SPWM_INT - Multiple Software PWM
This program allows you to have MANY' Pulse Width Modulation's being generated as an interrupt driven Background process with PicBasic Pro.
Features:
* Multiple Slow Speed PWM outputs simultaneously on 1 chip, limited only by the processor speed, and SPWM frequency/resolution configuration.
* Works on just about any chip. 18F or 14-bit core's.
* Each SPWM output can be assigned to ANY General I/O pin on any Port
* PWM has a maximum resolution of 8-bit (0-255) 0=Always Low, 255=Always High, but lower resolutions are also available.
* It's an Include file, for easy implementation in your program.
* Some Error checking is built in, and supplies Messages detailing the problems. Although it won't find everything you can mess up.
As before: The downside to this program is that it uses a lot of processor time. This leaves very little for the rest of the program. Depending on how it is configured, it may use 75% or more of the available processing time. The reason it uses so much is due to the large number of interrupts required.
For instance, with a Frequency of 100hz, and a resolution of 256, it takes 25,600 interrupts per second. With each output using around 11 instructions per interrupt, it adds up to about 281,600 instructions per second, per output. Yowsa. Needless to say, you probably won't want to run this on a 4Mhz processor, although it is possible.
3 new features of this version are:
*SPWM outputs are defined with a Macro instead of with individual DEFINE's. This allows more outputs to be used if desired, and makes things much easier to work with.
*PWM resolution is no longer limited to 8-bit (256). If you only need 0-100%, you can simply specify the resolution with a DEFINE. This can GREATLY improve the performance by using MANY fewer interrupts.
*It is written to work with the Instant Interrupt system, and will work with either the 18F or 14-bit versions.
Here is a sample program that shows the basics of how to use SPWM_INT.
; Initialize your hardware first
DEFINE OSC 20
CLEAR
INCLUDE "DT_INTS-14.bas" ; Base Interrupt System
INCLUDE "SPWM_INT.bas" ; Software PWM module
DEFINE SPWM_FREQ 40 ; SPWM Frequency
DEFINE SPWM_RES 256 ; SPWM Resolution
DutyVars VAR BYTE[3] ; DutyCycle Variables
DutyVar1 VAR DutyVars[0] ; group them in an array for easy access
DutyVar2 VAR DutyVars[1] ; with FOR loops etc.
DutyVar3 VAR DutyVars[2]
ASM
SPWM_LIST macro ; Define Pin's to use for SPWM
SPWM_PIN PORTB, 0, _DutyVar1 ; and the associated DutyCycle variables
SPWM_PIN PORTB, 1, _DutyVar2 ; Notice the underscore before variables
SPWM_PIN PORTB, 2, _DutyVar3
endm
SPWM_INIT SPWM_LIST ; Initialize the Pins
ENDASM
ASM
INT_LIST macro ; IntSource, Label, Type, ResetFlag?
INT_Handler TMR1_INT, SPWMhandler, ASM, yes
endm
INT_CREATE ; Creates the interrupt processor
ENDASM
@ INT_ENABLE TMR1_INT ; enable Timer 1 interrupts
;_____________________________________________________________________________
RandVar VAR WORD : RandVar = 12345
LoopCount VAR WORD
Main: ; Simple Demo to fade/flash some LED's
DutyVar1 = 5 ; Start with 3 LED's at different
DutyVar2 = 50 ; brightness
DutyVar3 = 150
PAUSE 3000
FOR LoopCount = 1 TO 4 ; Reapeat 4 times
FOR DutyVar1 = 0 TO 150 ; Fade LED1 UP
PAUSE 10
RANDOM RandVar
DutyVar3 = RandVar & $3F ; Give LED3 a random dutycycle
NEXT DutyVar1
FOR DutyVar1 = 150 TO 0 STEP -1 ; Fade LED1 Down
PAUSE 10
RANDOM RandVar
DutyVar2 = RandVar & $3F ; Give LED2 a random dutycycle
NEXT DutyVar1
NEXT LoopCount
GOTO Main
This program will create 3 PWM channels on PORTB 0, 1, and 2. The PWM frequency is 40Hz, with a resolution of 256 (8-bit). All PWM channels automatically configure the pin as an output, and set the output to the LOW state. It will IDLE there until the Dutycycle is changed.
The Dutycycle can be changed at any time by simply changing the variable. The PWM output will be automatically updated (if necessary) on the next interrupt. There are no subroutines to call. It all "Just Happens".
DutyVar1 = 5 DutyVar2 = 50 DutyVar3 = 150
That's all there is to it.
Download the files here: (Right click and Save As) be sure to remove the .txt extension