

Code:

PORTB = %11111111 PAUSE XXX PORTB = %11111110 PAUSE XXX PORTB = %11111100 ... LOOP OVER...

Something like that?
- 25th April 2010, 16:41
Melanie

Have as many LED's as you have pins...

Code:

LoopALED var BYTE LoopBLED var BYTE LoopCLED var BYTE LoopDLED var BYTE LoopELED var BYTE LoopFLED var BYTE LoopGLED var BYTE LoopHLED var BYTE ' LoopACON con 50 LoopBCON con 22 LoopCCon con 38 LoopDCon con 75 LoopECon con 17 LoopFCon con 40 LoopGCon con 62 LoopHCon con 13 ' TRISB=0 Loop: If LoopALED=0 then LoopALED=LoopACON Toggle PortB.0 else LoopALED=LoopALED-1 endif ' If LoopBLED=0 then LoopBLED=LoopBCON Toggle PortB.1 else LoopBLED=LoopBLED-1 endif ' If LoopCLED=0 then LoopCLED=LoopCCON Toggle PortB.2 else LoopCLED=LoopCLED-1 endif ' If LoopDLED=0 then LoopDLED=LoopDCON Toggle PortB.3 else LoopDLED=LoopDLED-1 endif ' If LoopELED=0 then LoopELED=LoopECON Toggle PortB.4 else LoopELED=LoopELED-1 endif ' If LoopFLED=0 then LoopFLED=LoopFCON Toggle PortB.5 else LoopFLED=LoopFLED-1 endif ' If LoopGLED=0 then LoopGLED=LoopGCON Toggle PortB.6 else LoopGLED=LoopGLED-1 endif ' If LoopHLED=0 then LoopHLED=LoopHCON Toggle PortB.7 else LoopHLED=LoopHLED-1 endif ' Pause 10 Goto Loop

Homework Done! Melanie's off down the pub...

Now repeat the above (excluding definitions) in less than 8 Lines of Code... (yes it can be done)!
- 25th April 2010, 19:34
rmteo

mack, the LEDs need to blink all at the same time, so that will not work.

Mel, use arrays and a for-next loop - along these lines?

Code:

Loop: for x = 0 to 7 If LoopLED[x] = 0 then LoopLED[x] = LoopCON[x] Toggle PORTB.x else LoopLED[x] = LoopLED[x]-1 endif next x Pause 10 Goto Loop
- 25th April 2010, 20:49
Melanie

Yes, pretty much, but I don't think PortB.x will work, so...

Code:

ShadowPortB=0 Loop: for x = 0 to 7 If LoopLED[x] = 0 then LoopLED[x] = LoopCON[x] ShadowPortB.0(x)=ShadowPortB.0(x)^1 else LoopLED[x] = LoopLED[x]-1 endif next x PortB=ShadowPortB Pause 10 Goto Loop

Where ShadowPort is a BYTE.
- 25th April 2010, 21:06
Darrel Taylor

Just to be different ...
And because she said "less than 8 Lines of Code" ... :)

Code:

TRISB = 0 Main: x = (x + 1) // 8 PORTB.0(x) = !(LoopLED(x) < LoopCON(x)) LoopLED(x) = (LoopLED(x) + 1) // (LoopCON(x) << 1) if x=7 THEN PAUSE 10 GOTO Main
- 26th April 2010, 03:19
Darrel Taylor

OUCH!

After running my loop in the SIM.
I realized the timing was Waaaayyyyy OFF.
Fortunately, the other examples were "OFF" too ... just not as far. :eek:

I've always said PAUSE is the worst statement in the BASIC language.
It got me again. :(

Here's a version that should compensate ...
It uses the CCP module in "Compare" mode to create a precise 10mS interval.
So when you give a delay value of 50, it actually takes 500mS, on the nose.

Sorry, it's more than 8 lines now. :o

Code:

DEFINE OSC 4 DEFINE BLINKYFREQ 100 ; 10mS periods DATA 50,22,38,75,17,40,62,13 ; default periods for each Output ;---------------------------------------------------------------- CCPR1val CON EXT : @CCPR1val = (OSC*1000000/4)/ BLINKYFREQ CCPR1 VAR WORD EXT : @CCPR1 = CCPR1L Timer1 VAR WORD EXT : @Timer1 = TMR1L CCPIF VAR PIR1.2 LoopLED VAR BYTE[8] LoopCON VAR BYTE[8] x VAR BYTE ;----[Initialize]------------------------------------------------ FOR x = 0 to 7 ; load the periods from EEPROM READ x, LoopCON(x) NEXT X ;-- setup CCP1 and Start Timer1 -- CCPR1 = CCPR1val ; set compare value CCP1CON = %00001011 ; compare mode, special event Timer1 = 0 ; clear Timer1 T1CON.0 = 1 ; start Timer1 TRISB = 0 ; PORTB all OUTPUT ;----[Main Program Loop]---------------------------------------- Main: x = (x + 1) // 8 PORTB.0(x) = !(LoopLED(x) < LoopCON(x)) LoopLED(x) = (LoopLED(x) + 1) // (LoopCON(x) << 1) IF x != 7 THEN Main Waiting: IF !CCPIF THEN Waiting CCPIF = 0 GOTO Main

Cheers,
- 26th April 2010, 07:43
Melanie

Personally, I'd have reduced PAUSE by a couple of clicks *smiles*
- 26th April 2010, 08:04
Mike, K8LH

Darrel, that algorithm is slick!

Does PBP allow assignments in expressions like C? For example;

Code:

while(1) { x = (x+1)&7; portb ^= ((!(LoopLED[x]=(LoopLED[x]+1)%LoopCON[x])) << x); delay_us(2500); }
- 26th April 2010, 08:59
Darrel Taylor

Thanks Mike.

Quote:

Originally Posted by Mike, K8LH

Does PBP allow assignments in expressions like C? ...

Nope, not even a +=

However, your x = (x+1)&7 takes much less time than my x = (x + 1) // 8 (Modulus) approach.
What was I thinking? :o

Cool, thanks!
- 26th April 2010, 09:24
keithdoxey

Quote:

Originally Posted by Darrel Taylor

Thanks Mike.

Nope, not even a +=

However, your x = (x+1)&7 takes much less time than my x = (x + 1) // 8 (Modulus) approach.
What was I thinking? :o

Cool, thanks!

DOH!!! The problem with working with so many different languages is that you can misread code. I took " //8 " to be a comment (Javascript style) that you were going to do it 8 times LOL
- 26th April 2010, 10:36
sayzer

If "8 lines" is about the loop part, then here is my code.

Think like a politician. Is is not less then 8?
:D

Code:

EEPROM 0,[50,22,38,75,17,40,62,13] 'RB0 - RB7 time intervals Time VAR BYTE[8] Timer VAR BYTE[8] Temp VAR BYTE Preload VAR WORD T1CON = %00000000 ' 1:1 @4Mhz TMR1IF VAR PIR1.0 ' An alias for overflow bit. TMR1ON VAR T1CON.0 Begin: Preload = 55543 'Timer1 preload value for excat 10ms. interval. FOR Temp = 0 TO 7 READ Temp ,Time[Temp] 'Fill time-intervals. Timer[Temp] = 0 'Clear timer array. NEXT Temp T: TMR1IF = 0 TMR1L = Preload.LowByte TMR1H = Preload.HighByte TMR1ON = 1 Start: IF TMR1IF THEN INT_TMR ' 1 line. GOTO Start INT_TMR: TMR1ON = 0 FOR Temp = 0 TO 7 IF Timer[Temp] = Time[Temp] THEN PORTB.0[Temp] = PORTB.0[Temp] ^1 Timer[Temp] = 0 ENDIF Timer[Temp] = Timer[Temp] + 1 NEXT Temp GOTO T END
- 26th April 2010, 19:25
rmteo

I am working on the skeleton of a generic task handler that will manage say 16 tasks concurrently. The LEDs are just simulating tasks that occur at set intervals. One of the tasks will be a seconds counter (with an interval of 1000mS) that is the basis of a RTC (good to the accuracy/stability of the HS crystal clock) and accurate timing is therefore an important concern. So using any kind of Pause or Delay function would not work.

Using a hardware timer is really the only way to do it. However, the timer also has to account for whatever time is used up by instruction cycles - which can vary depending on conditional branches and time spent in each task. DT's method of using a CCP in compare mode solves this problem nicely. Thanks.
- 26th April 2010, 22:39
Bruce

Have you seen this? http://www.microchipc.com/Hi-Tech_C_multitask/
- 26th April 2010, 23:47
rmteo

No I have not seen that link, thanks for pointing it out. I looked at Salvo and several other co-operative and pre-emptive RTOSes. Salvo is actually quite nice and has a small footprint. However, at $1,500 for a full-source license, it is somewhat pricey for my current needs - although it must be said that compared to some other commercial (particularly the pre-emptive ones such Avix, CMX, etc.) products, you could still call it a bargain. There are several free (and/or open source) pre-emptive systems for higher end devices but I find them extremely cumbersome to use and very resource hungry. The few that I looked at required about 20K ROM and 5-6K RAM for a useable configuration. I am also wanting something that can be easily ported to other devices/platforms (such as PIC24/dsPIC33 and 32-bit ARM Cortex M0/M3) and can be implemented using only a high level language (whether BASIC or C).

I have implemented what is basically a time-sliced task handler that will do 16 tasks in about 250 bytes of ROM and 75 bytes of RAM - additional tasks require 2 bytes of RAM per task. Small enough to run on a PIC12/16 - reducing the number of tasks could reduce the ROM (and RAM) footprint even further. Works fine - as I mentioned in a previous post, I have an application where an RTC is implemented using one of the tasks as an accurate seconds counter.