Recommendations - Model Train Controller

[malc-c]

Darrel,

Sorry I missed that... I've remmed out the PWM line fro GPIO.0 and have got a reasonable result, especially for slow speed - The crawling speed of an 18 year old tank loco is really amaizing !!

Here's the code

DEFINE OSC 20
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  100                ; 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

Using a close loop fedback output stage and a 12v regulated supply for the track as per the diagram attached, I get a nice smooth slow speed control. This is using the 12F675 with its internal osc.

The loco does growl a bit when at really slow speed... and at maximum speed its fine for a goods train, but not an express. I susspect that using a higher track supply voltage will resolve the speed issue (my DVM reads 6.5v across the track at full speed), but wondered if there was anything I could do to reduce the growling at slow speed.

Please bear in mind that I'm still somewhat new to PICs and programming.. so If I've still overlooked something in the settings then please advise what I did wrong and how to correct it.