12F1572 PWM 16bit

[Mikam]

Resolved. Dry joint

---

Hi
Not getting any output on pin 5 ( PWM3). Pin 6 is cycling correctly.

;Chip Settings

chip 12F1572,32

config MCLR=ON

' GCB v98.04

Dir PORTA Out

#define HPWM16_3_Freq 100
#define HPWM16_3_Duty 50
HPWM16On ( 3 )

do Forever
set porta.1 on
wait 1 s
set porta.1 off
wait 1 s
loop
​```

[Anobium]

Sorry , but your code works here. I am getting a 100khz signal on Ra.2/pmw3

Check your config/chip.

Anobium

[Mikam]

Sorry. Appologies, found a dry joint on board.

[Mikam]

Hi
I am not able to get the resolution of 16bits, Could you just claify.

HPWM16On ( 3, 100, offsetFWD)

Offset forward being a word up to 65535, surely any value up to this would give a varied output.
I would like to use the output as a DC source, thru a 10kohm with a 10uF cap. I am only seeing resolution of around 1000.

[Anobium]

Please representive code. I can only guess what the code is.
Is offsetFWD a word? a byte?
Are you using #option explicit?

Keep the code short but representative.

Cheers

[Mikam]

#chip 12F1572,32
#config MCLR=ON
#option explicit

' GCB v98.04
dim offsetFWD as word

Dir PORTA.2 Out
dir porta.4 in
dir porta.5 in

 offsetFWD = 45000
 HPWM16On ( 3, 100, offsetFWD)

do Forever
   if porta.5=false then
      offsetFWD=offsetFWD+1
      if OffsetFWD>65500 Then
         offsetFWD=65500
      end if
       HPWM16(3, 100, offsetFWD)
      Wait 100 mS
   end if
   if porta.4=false then
      offsetFWD=offsetFWD-1
      if OffsetFWD<200 Then
         offsetFWD=200
      end if
       HPWM16(3, 100, offsetFWD)
      Wait 100 ms
   end if
loop
​

[Anobium]

Looks like a small issue with PWM16.

Please use a lower frequency, or, hand carft the regsisters.

My tests.

All the static code looks good, but, we he is passing variable at specific frequencies then I think things are not perfect.

My test code - this works. I get 10% but when I change the chip frequency 32mhz things are not correct.

#chip 12F1572, 4
#config mclr=on

Dir PORTA Out

HPWM16(3, 100, 6553 )   ' kHz, 10% duty cycle

do Forever
loop

#define USE_HPWM16_1 TRUE
#define USE_HPWM16_2 TRUE
#define USE_HPWM16_3 TRUE
#define USE_HPWM16_4 FALSE
#define USE_HPWM16_5 FALSE
#define USE_HPWM16_6 FALSE
#define USE_HPWM16_7 FALSE
#define USE_HPWM16_8 FALSE
#define USE_HPWM16_9 FALSE
#define USE_HPWM16_10 FALSE
#define USE_HPWM16_11 FALSE
#define USE_HPWM16_12 FALSE

***** Second program
This shows the issue. Works at 16 and not at 32. There may be an overflow issue somewhere.

#chip 12F1572, 16
#config mclr=on

Dir PORTA Out

' HPWM16(1, 10, 16384) '10 kHz, 25% duty cycle (16384/65535)
' HPWM16(2, 20, 16384) '20 kHz, 25% duty cycle (16384/65535)
HPWM16(3, 30, 16384) '30 kHz, 25% duty cycle (16384/65535)

porta.0 = 1
do Forever

  dim PMWValue, _value as long

  for PMWValue = 1 to 65536 step 64
          HPWM16(3, 100, PMWValue )
          wait 10 ms
  next
  porta.0 =!porta.0
  wait 20 ms
loop

[Anobium]

I adapted your code to get it respond a lot faster.
Pressing the button changes the duty cycle - starting at 65%

A slower frequency as a temp fix seems to work.

#chip 12F1572,16
#config MCLR=ON
#option explicit

' GCB v98.04
dim offsetFWD as word

Dir PORTA.2 Out
dir porta.4 in
dir porta.5 in

 offsetFWD = 45000
 HPWM16On ( 3, 100, offsetFWD)

do Forever
   if porta.5=false then
      offsetFWD=offsetFWD+100
      if OffsetFWD>65500 Then
         offsetFWD=65500
      end if
       HPWM16(3, 100, offsetFWD)
      Wait 100 mS
   end if
   if porta.4=false then
      offsetFWD=offsetFWD-100
      if OffsetFWD<200 Then
         offsetFWD=200
      end if
       HPWM16(3, 100, offsetFWD)
      Wait 100 ms
   end if
loop

[Mikam]

I was hoping to use full resolution of '1' increment/decrement.

[Anobium]

Looks to that you can. But, at the moment at slower chip frequency.

Are you saying you cannot?

[Mikam]

Even by changing to a lower frequency i am not getting the resolution. Looks as though resolution is set at 10bit.

[Anobium]

OK. When Pete has a look then he can look into that also.

Do you have any code that proes this? Like code that compares the 16bit registers and outputs to a serial terminal?

[Mikam]

I do not have more code. I am using a 6 1/2 digit DMM. Therefore 5V/65535=76.3uV
I am not seeing this change when incrementing/decrementing by 1.

[Anobium]

if you check the datasheet for capabilities of the 16 bit PMW, I will check the code for updating the register.

But, I am not sure that you will see the change per step on a DMM as you change the duty. But, I will check how the register is bwing set per step change.

[kent_twt4]

I played with the 12f1571 once upon a time, by manually manipulating the registers. I had it set up as an 8 bit PWM . I think all that would be required is to set the period register to PWM1PRH = 255 to make it a 16 bit. You could try it with different clock values, and see what you get?

The code might be something like this, not tested:
EDIT: whoops should use the load function to load buffers at the end of period.`

#chip 12f1572, 4
#define RedLed PortA.1
dim Red_PWM as Word Alias PWM1DCH, PWM1DCL
dim ramp as word
Call init_PWM

Do
  For ramp = 0 to 65535
    Red_PWM = ramp
    PWM1LDCON.LDA = 1
    wait 3 s
   next
Loop

Sub Init_PWM
'---- Red PWM1 ----
dir PORTA.1 in
PWM1PRH = 255
PWM1PRL = 255
PWM1CON = b'11010000' 'enable pwm and set POL bit for common anode
PWM1CLKCON = b'00000000'   '15.63kHz with PRL=255 4Mhz clk
PWM1PHH = 0
PWM1PHL = 0
PWM1DCH = 0
PWM1DCL = 0
PWM1LDCON.LDA = 1  'loads OFx, PHx, DCx, PRx buffers at end of period
dir PortA.1 out