Recommendations - Model Train Controller

[Acetronics2]

No secret, Malc ...

PWM freq too low.
( may be also a poor quality motor too ... but you can't choose which will be used.)

Alain

[malc-c]

No secret, Malc ...

PWM freq too low.
Alain

The max setting I can use seems to be 190 for freqency, 255 for resolution, with an OSC value of 20

[malc-c]

I've been trying to phathom out what I need to set ANSEL to or whats wrong with the code to get this to work 100%.

Referring to my post #74, I have three PWM outputs, but when I connect pot 4 to pin 10 and the corresponding output (pin 7 RC3) the loco just shoots off at full speed with no control - Here's the code

@ __CONFIG  _HS_OSC & _WDT_ON & _PWRTE_ON & _MCLRE_OFF 


     ;ANSEL = %00010111    - dt suggested value
ANSEL=%00110001     ; original 
CMCON=7
TRISA=%11111111        'set PORTA as all input 
TRISC=%00000001        'set PORTC as all output apart from RC0


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  190                ; SPWM Frequency
DEFINE SPWM_RES   255               ; 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]
  DutyVar4 VAR DutyVars[3]

ASM
SPWM_LIST  macro                    ; Define Pin's to use for SPWM
    SPWM_PIN  PORTC, 2, _DutyVar1   ; and the associated DutyCycle variables
    SPWM_PIN  PORTC, 5, _DutyVar2   ; Notice the underscore before variables
    SPWM_PIN  PORTC, 4, _DutyVar3
    SPWM_PIN  PORTC, 3, _DutyVar4
  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, DUTYVAR1
 ADCIN 1, DUTYVAR2
 ADCIN 2, DUTYVAR3
 ADCIN 4, DUTYVAR4
 GOTO Main

Here's hoping someone can point e in the right direction

[malc-c]

Ok I think I now understand the settings for ANSEL. Reading the datasheet again

ANSEL — ANALOG SELECT REGISTER (ADRESS: 91h) (PIC16F676 ONLY)

ANS7 ANS6 ANS5 ANS4 ANS3 ANS2 ANS1 ANS0
bit 7 bit 0
bit 7-0: ANS<7:0>: Analog Select between analog or digital function on pins AN<7:0>, respectively.
1 = Analog input. Pin is assigned as analog input.(1)
0 = Digital I/O. Pin is assigned to port or special function.

So if I wanted all analogue I set ANSEL to 11111111 - all digital 00000000

Ergo to set AN0, AN1, AN2 and AN4 Ansel should = 00010111, which is exactly what Darrel suggested. However when compiled with this setting the 4th output still runs at full speed with no control.

Could it be that the issue is with the declaration of the array - as it has [3] and I would assume that there are 4 channels so maybe this should be [4] ??

Could it be that the issue is with the declaration of the array - as it has [3] and I would assume that there are 4 channels so maybe this should be [4] ??

Looked like that was teh cause - I now have 4 working channels... just need to resolve the issue of the PIC locking on at full throttle and I'm done !

[Darrel Taylor]

Boy. Try to get some sleep, and people start talking to themselves.

Looks like the guy you were talking to, helped figure a couple things out though.

Good catch on the array size. Didn't see that.

Heard the video. That's just nasty sounding.
Is it any better yet after the changes?

I know you were told to change SPWM_RES to 255, but it really should be 256 for 8-bit resolution. Maybe the cause of the "PIC locking on at full throttle". I'll play with it here too and see.
<br>

[Darrel Taylor]

After further playing.

I can't make it "Lock".

Tried all 4 channels, tried 255/256 RES.

Incidently, 255 does work better. It's not the way I thought I wrote it. But...

That way 0 is always off, and 255 is always on.
<br>

[malc-c]

Darrel,

If using an LED its hard to make it lock. I think its either related to the power supply I'm using, or some other factor within the circuit as it does it on several loco's. I have a 0.1uf spread accros the power pins of the PIC, and power rails in a bid to decouple the supply. I've also tried changing the 1K base resistor between the NPn and PIC output as I though that the driver circuit may be drawing more than the 25ma the port can take, but that made no difference

Is the PWM outout a square wave, sawtooth or just spikes that are increased in frequency? I would like to stick with PWM as there is less heat to dissapate in the circuit and it provides far better slow starts than varible voltage type controllers. Maybe I should look at using a PIC with hardware PWM, like the 16F690 ??