Recommendations - Model Train Controller

[malc-c]

Alain, thanks for the life saving ring... its keeping me afloat

OK I have something that works... but its not as smooth as the PWM command in PBP.

This is the code, based on the sample taken from Darrel's website. Using a 12F675

@ __CONFIG _INTRC_OSC_NOCLKOUT & _WDT_ON & _PWRTE_ON & _MCLRE_OFF & _BODEN_ON

DEFINE OSC 4
CLEAR

DEFINE ADC_BITS 8	' Set number of bits in result
DEFINE ADC_CLOCK 3	' Set clock source (rc = 3)
DEFINE ADC_SAMPLEUS 50	' Set sampling time in microseconds

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

D var byte

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  GPIO, 0, _DutyVar1  ; and the associated DutyCycle variables
     SPWM_PIN  GPIO, 1, _DutyVar2  ; Notice the underscore before variables
     SPWM_PIN  GPIO, 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

;_____________________________________________________________________________

Main:                               
 ADCIN 0, D 
    DutyVar3 = D   
GOTO Main

The output is quite pulsed, and moving the pot produces rather stepped increase in brightness rather than a smooth increase. Also the range of the brightness is limited to 2/3 the travel of the POT (unlike when I used the PWM command when it was right across from one end to the other)

The waveform is different to that previously found when using the PWM command, as can be seen by the two images attached (one low, one high)

I assume the PWM settings in Darrels code can be changed by altering the values of

DEFINE SPWM_FREQ  40                ; SPWM Frequency
DEFINE SPWM_RES   256               ; SPWM Resolution

I'll play with the values and see if anything improves - Thanks for your help on this

EDIT:
Changing the OSC to 20 and freq to 100 gives less flicker, but the transitions are still not smooth... I also think that I need to come up with some driver circuit for the FET or feed the PIC outout into a Darlington pair arrangement with a power tranny reather than a FET