CMO module is available with a number of AVR MCUs. mikroPascal PRO for AVR provides library which simplifies using PWM HW Module.

  Important :

For better understanding of PWM module it would be best to start with the example provided in Examples folder of our mikroPascal PRO for AVR compiler. When you select a MCU, mikroPascal PRO for AVR automaticaly loads the correct PWM-16bit library, which can be verified by looking at the Library Manager. PWM library handles and initializes the PWM module on the given AVR MCU, but it is up to user to set the correct pins as PWM output, this topic will be covered later in this section.

Library Routines

• PWM16bit_Init
• PWM16bit_Change_Duty
• PWM16bit_Start
• PWM16bit_Stop

Predefined constants used in PWM-16bit library

  Note :

Not all of the MCUs have 16bit PWM, and not all of the MCUs have both Timer/Counter1 and Timer/Counter3. Sometimes, like its the case with ATmega168, MCU has only Timer/Counter1 and channels A and B. Therefore constants that have in their name Timer3 or channel C are invalid (for ATmega168) and will not be visible from Code Assistant. It is highly advisable to use this feature, since it handles all the constants (available) and eliminates any chance of typing error.

PWM16bit_Init

Prototype	procedure PWM16bit_Init(wave_mode : byte; prescaler : byte; inverted : byte; duty : word; timer : byte);
Returns	Nothing.
Description	Initializes the PWM module. Parameter wave_mode is a desired PWM-16bit mode. There are several modes included : PWM, Phase Correct, 8-bit PWM, Phase Correct, 9-bit PWM, Phase Correct, 10-bit Fast PWM, 8-bit Fast PWM, 9-bit Fast PWM, 10-bit Parameter prescaler chooses prescale value N = 1,8,64,256 or 1024 (some modules support 32 and 128, but for this you will need to check the datasheet for the desired MCU). Paremeter inverted is for choosing between inverted and non inverted PWM signal. Parameter duty sets duty ratio from 0 to TOP value (this value varies on the PWM wave mode selected). PWM signal graphs and formulas are shown below. The N variable represents the prescaler factor (1, 8, 64, 256, or 1024). The N variable represents the prescaler factor (1, 8, 64, 256, or 1024). PWM16bit_Init must be called before using other functions from PWM Library.
Requires	You need a CMO on the given MCU (that supports PWM-16bit). Before calling this routine you must set the output pin for the PWM (according to the datasheet): DDB1_bit = 1; // set PORTB pin 1 as output for the PWM-16bit This code example is for ATmega168, for different MCU please consult datasheet for the correct pinout of the PWM module or modules.
Example	Initialize PWM-16bit module: PWM16bit_Init(_PWM16_PHASE_CORRECT_MODE_8BIT, _PWM16_PRESCALER_16bit_8, _PWM16_NON_INVERTED, 255, _TIMER1);

PWM16bit_Change_Duty

PWM16bit_Change_Duty(300, _TIMER1_CH_A );

PWM16bit_Start

PWM16bit_Start(_TIMER1 );		// Starts the PWM-16bit module on Timer/Counter1	

PWM16bit_Start(_TIMER3 );		// Starts the PWM-16bit module on Timer/Counter3	

PWM16bit_Stop

PWM16bit_Stop(_TIMER1 );		// Stops the PWM-16bit module on Timer/Counter1	

PWM16bit_Stop(_TIMER3 );		// Stops the PWM-16bit module on Timer/Counter3	

Library Example

The example changes PWM duty ratio continually by pressing buttons on PORTC (0-3). If LED is connected to PORTB.1 or PORTB.2 ,you can observe the gradual change of emitted light. This example is written for ATmega168. This AVR MCU has only Timer/Counter1 split over two channels A and B. In this example we are changing the duty ratio on both of these channels.

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program PWM16bit_Test;

var current_duty : byte;
    current_duty1 : byte;

begin
  DDRC.B0 := 0;                    // Set PORTC pin 0 as input
  DDRC.B1 := 0;                    // Set PORTC pin 1 as input

  DDRC.B2 := 0;                    // Set PORTC pin 2 as input
  DDRC.B3 := 0;                    // Set PORTC pin 3 as input

  current_duty := 255;             // initial value for current_duty
  current_duty1 := 255;            // initial value for current_duty

  DDRB.B1 := 1;                    // Set PORTB pin 1 as output pin for the PWM (according to datasheet)
  DDRB.B2 := 1;                    // Set PORTB pin 2 as output pin for the PWM (according to datasheet)

  PWM16bit_Init(_PWM16_FAST_MODE_9BIT, _PWM16_PRESCALER_16bit_1, _PWM16_INVERTED, 255, 1);

  while TRUE do
    begin
    if (PINC.B0 <> 0) then    // Detect if PORTC pin 0 is pressed
        begin                                   
          Delay_ms(40);                             // Small delay to avoid deboucing effect
          Inc(current_duty);                        // Increment duty ratio
          PWM16bit_Set_Duty(current_duty);          // Set incremented duty
        end
      else
        if (PINC.B1 <> 0) then                   // Detect if PORTC pin 1 is pressed
          begin
            Delay_ms(40);                           // Small delay to avoid deboucing effect
            Dec(current_duty);                      // Decrement duty ratio
            PWM16bit_Set_Duty(current_duty);        // Set decremented duty ratio
          end
        else
          if (PINC.B2 <> 0) then                 // Detect if PORTC pin 2 is pressed
            begin
              Delay_ms(40);                         // Small delay to avoid deboucing effect
              Inc(current_duty1);                   // Increment duty ratio
              PWM16bit_Set_Duty(current_duty1);     // Set incremented duty
            end
          else
            if (PINC.B3 <> 0) then               // Detect if PORTC pin 3 is pressed
              begin
                Delay_ms(40);                       // Small delay to avoid deboucing effect
                Dec(current_duty1);                 // Decrement duty ratio
                PWM16bit_Set_Duty(current_duty1);   // Set decremented duty ratio
              end;

    end;

end.

HW Connection

PWM demonstration

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