Forum - MCS Electronics

 

FAQFAQ SearchSearch RegisterRegister Log inLog in

pwm with smoothly frequency and duty cycle with timer0

 
This forum is locked: you cannot post, reply to, or edit topics.   This topic is locked: you cannot edit posts or make replies.    www.mcselec.com Forum Index -> BASCOM-AVR Archive
View previous topic :: View next topic  
Author Message
mototest2

Bascom Member



Joined: 24 Dec 2006
Posts: 52

poland.gif
PostPosted: Fri Jul 11, 2014 10:54 am    Post subject: pwm with smoothly frequency and duty cycle with timer0 Reply with quote

Hi All

Please help me, I need make PWM with timer0 with adjusted frequency 0-250Hz and duty cycles 0-100%
with Timer1 all work good, but I must use timer0 and it don't work , can you help me ?


here is with TIMER1 :

Code:

Dim Duty_cycle_count As Long
Dim Frequency As Single
Dim Period As Single
Dim Timer_count As Long
Dim Duty_cycle As Byte
Const Timer_tick = 1000000000 / _xtal * 2

Tccr1a = &B01100011
Tccr1b = &B00010001
Config Portb.2 = output
Config Portb.1 = input
' in timer1 pinb.2 and b.1 are connected together

frequency = 180
duty_cycle = 50

do
call pwm_parameters
loop

sub pwm_parameters
Period = 1000000000 / Frequency
Timer_count = Period / Timer_tick
Tmp = Timer_count / 256
Ocr1ah = Tmp
Tmp = Timer_count Mod 256
Ocr1al = Tmp
Period = Timer_count * Duty_cycle
Duty_cycle_count = Period / 100

Compare1b = Duty_cycle_count

end sub
 


Thanks
Bob[/code]

(BASCOM-AVR version : 2.0.7.7 )
Back to top
View user's profile
EDC

Bascom Expert



Joined: 26 Mar 2014
Posts: 693

poland.gif
PostPosted: Fri Jul 11, 2014 8:25 pm    Post subject: Reply with quote

Used micro is important thing i this case Wink
Back to top
View user's profile Visit poster's website
mototest2

Bascom Member



Joined: 24 Dec 2006
Posts: 52

poland.gif
PostPosted: Fri Jul 11, 2014 8:29 pm    Post subject: Reply with quote

Atmega48
Back to top
View user's profile
EDC

Bascom Expert



Joined: 26 Mar 2014
Posts: 693

poland.gif
PostPosted: Wed Jul 16, 2014 4:16 pm    Post subject: Reply with quote

Sorry for long time for answear. My holidays with mor of % Very Happy ....This is even for Timer2 so if You don`t have done it yet I can help.
Back to top
View user's profile Visit poster's website
mototest2

Bascom Member



Joined: 24 Dec 2006
Posts: 52

poland.gif
PostPosted: Wed Jul 16, 2014 4:22 pm    Post subject: Reply with quote

I tried different method and don't work, must be timer0 not timer2 ,because I have free only pind.5 or pind.6
Back to top
View user's profile
EDC

Bascom Expert



Joined: 26 Mar 2014
Posts: 693

poland.gif
PostPosted: Wed Jul 16, 2014 8:48 pm    Post subject: Reply with quote

If I understand datasheet enough.. This config means : Mode 11,PWM Phase Correct, No prescale.
If Im not wrong then in Timer0 CompareB You can use only in CTC mode.
When for Timer1 ByteH and ByteL is used then for 8Bit timer propably..all must be recalculated.
Back to top
View user's profile Visit poster's website
EDC

Bascom Expert



Joined: 26 Mar 2014
Posts: 693

poland.gif
PostPosted: Thu Jul 17, 2014 9:17 am    Post subject: Reply with quote

I`m not profi with programming and steel learning but this is my little idea.



Code:
 Output_pin Alias Portb.5

Dim Freq As Word
Dim Freq_copy As Word
Dim Duty_cycle As Word
Dim Duty_copy As Word
Dim Timer_load As Byte
Dim Change_flag As Bit

' Timer0 in CTC mode, Freq and Duty must be calculated first
' for crystal

Do

If Output_pin = 1 Then

 Select Case Freq _copy

   Case 0
     Change_flag = 1
     Duty_copy = Duty_cycle
     If Duty_copy > 255 Then
     Timer_load = 255
     Duty_copy = Duty_copy - 255
     Else
     Timer_load = Duty_copy
     Duty_copy = 0
     End If

   Case Is < 255
     Timer_load = Freq_copy
     Freq_copy = 0

   Case Is > 255
    Timer_load = 255
    Freq_copy = Freq_copy - 255

  End Select

End If

If Output_pin = 0 Then

 Select Case Duty_copy

    Case 0

     Change_flag = 1
     Freq_copy = Freq
     If Freq_copy > 255 Then
     Timer_load = 255
     Freq_copy = Freq_copy - 255
     Else
     Timer_load = Freq_copy
     Freq_copy = 0

    Case Is < 255

     Timer_load = Duty_copy
     Duty_copy = 0

    Case Is > 255

     Timer_load = 255
     Duty_copy = Duty_copy - 255

  End Select
End If

Loop
End

'-------------------------------------

Timer0_isr:
Compare0a = Timer_load

If Change_flag = 1 Then
   Change_flag = 0
   Toggle Output_pin
End If
Return


I dont know is this fast enough and whats happend when value for freq or duty be close to 0. Today don`t have time for testing.
I forgot that Cases must be 0 - <255 - >255 and I fix it now.
Back to top
View user's profile Visit poster's website
Display posts from previous:   
This forum is locked: you cannot post, reply to, or edit topics.   This topic is locked: you cannot edit posts or make replies.    www.mcselec.com Forum Index -> BASCOM-AVR Archive All times are GMT + 1 Hour
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You cannot download files in this forum