SPWM_INT - Multiple Software PWM Question

[RossWaddell]

Any idea why I get this ASM warning when compiling my code? I've included the snippet of code which I think is applicable, and the full code too.

' ***************************************************************
' Set up registers for PWM on CCP3 & 4
' ***************************************************************

; Use Mister E's MultiCalc to calculate PR2 value & hence Prescaler setting
; for T2CON:

; http://www.picbasic.co.uk/forum/content.php?r=159-New-PIC-Utility.-PICMultiCalc

; Can also use this web-based site:
; http://www.micro-examples.com/public/microex-navig/doc/097-pwm-calculator.html

CCP3CON = %00001100         ; Use CCP3 in PWM mode
CCP4CON = %00001100         ; Use CCP4 in PWM mode

;CCPTMRS = %00000000         ; Use Timer2 for all CCPs in PWM mode
                             ; (The default appears to be Timer2, so no need
                             ; to set it explicitly)
                             
T2CON   = %00000100         ; Timer2 on with 1:1 prescaler
PR2     = 249               ; For 16Mhz OSC the desired output of 16,000Hz is
                            ; achieved with this PR2 value (10-bit resolution
                            ; with 1:1 prescaler)

MinDuty CON 50              ; Lowest possible duty cycle at which motor spins
MaxDuty CON 1000            ; Maximum duty cycle available with PR2 = 249 and
                            ; 1:1 prescaler (According to Darrel:
                            ;      MaxDuty = (PR2 + 1) * 4

DutyVar3 VAR WORD
DutyVar4 VAR WORD

' Spin up motors to saved value of _MotorRPM
' (Below a cycle of MinDuty, the motors don't move at all)
FOR I = (MinDuty - 10) to MotorRPM
    DutyVar3  = I
    CCP3CON.4 = DutyVar3.0
    CCP3CON.5 = DutyVar3.1
    CCPR3L    = DutyVar3 >> 2

    IF PortEngDir = 0 THEN
        DutyVar4  = I
        CCP4CON.4 = DutyVar4.0
        CCP4CON.5 = DutyVar4.1
        CCPR4L    = DutyVar4 >> 2    
    ELSE
        DutyVar4  = (MaxDuty - I)
        CCP4CON.4 = DutyVar4.0
        CCP4CON.5 = DutyVar4.1
        CCPR4L    = DutyVar4 >> 2        
    ENDIF

    pause 33
NEXT I

Full PIC code:
PIC16F1825_Code.txt

[Darrel Taylor]

Those warnings aren't coming from the section you posted.

You are trying to use a value of 500 with byte sized EEPROM locations.

But I'm pretty sure you really want WORD sized EEPROM locations.
Change this ...

' ***************************************************************
' EEPROM Variables
' ***************************************************************

MotorRPM_Default   CON  500 ; half speed if max is 1000
EE_MotorRPM        DATA MotorRPM_Default
MotorRPM           VAR  BYTE
READ EE_MotorRPM, MotorRPM

PortEngDir_Default CON  0
EE_PortEngDir      DATA PortEngDir_Default
PortEngDir         VAR  BYTE
READ EE_PortEngDir, PortEngDir

... to this ...

' ***************************************************************
' EEPROM Variables
' ***************************************************************

MotorRPM_Default   CON  500 ; half speed if max is 1000
EE_MotorRPM        DATA WORD MotorRPM_Default
MotorRPM           VAR  WORD
READ EE_MotorRPM, WORD MotorRPM

PortEngDir_Default CON  0
EE_PortEngDir      DATA WORD PortEngDir_Default
PortEngDir         VAR  WORD
READ EE_PortEngDir, WORD PortEngDir

There are a few other WRITE statements in your program that need to be changed too.

[RossWaddell]

You're a life saver, Darrel - thanks. Updated the corresponding WRITE statements and all compiles fine (I didn't change the 'PortEngDir' stuff as that has only 2 values: 0 & 1)

Was there anything in the warning message which told you where to look?'

[Darrel Taylor]

Woops, I changed too much.

When I can't tell were an error is comming from, I go to the .LST file and search for the error or warning.
Ususally, the first error found in that file is the most important one.

It helps being able to read assembly language though.

[RossWaddell]

Being able to read assembly language would be helpful - I'm going to have to add that to the list of 'to-dos'.