adcin and HPWM

[lerameur]

HI

I have a program here, I guess it is somewhat working. I get a very erratic output, I need a steady frequency with a varying duty cycle. What I see on the scope is varying duty cycle frequency going in all direction, without me touching the circuit. I have set a pot on analog pin 1 . I can see the voltage varying from 0 to 5 with the multimeter , so this is working, I have a 47k on the MCLR pin and 22pF cap on the 20Mhz oscillator. Can somebody see the problem,
I may have gotten the initialization wrong or something like it
Thanks

INCLUDE "modedefs.bas" 'Includes supoprt for PicBasic language
@ DEVICE pic16F88, HS_OSC , CCPMX_ON
DEFINE OSC 20 'use external 20mhz crystal
PAUSE 100 ' start-up delay

'/////////////////////////
'// PIN configuration //
'/////////////////////////

DEFINE CCP1_REG PORTB 'Define output port of pulses out
DEFINE CCP1_BIT 3 'Define output port of pulses out
Define ADC_BITS 8 ' Set number of bits in result
Define ADC_CLOCK 3 ' Set clock source (3=rc)
Define ADC_SAMPLEUS 50 ' Set sampling time in uSec

CMCON = 7 ' Disable analog comparator
ANSEL = %00000010 ' set AN6 (RA1) as analog, others to digital
ADCON1.7 = 1 ' Right justified results... duh... really needed in 8 bits???
ADCON0 = %11000001 ' Configure and turn on A/D Module

TRISB = %00000000 ' Set PORTB to all output
TRISA = %11111111 ' Set PORTA to all input


'///////////////////////////////////////////////
'// Variable Declaration and initialization //
'///////////////////////////////////////////////

DutyCycle var byte 'Create adval to store result

'//////////////////////////
'// Program starts here //
'//////////////////////////

Mainloop:
ADCON0.2 = 1 'Start Conversion

ADCIN 1, DutyCycle 'analog pin 1 get the 8 bit result

HPWM 1,DutyCycle,10500

GOTO Mainloop
end

[skimask]

I have a program here, I guess it is somewhat working.

It's a start eh?

I get a very erratic output, I need a steady frequency with a varying duty cycle. What I see on the scope is varying duty cycle frequency going in all direction,

Are you sure it's actually the frequency varying and not the 'scope triggering at different points?

Do you have an LCD (or anything similar) that you can output the variable DUTYCYCLE to, so you can monitor it?
How about a small cap across the ADC input pin to smooth that out just a bit? Most pot's aren't exactly clean...
And try left justify...16F88 has a 10 bit ADC. PBP manual says 8 bit ADC results should be LEFT justified. Maybe a high sampling time.

[lerameur]

Ya thats it, ADCON1.7 = 0

works fine

thanks skimask

K

[skimask]

Ya thats it, ADCON1.7 = 0
works fine
thanks skimask
K

I'd still put a small cap across the A/D input you're using.
Might kill off any stray spikes you get from a dirty pot...

[lerameur]

Hi

works better with cap.
Although I still have problem with the HPWM. I decided to put a value in for the duty cycle, and I am not getting the right duty cycle out. I mean it is going from 10 to 80% to 50%, its all over the place:


INCLUDE "modedefs.bas" 'Includes supoprt for PicBasic language
@ DEVICE pic16F88, HS_OSC , CCPMX_ON
DEFINE OSC 20 'use external 20mhz crystal
PAUSE 100 ' start-up delay

'/////////////////////////
'// PIN configuration //
'/////////////////////////

DEFINE CCP1_REG PORTB 'Define output port of pulses out
DEFINE CCP1_BIT 3 'Define output port of pulses out
Define ADC_BITS 8 ' Set number of bits in result
Define ADC_CLOCK 3 ' Set clock source (3=rc)
Define ADC_SAMPLEUS 50 ' Set sampling time in uSec

CMCON = 7 ' Disable analog comparator
ANSEL = %00000010 ' set AN1 (RA1) as analog, others to digital
ADCON1.7 = 0 ' Right justified results... duh... really needed in 8 bits???
ADCON0 = %11000001 ' Configure and turn on A/D Module

TRISB = %00000000 ' Set PORTB to all output
TRISA = %11111111 ' Set PORTA to all input


'///////////////////////////////////////////////
'// Variable Declaration and initialization //
'///////////////////////////////////////////////

DutyCycle var byte 'Create adval to store result

'//////////////////////////
'// Program starts here //
'//////////////////////////

Mainloop:
ADCON0.2 = 1 'Start Conversion

ADCIN 1, DutyCycle 'analog pin 1 get the 8 bit result

HPWM 1,166,10800

GOTO Mainloop
end

[skimask]

Don't keep overwriting the duty cycle value. Just write it once and let it run unless it changes.
If you look at the datasheet, you'll see that a few things tend to reset themselves whenever the duty cycle register is written, thereby screwing up your duty cycle.