Instant Interrupts - Revisited

[Darrel Taylor]

This is a series of include files that simplify the process of creating interrupt driven programs for PicBasic Pro. MPASM required.

Once you try this, you may never use ON INTERRUPT again.

Features:

Assembly language Interrupts
Basic language Interrupts
Both ASM and Basic interrupts in the same program
Service Multiple Interrupt sources
Prioritized execution order
Very easy to use


No ON INTERRUPT "Code Bloat"
No ON INTERRUPT " I'll service your interrupt whenever I feel like it." mentality.

.
One of the best things about this system, is that you don't have to remember where all the Enable bits and Interrupt flags are located.

Each interrupt "source" is given a unique name that is used to reference it.
The system "Looks Up" the correct bit locations for that name. Reducing those RTFM sessions to a minimum.
The following table lists the Named Interrupts.
Note: More interrupts have been added .. please visit http://darreltaylor.com/DT_INTS-14/intro.html

Available Interrupt Sources 14-bit

 INT_INT -- INT External Interrupt
 RBC_INT -- RB Port Change Interrupt
 TMR0_INT -- TMR0 Overflow Interrupt 16F
 TMR1_INT -- TMR1 Overflow Interrupt
 TMR2_INT -- TMR2 to PR2 Match Interrupt
 TX_INT -- USART Transmit Interrupt
 RX_INT -- USART Receive Interrupt
 CMP_INT -- Comparator Interrupt
 EE_INT -- EEPROM/FLASH Write Operation Interrupt
 BUS_INT -- Bus Collision Interrupt
 PSP_INT -- Parallel Slave Port Read/Write Interrupt
 AD_INT -- A/D Converter Interrupt
 SSP_INT -- Master Synchronous Serial Port Interrupt
 CCP1_INT -- CCP1 Interrupt
 CCP2_INT -- CCP2 Interrupt

Here's a simple example of toggling an LED using the external interrupt (INT). (Hello World)

LED1   VAR  PORTB.1

INCLUDE "DT_INTS-14.bas"     ' Base Interrupt System
INCLUDE "ReEnterPBP.bas"     ' Include if using PBP interrupts

ASM
INT_LIST  macro    ; IntSource,        Label,  Type, ResetFlag?
        INT_Handler    INT_INT,  _ToggleLED1,   PBP,  yes
    endm
    INT_CREATE               ; Creates the interrupt processor

    INT_ENABLE   INT_INT     ; enable external (INT) interrupts
ENDASM

Main:
  PAUSE 1
GOTO Main

'---[INT - interrupt handler]---------------------------------------------------
ToggleLED1:
     TOGGLE LED1
@ INT_RETURN

Code Size = 234 words

This project, and it's associated files, have been moved.
Please download them from my website.
DT_INTS-14 (12F-16F)
http://darreltaylor.com/DT_INTS-14/intro.html

DT_INTS-18 (18F)
http://darreltaylor.com/DT_INTS-18/home.html

.

[Darrel Taylor]

The ultimate overkill Blinky Light program ... using Timer 1

LED1   VAR  PORTB.1

INCLUDE "DT_INTS-14.bas"     ' Base Interrupt System
INCLUDE "ReEnterPBP.bas"     ' Include if using PBP interrupts

ASM
INT_LIST  macro    ; IntSource,        Label,  Type, ResetFlag?
        INT_Handler   TMR1_INT,  _ToggleLED1,   PBP,  yes
    endm
    INT_CREATE               ; Creates the interrupt processor
ENDASM

T1CON = $31                ; Prescaler=8, TMR1ON
@ INT_ENABLE  TMR1_INT     ; enable Timer 1 interrupts

Main:
  PAUSE 1
GOTO Main

'---[TMR1 - interrupt handler]--------------------------------------------------
ToggleLED1:
     TOGGLE LED1
@ INT_RETURN

Code Size = 240 words

OK, Why? ... You might ask.
Well, for one, this Blinky Light program will continue Blinking at the same rate, no matter what else you add to the Main: program loop. Try doing that with pauses.

[Darrel Taylor]

The NEW Elapsed Timer does, ... well .. it does exactly the same thing as the old Elapsed Timer. But now it works with the Instant Interrupt system. Which means that you can use many other interrupts in the same program without much trouble at all. Unlike the last version.

Here's an example of just the Elapsed Timer by itself.

INCLUDE "DT_INTS-14.bas"
INCLUDE "ReEnterPBP.bas"
INCLUDE "Elapsed_INT.bas"  ; Elapsed Timer Routines

ASM
INT_LIST  macro    ; IntSource,        Label,  Type, ResetFlag?
        INT_Handler   TMR1_INT,  _ClockCount,   PBP,  yes
    endm
    INT_CREATE            ; Creates the interrupt processor

    INT_ENABLE  TMR1_INT  ; Enable Timer 1 Interrupts  
ENDASM

GOSUB ResetTime           ' Reset Time to  0d-00:00:00.00
GOSUB StartTimer          ' Start the Elapsed Timer

Main:
  IF SecondsChanged = 1 THEN  
     SecondsChanged = 0
     LCDOUT $FE,2, DEC Days,"d-",DEC2 Hours,":",DEC2 Minutes,":",DEC2 Seconds
  ENDIF
GOTO Main

Code Size = 537 Words

This will create a Clock counting at 1/100 seconds. It runs in the background of PBP without any other program intervention required.

The time is kept in the variables:

    Ticks    var byte   ' 1/100th of a second
    Seconds  var byte   ' 0-59
    Minutes  var byte   ' 0-59
    Hours    var byte   ' 0-23
    Days     var word   ' 0-65535

The time can be easily displayed with a single line:

    LCDout $FE,2, dec Days,"d-",dec2 Hours,":",dec2 Minutes,":",dec2 Seconds

For each of the variables (Seconds, Minutes, Hours and Days) there is a flag
that indicates when the value of that variable has changed. The Flags are:

SecondsChanged var bit
MinutesChanged var bit
HoursChanged var bit
DaysChanged var bit

If you wanted to display the time like a clock, you could wait until
SecondsChanged = 1, display the time, then reset the flag.

    Loop1:
        if SecondsChanged = 1 then
           LCDout $FE,2, dec Days,"d-",dec2 Hours,":",dec2 Minutes,":",dec2 Seconds
           SecondsChanged = 0
        endif
    Goto Loop1

If you only wanted to display the time each minute instead of every second
just do the same thing using the MinutesChanged flag.

    Loop1:
        if MinutesChanged = 1 then
           LCDout $FE,2, dec Days,"d-",dec2 Hours,":",dec2 Minutes
           MinutesChanged = 0
        endif
    Goto Loop1

The timer can be Stopped and Started, like a stopwatch.

    Gosub StopTimer
    Gosub StartTimer

[Darrel Taylor]

So far I've shown one interrupt source being used at a time, but as I said in the first post, you can easily service Multiple Interrupt Sources.   So what if we wanted to join the previous 3 examples into one program.   NOT a problem!

To add more interrupt "Handlers", simply add them to the INT_LIST, and create a subroutine for them.

Since both the Blinky Light, and Elapsed Timer used TMR1, lets move the Blinky Light over to TMR0. Elapsed will still use TMR1.

LED1   VAR  PORTD.0
LED2   VAR  PORTD.1

INCLUDE "DT_INTS-14.bas"     ' Base Interrupt System
INCLUDE "ReEnterPBP.bas"     ' Include if using PBP interrupts
INCLUDE "Elapsed_INT.bas"    ' Elapsed Timer Routines

ASM
INT_LIST  macro    ; IntSource,        Label,  Type, ResetFlag?
        INT_Handler    INT_INT,  _ToggleLED1,   PBP,  yes
        INT_Handler   TMR0_INT,  _ToggleLED2,   PBP,  yes
        INT_Handler   TMR1_INT,  _ClockCount,   PBP,  yes
    endm
    INT_CREATE               ; Creates the interrupt processor

    INT_ENABLE   INT_INT     ; enable external (INT) interrupts
    INT_ENABLE  TMR0_INT     ; enable Timer 0 interrupts
    INT_ENABLE  TMR1_INT     ; Enable Timer 1 Interrupts  
ENDASM

OPTION_REG = OPTION_REG & $80 | 1  ; Set TMR0 Prescaler to 256, leave RBPU alone
GOSUB ResetTime              ' Reset Time to  0d-00:00:00.00
GOSUB StartTimer             ' Start the Elapsed Timer

Main:
    IF SecondsChanged = 1 THEN  
       SecondsChanged = 0
       LCDOUT $FE,$C0, DEC Days,"d-",DEC2 Hours,":",DEC2 Minutes,":",DEC2 Seconds
    ENDIF
GOTO Main

'---[INT - interrupt handler]---------------------------------------------------
ToggleLED1:
     TOGGLE LED1
@ INT_RETURN

'---[TMR0 - interrupt handler]-------------------------------(Blinky Light)------
T0Count  VAR WORD
ToggleLED2:
    T0Count = T0Count + 1
    IF T0Count = 512 THEN T0Count = 0 : TOGGLE LED2
@ INT_RETURN

<font size=-2>Code Size = 711 Words</font>

Now we have all three interrupt sources working together in the same program.

LED1 responds to the external INT
LED2 flashes, timed by TMR0
and, the elapsed timer is maintained via TMR1

And, all of this is happening behind the scenes of your normal PBP program.

[Darrel Taylor]

<table cellpadding=6><tr><td valign=center></td><td>The Instant Interrupt System consists of several "Layers".

The Bottom Layer is "DT_INTS-14.bas". This file contains everything required to use Interrupts at the ASM level. &nbsp; It handles all of the "Context Saving/Restoring", detects which interrupt has been triggered, and calls the appropriate "User Routine".

The next layer up is created from the INT_LIST macro you define in the program. &nbsp; It defines the Interrupt sources to use and the corresponding subroutines that will be called. &nbsp; They can be either simple subroutines, or complete "Modules" in a separate Include file, like the Elapse Timer. &nbsp; Up to 14 separate INT_Handler's can be in the LIST.

And, the Top Layer is the normal PBP program that runs in the foreground.

If Basic Laguage interrupts are not being used, then DT_INTS-14.bas is the only file you need to include.</td></tr></table>Here's another example of a Blinky Light program using TMR1 with an Assembly Language Interrupt handler

LED1   VAR  PORTD.0
LOW  LED1                    ; Set to Output Low

INCLUDE "DT_INTS-14.bas"     ; Base Interrupt System

ASM
INT_LIST  macro    ; IntSource,        Label,  Type, ResetFlag?
        INT_Handler   TMR1_INT,   ToggleLED1,   ASM,  yes
    endm
    INT_CREATE               ; Creates the interrupt processor

    INT_ENABLE  TMR1_INT     ; Enable Timer 1 Interrupts  
ENDASM

T1CON = $31                  ; Prescaler=8, TMR1ON

Main:
    PAUSE 1
GOTO Main

'---[TMR1_INT - interrupt handler]------------------------------------------
ASM
ToggleLED1
    btfsc  _LED1
    goto   $+3
    bsf    _LED1
    goto   $+2
    bcf    _LED1
    INT_RETURN
ENDASM

<font size=-3>Code Size = 104 Words</font>

Notice that the INT_Handler's Type is ASM, and the Label does not have an underscore before it.<hr><table cellpadding=6><tr><td></td><td valign=top>By using this type of Layering scheme. It allows us more flexability, depending on the type of interrupt we want to use. &nbsp; If we want to add Basic Language Handlers, all we need to do is Include "ReEnterPBP.bas", and it will insert another Layer in-between the Base and the Handlers.

With this layer included, you can have any combination of ASM and PBP interrupts in the same program</td></tr></table>
<br>

[Darrel Taylor]

October 05, 2002 was a good day. &nbsp; Because that's the day that Tim Box released his "INT_CTRL.pbp" program. &nbsp; The original "Instant Interrupts"

Tim had discovered that the only reason you couldn't use Basic statements in a normal interrupt, was because the PBP system variables currently being used by the statement that got interrupted, would be overwritten by the Basic statements in the interrupt routine. &nbsp; And that, all you have to do is save the state of the system vars at the start of the interrupt, and restore them back to the way they were before exiting the interrupt and you can use any Basic statements you want.

I've probably said it too many times already but ... Thanks again Tim!
<hr>
ReEnterPBP.bas is an adaptation of the same concept, but it allows the Interrupt system to determine if it needs to save the variables or not.

For instance, if you have a program with both ASM and PBP interrupt handlers, and an interrupt triggers an ASM handler, there's no need to save the variables first, it would just be waisting valuable time. And if more than 1 Basic handler is triggered at the same time, it only saves the variables once, and processes all the Interrupts on the same pass, before restoring the system vars, again saving time.

However, it does still take a lot of time to save all those variables. Usually it takes around 70 instruction cycles to save the vars. Then another 70 cycles to restore them again. At 4mhz it's 140us total save and restore time, which limits the maximum interrupt frequency to just over 7khz. At 20mhz OSC, you can go up to almost 36khz. That's fast enough to receive RS232 at over 250Kbaud with the USART. &nbsp; But is still considerably slower than you can get with ASM interrupts.

<br>

[Darrel Taylor]

<table><tr><td></td><td>While working on the 18F version, I discovered a bug in the ReEnterPBP file.
It was not restoring the RS1 and RS2 system variables properly.</td></tr></table>The file has been updated to version 3.2, and anyone using Instant Interrupts for the 14-bit PIC's should update the file as soon as possible.


<br>

[Darrel Taylor]

<table><tr><td></td><td>
At long last.

The Instant Interrupt system for 18F PIC's is now available.

It's become increasingly harder to keep things up to date here on the forum, so I've moved everything over to my website.
I'm still working on some of the pages, but everything you need is already there. It seems to take longer to make the web pages, than it does to write the program.

http://darreltaylor.com/DT_INTS-18/home.html</td></tr></table>

<br>

[Christopher4187]

Darrel,

Awesome program for a 18F4550. I never realized it takes so many lines of code just to blink an LED. Where can I adjust the duty cycle of the LED?

Thanks,

Chris

[Charles Linquis]

Many thanks to Darrel Taylor ! I'll have to try this immediately.


His techniques probably make most of what I'm about to write obsolete - but last night I promised that I would post what I learned about assembly-language interrupts and PBP from Tim Box, Charles Leo (of MELABS) and my own testing. The information presented is believed to be accurate, but I cannot guarantee this without complete testing - something I will do within the next few days. If I find any mistakes, I'll post an update.

1)
Some of the newer 18F parts have a new instruction -

RETFIE FAST

This instruction AUTOMATICALLY saves and restores the W,STATUS and BSR registers. Unless you mess around with pointers (such as FSR0x), this is all you need to do use. No extra instructions for saving and restoring context are needed. Just put it in place of the ordinary 'retfie' instruction. Check your datasheet to make sure if your part offers this. The 18F8720 and '8722 have this instruction.

2)
If your part does NOT have the "fast interrupt" enhancement, you should *normally* only need to save and restore W,STATUS and BSR.

3)
ALL of the variables declared by PBP but used in the assembly routine should be declared as 'bankA'.

4)
Variables declared by PBP are given an underscore "_" before the name when used in assembly. For example: 'MyVar var BYTE bankA' in PBP becomes '_MyVar' in assembly. To allow the same name in both PBP AND assembly, you need to define the variable as 'system' . For example 'MyVar BYTE bankA
system' has the name 'MyVar' in assembly (The assembler variable doesn't require an underscore as long as the variable is declared as 'system'.)

5)
Don't declare BIT variables in PBP to later be used in an assembly routine.
Use BYTE or WORD variables only. If you just need a bit to act as a flag, declare a PBP variable such as 'FLAGVAR' and set/reset one of the bits.

6)
Since your are only using the Access Bank (bankA) in your assembly-language routine, you don't need to use GOTOs. Use the BRA (branch) instruction instead.

7)
If you have two interrupt levels (high and low priority), you can use the PBP defines -
DEFINE INTHAND (label of high-priority interrupt handler) and
DEFINE INTLHAND (label of low-priority interrupt handler)

Save and restore context the same way as described above. RETFIE FAST works on the low-priority interrupt, too.

[SteveB]

RETFIE FAST works on the low-priority interrupt, too.

Just to clarify one important item. Here is snippet from the PIC18F8722 Datasheet under Memory Organization:

5.1.4 FAST REGISTER STACK
...
If both low and high priority interrupts are enabled, the
stack registers cannot be used reliably to return from
low priority interrupts. If a high priority interrupt occurs
while servicing a low priority interrupt, the stack register
values stored by the low priority interrupt will be
overwritten. In these cases, users must save the key
registers in software during a low priority interrupt.

So, more accurately, RETFIE FAST works when low-priority interrupts are enabled, as long as software saves & restores key registers during the low priority interrupts, and RETFIE FAST is only used to return from high-priority interrupts.

Steve

[Darrel Taylor]

Charles,

Well, you got 1 of them right. The other six get the game Buzzer. ennnhhh.

1) and 2)
All 18F's have shadow registers which store the key registers on any interrupt. As Steve already pointed out, if using High Priority Ints, you can't use the Shadow RAM for Low Priority Ints because they will be overwritten by a High Pri. Int. But since Low Pri. Ints can't interrupt High Pr. Ints, Shadow RAM is always valid for High Pri.

3) You can acces any variable in any bank of ram in an Int Handler. You just have to switch to that bank before using the variable. If you couldn't switch Banks in an interrupt handler, there wouldn't be a reason to save BSR at the beginning.

CHK?RP is the easiest way. There are some complicated issues with goto's and pbp's PREV_BANK variable. but once you figure out how it works. It's a piece of cake.

4) Correct.

5) They probably said to do BIT vars that way because PBP automatically puts BIT variables in alphabeticaly sorted order towards the end of used RAM. And since that's not BANKA, it didn't fit in with number 3). Switch the BANK, and you can access them too.

6) Again, BANKA is not a limitation.

7) Seven would have been ok except for the "RETFIE FAST works on the low-priority interrupt, too" which was covered in 1) and 2).

So, just use DT_INTS-18 with Basic Language Interrupts, and you don't have to worry about Any of that stuff. It's already handled for you.
<br>

[Darrel Taylor]

Chris,

For the examples, I simply used the timers overflow to TOGGLE a pin, so the duty cycle is always 50%. But then, it's just an example. If you increase the frequency of the timer Overflows, either by reducing the prescaler, or by re-loading the timer on each interrupt, or both, you can control the duty cycle within the interrupt handler. By incrementing a variable you can have it turn on for 10 interrupts and off for 246, or whatever resolution you want.
<br>

[Charles Linquis]

Darrel,

Thanks for the clarifications.

I'm not very familiar with bank switching, so at this time I didn't feel comfortable with dealing with that. You mention "CHK?RP" as an easy way to deal with the issue. I have no idea how to use this. I assume this is a macro that comes from somewhere. Could you please elaborate?

[mister_e]

CHK?RP is a PBP macro wich send you to the correct bank of a x register

CHK?RP PORTA

not much, using this one avoid you to read the x PIC datasheet to see where the x register is placed and do the bank switching yourself. Really handy stuff!

[Bruce]

Nice work Darrel.

[Darrel Taylor]

Bruce,

Thank You, Thank You, Thank You!

But I gotta ask.

Have you tried it yet?
Or does it just Look Cool?

Apprehensively,
&nbsp; Darrel

[Bruce]

Hi Darrel,

I've tested it on a Lab-X1 with 18F452. Timers 0, 1 and 3 hi-pri. USART rx
low-pri, and it works as advertised...;o}

P.S. I thought this was pretty slick;
movff FSR#v(F)L, fsave#v(F)Pr
movff FSR#v(F)H, fsave#v(F)Pr + 1

[Darrel Taylor]

Excellent!

Thanks for that.

And, yeah. The "Text Substitution" comes in pretty handy.
A bit Cryptic looking, but it is "Slick". Finding more uses for it with each new program.
<br>

[mister_e]

Darrel,
i'm developping an USB device to be release within let's say a year if everything work as expect. I have to use few interrupts source(4 as now.. but it grows). Today i decided to implement the instant interrupt in. All i can say is that it really reduce the latency. Worked well before... by far better now. You really save me to spend hours in the asm developpement...

Anyways i'll probably have no choice to use asm if i really don't want to move to the DsPIC. It's still in developpement so far.

Thanks!

[Darrel Taylor]

Sounds great Steve,

Were you using ON INTERRUPT before? or ASM?
<br>

[mister_e]

On interrupt first.. thereafter trying to do a real pure assembler ISR wich was a real improvement but didn't finished to implement/debug all of them 'cause you bum decide to stop me and release the 18Fs version and worst for FREE!

I may want to waste my time one day to do a pure asm ISR and compare both... but not for now as it's work really fine and i'm still unsure of the real final requirement 'round this device. You know how it is.. sometimes we see it bigger than it have to be

i'll keep you post anyways!

[b1arrk5]

I tried it, played with it for over three hours, nothing but compilation errors. I'm using Picbasic Pro 2.46 and MPASM 5.03. Any ideas?

[Darrel Taylor]

What were the errors?

And which example were you trying?
<br>

[Charles Linquis]

Darrel,

I finally had a chance to try DT_Ints-18, and it works (of course) as advertised. I can't thank you enough for working on this and finishing it just as I had a pressing need.

Keep up the good work!

Can I ask for HI2CREAD and HI2CWRITE next? Real FUNCTIONS?

[b1arrk5]

That was fast!

My errors are as follows,
Warning[230]c:\pbp\18f4550inc 20:_config has been deprecated for PIC18 devices. Use directive CONFIG. (this is listed five times, then,)
Error[128]c:\progra~1\Mecani~1\example2.asm 1150:missing arguement(s)
Error[113]c:\ "" 602: Symbol not previously defined (INTFLAGREG)
603: Symbol not previously defined (INTFLAGBIT)
218: " (INTFLAGREG)
218: " (INTFLAGBIT)
656: ERROR (INTERRUPT SOURCE (INTFLAGREG,INTFLAGBIT) NOT FOUND
713: ERRORINT_ENABLE - Priority State Not Found)

Thanks, I'm dying to try this out!

Jerry Gavin

[mister_e]

about the CONFIG warning error look at the FAQ
http://www.picbasic.co.uk/forum/showthread.php?t=543

Now be sure all files are in the same directory (source code, include and so on)

Still having problem? post your whole code here.

HTH

[mister_e]

Can I ask for HI2CREAD and HI2CWRITE next? Real FUNCTIONS?

what you mean by 'real function' ? unless using Macro and INCLUDE files and as far as i'm aware of, we can't add in the existing function list... i would be so much handy.

Darrel... Yet another Plug-In application

[b1arrk5]

When you have eliminated all possible problems, the only one left, no matter how improbable must be the solution, to paraphrase Sherlock Holmes. I noticed that two of the files that I downloaded were showing up as smaller than the file sizes listed on Darrel's site. I deleted them and downloaded again, and everything compiled perfectly the first time! Works Great! I had just received a few 18F4550s to play with so Darrel's timing was perfect.

Also, thanks to Steve for the note regarding the Config problem.

Thanks to all,

Jerry Gavin

[Darrel Taylor]

Jerry,

Great, I'm so glad you found it. Never would have figured that out from here.

Charles,

You're welcome,

I think the HI2C, and HI2CSLAVE should be pretty easy now with DT_INTS. As well as HSPI and HSPISLAVE, PSPSLAVE, SSPWM, Multi-SSPWM, PWPS, Multi-PWPS, etc. etc. etc.

However, in order to facilitate some of those types of commands, I think the next step is a universal FIFO (First In First Out) buffer structure. Already have it working, but it looks real ugly right now.

As for Functions, I think Steve's right. Until we can gain control over the compiler, or the IDE, or maybe create a Pre-compiler, Functions will remain on the PBP wish list.

DT

P.S. My "Timing" is still not perfect though, since I've been totally sidetracked from the Elapsed Timer/Oscillator accracy problem.
<br>

[Demon]

This is just so cool, this stuff is exactly what I needed to service USB without having to figure out how much to sprinkle within the code.

Can't wait to try this after dinner.

Robert

[Christopher4187]

Darrel,

You said "If you increase the frequency of the timer Overflows, either by reducing the prescaler, or by re-loading the timer on each interrupt, or both, you can control the duty cycle within the interrupt handler."

When I look at your program, I am completely lost. Can you tell me exactly what variable(s) I have to changed to get the LED blink faster or slower?

Thanks,

Chris

[Darrel Taylor]

Chris,

The prescaler can be changed with T1CON.
$31 = 1:8
$21 = 1:4
$11 = 1:2
$01 = 1:1

And the Timer is reloaded by putting values in TMR1H:TMR1L.

So first, decide what frequency you need, I'll go with 100hz.

Then, go to this thread...
Testing Forms [TimerCalc] Working I think?
http://www.picbasic.co.uk/forum/showthread.php?t=2031

Enter the OSC value you are using, say 20mhz.
I'll also go with 1:1 prescaler, enter that. (ok, it's already there)
Then enter 100 in the Freq field at the bottom.

Now you can see that it will take a total of 50,000 counts (ticks) to achieve 100hz.

Decide what resolution you want for the Duty-Cycle. ummm, 8-bit (256).

Now you just calculate the ON count from that with...
50000*DutyCycle/256 which is the same thing as...
50000*/DutyCycle in PBP
and the OFF count is 50000 - ONcount

Ok, so let's put that into the Blinky Light example

; Initialize your hardware first.


INCLUDE "DT_INTS-18.bas"     ' Base Interrupt System
INCLUDE "ReEnterPBP-18.bas"     ' Include if using PBP interrupts


LED1       VAR PORTB.1
DutyCycle  VAR BYTE


TotalCount CON 50000
ONcount    VAR WORD
OFFcount   VAR WORD


ASM
INT_LIST  macro    ; IntSource,        Label,  Type, ResetFlag?
        INT_Handler   TMR1_INT,  _ToggleLED1,   PBP,  yes
    endm
    INT_CREATE               ; Creates the interrupt processor
ENDASM


T1CON = $00                ; Prescaler=1:1, TMR OFF
@ INT_ENABLE  TMR1_INT     ; enable Timer 1 interrupts


Main:
    FOR DutyCycle = 0 TO 255           ; Ramp up
        GOSUB  SetDutyCycle
        PAUSE  5
    NEXT DutyCycle


    FOR DutyCycle = 254 TO 1 STEP -1   ; Ramp down
        GOSUB  SetDutyCycle
        PAUSE  5
    NEXT DutyCycle
GOTO Main




SetDutyCycle:
    ONcount = TotalCount*/DutyCycle
    OFFcount = TotalCount - ONcount
    IF DutyCycle = 0 THEN
        T1CON.0 = 0    ; turn off timer
        LOW  LED1      ; idle LOW
    ELSE
        T1CON.0 = 1    ; timer on if DutyCycle > 0
    ENDIF 
RETURN


DISABLE DEBUG
'---[TMR1 - interrupt handler]------------------------------------------------
@Timer1=TMR1L             ; map timer registers to a word variable
Timer1 VAR WORD EXT


ToggleLED1:
    IF LED1 THEN
        LOW LED1
        T1CON.0 = 0         ; stop the timer
        Timer1  = OFFcount  ; Load OFF count
        T1CON.0 = 1         ; start timer
    ELSE
        HIGH LED1
        T1CON.0 = 0         ; stop the timer
        Timer1  = ONcount   ; Load ON count
        T1CON.0 = 1         ; start timer
    ENDIF
@ INT_RETURN
ENABLE DEBUG

[Darrel Taylor]

OK, So once you try that, you'll realize that the RAMP is not linear.

It's more a function of the LED output than the PWM routine itself.

Changing it to 10-bit, and creating a lookup table that matches the LED brightness, seems to work. But I'm sure someone can come up with a better idea.
<br>

[Demon]

Darrel, if all goes well I hope to be able to commercialize this project within the next 57 years. Can I have your permission to include all this nice stuff within my code?

Hey, when I first started this project it was supposed to be nothing but a few switches and LEDs. That must have been over 2 years ago. Now I'm using a 320x240 graphic LCD, an 18F4550, two 16F628, 2 MCP23016, surface mount components, USB full speed, VB and eventually an Access database (I'm Tim The Toolman Taylor of home electronics).

Having to learn electronics kinda put me slightly behind schedule.

Robert
:lol:

[Darrel Taylor]

Hi Tim

If you do it in the next 57 days (or 5.7), you can still use everything to your hearts content.

Of course, you could add some routines to the pot.

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[Demon]

Thank you, thank you, thank you, thank you, thank you!
Thank you, thank you, thank you, thank you, thank you!

You can be sure that I will post anything useful that I can contribute; like the stuff for the SED1335 graphic LCD. Last time I Googled, there were no code examples for that one.

But I'm afraid there's not much I can add; you, Mister E and the other regulars have already covered anything I could conjure (and then some).

Robert

[Darrel Taylor]

But I'm afraid there's not much I can add;

Well, I'm no philosophy major, but I figure...

The Day you decide you Can't, is also the Day you won't.

Give it a try.
Added: or should I say more tries (examples). (SED1335 320x240 graphic LCD)

DT

Oh, and, You're Welcome, You're Welcome, You're Welcome,
You're Welcome, You're Welcome, You're Welcome.

[Charles Linquis]

Darrel,

I'm trying to work your Instant Interrupts in to my regular code.

When compiling, I get the following error messages:

WARNING:Unable to fit variable RetAddrH in requested bank 16
WARNING:Unable to fit variable RetAddrL in requested bank 16
WARNING:Unable to fit variable INT_Flags in requested bank 16
WARNING:Unable to fit variable HP_Vars in requested bank 0


Since these are just warnings, do I need to be concerned?
Is there a solution?

[Demon]

I'm the proud owner of an interupt routine in a PIC 16F628, my very first. It handles USART RX from a PIC 18F4550 wonderfully.

As mentionned on Darrel's information, I had to switch from MP to MPASM and encountered some delays in setting up the _CONFIG switches properly. But once I got that cleaned up I was up and running, this is just awesome!

(Charles, any chance you are using MP?)

Robert