PWM Library

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

Important :

AVR MCUs require you to specify the module you want to use. To select the desired PWM, simply change the letter x in the prototype for a number from 1 to 2.
Number of PWM modules per MCU differs from chip to chip. Please, read the appropriate datasheet before utilizing this library.
For the XMEGA family of MCUs change the xn in the routine prototype with C0, C1, D0, D1, E0, E1, F0 or F1 (MCU dependent).
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.
mikroC PRO for AVR does not support enhanced PWM modules.

PWM_xn_Init
PWM_xn_Set_Duty
PWM_xn_Start
PWM_xn_Stop

PWMx_Init

Prototype

void PWMx_Init(unsigned short wave_mode, unsigned short prescaler, unsigned short inverted, unsigned short duty);

Returns

Nothing.

Description

Initializes the PWM module.

Parameters :

wave_mode: desired PWM mode (Phase Correct or Fast PWM depending on the chosen MCU).

Value Description

_PWM1_FAST_MODE Fast mode for PWM1

_PWM1_FAST_MODE_OCRA Fast mode for PWM1

_PWM1_PHASE_CORRECT_MODE Phase Correct mode for PWM1

_PWM1_PHASE_CORRECT_MODE_OCRA Phase Correct mode for PWM1

_PWM2_FAST_MODE Fast mode for PWM2

_PWM2_PHASE_CORRECT_MODE Phase Correct mode for PWM2

prescaler: 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).

Value Description

_PWM1_PRESCALER_1 Sets prescaler value to 1 (No prescaling).

_PWM1_PRESCALER_8 Sets prescaler value to 8.

_PWM1_PRESCALER_32 Sets prescaler value to 32.
This value is not available for every MCU, please consult appropriate datasheet.

_PWM1_PRESCALER_64 Sets prescaler value to 64.

_PWM1_PRESCALER_128 Sets prescaler value to 128.
This value is not available for every MCU, please consult appropriate datasheet.

_PWM1_PRESCALER_256 Sets prescaler value to 256.

_PWM1_PRESCALER_1024 Sets prescaler value to 1024.

_PWM2_PRESCALER_1 Sets prescaler value to 1 for the second PWM module.

_PWM2_PRESCALER_8 Sets prescaler value to 8 for the second PWM module.

_PWM2_PRESCALER_32 Sets prescaler value to 32 for the second PWM module.
This value is not available for every MCU, please consult appropriate datasheet.

_PWM2_PRESCALER_64 Sets prescaler value to 64 for the second PWM module.

_PWM2_PRESCALER_128 Sets prescaler value to 128 for the second PWM module.
This value is not available for every MCU, please consult appropriate datasheet.

_PWM2_PRESCALER_256 Sets prescaler value to 256 for the second PWM module.

_PWM2_PRESCALER_1024 Sets prescaler value to 1024 for the second PWM module.

inverted: inverted or non inverted PWM signal.

Value Description

_PWM1_INVERTED PWM1 inverted mode

_PWM1_NON_INVERTED PWM1 noninverted mode

_PWM2_INVERTED PWM2 inverted mode

_PWM2_NON_INVERTED PWM2 noninverted mode
duty: sets duty ratio from 0 to 255.

PWMx_Init must be called before using other functions from PWM Library.

Requires

You need a CMO on the given MCU (that supports PWM). Before calling this routine you must set the output pin for the PWM (according to the datasheet).

Example

Initialize PWM module:

PWM1_Init(_PWM1_FAST_MODE, _PWM1_PRESCALER_8, _PWM1_NON_INVERTED, 127);

PWM_xn_Init

Prototype

unsigned int PWM_xn_Init(unsigned long int freq_hz, unsigned short wave_mode);

Returns

Calculated timer period (value written in PER register) for XMEGA family of MCUs.

Description

Initializes the PWM module. Change the xn in the routine prototype with C0, C1, D0, D1, E0, E1, F0 or F1 (MCU dependent).

Parameters :

freq_hz: PWM frequency in Hz (refer to device datasheet for correct values in respect with Fosc).
wave_mode: desired PWM mode

Value Description

_PWM_SINGLE_SLOPE Single Slope Mode

_PWM_DUAL_SLOPE Dual Slope Mode

Requires

You need a CMO on the given MCU (that supports PWM). Before calling this routine you must set the output pin for the PWM (according to the datasheet).

Example

Initialize PWM module:

PWM_C0_Init(1000, _PWM_SINGLE_SLOPE);

PWMx_Set_Duty

Prototype

void PWMx_Set_Duty(unsigned short duty);

// for ATtiny441/481

void PWMx_Set_Duty(unsigned short duty, channel);

Returns

Nothing.

Description

Changes PWM duty ratio. Parameter duty takes values from 0 to 255, where 0 is 0%, 127 is 50%, and 255 is 100% duty ratio. Other specific values for duty ratio can be calculated as (Percent*255)/100.

Parameters :

duty: sets duty ratio from 0 to 255.
channel: set desired channel (only for ATtiny441/481). Valid values :

Value Description

_PWM1_CH_A Channel A

_PWM1_CH_B Channel B

Requires

PWM module must to be initialised (PWMx_Init) before using this function.

Example

PWM1_Set_Duty(192);

PWM_xn_Set_Duty

Prototype

void PWM_xn_Set_Duty(unsigned int duty_ratio, char inverted, char channel);

Returns

Nothing.

Description

Parameters :

duty_ratio: PWM duty ratio. Valid values: 0 to timer period returned by the PWM_xn_Init function.
inverted: inverted or non inverted PWM signal.

Value Description

_PWM_NON_INVERTED Non Inverted Mode

_PWM_INVERTED Inverted Mode

channel: PWM channel. Values :

Value Description

_CCA_CHANNEL CCA channel

_CCB_CHANNEL CCB channel

_CCC_CHANNEL CCC (this channel not available from PWM_x1_Set_Duty.

_CCD_CHANNEL CCD (this channel not available from PWM_x1_Set_Duty.

Requires

PWM module must to be initialised (PWM_xn_Init) before using this function.

Example

PWM_C0_Set_Duty(192,_PWM_NON_INVERTED,_CCC_CHANNEL);

PWMx_Start

Prototype	void PWMx_Start();
Returns	Nothing.
Description	Starts PWM.
Requires	MCU must have CMO module to use this library. PWMx_Init must be called before using this routine.
Example	PWM1_Start();

PWM_xn_Start

Prototype

void PWM_xn_Start(char channel);

Returns

Nothing.

Description

Starts PWM.

Parameters :

channel: Starts PWM at requested channel. Values :

Value Description

_CCA_CHANNEL CCA channel

_CCB_CHANNEL CCB channel

_CCD_CHANNEL CCC (this channel not available from PWM_x1_Start.

_CCD_CHANNEL CCD (this channel not available from PWM_x1_Start.

Requires

MCU must have CMO module to use this library.

PWM module must to be initialised (PWM_xn_Init) before using this function.

Example

PWM_C0_Start(_CCD_CHANNEL);

PWMx_Stop

Prototype	void PWMx_Stop();
Returns	Nothing.
Description	Stops the PWM.
Requires	MCU must have CMO module to use this library. PWMx_Init and PWMx_Start must be called before using this routine using this routine, otherwise it will have no effect as the PWM module is not running.
Example	PWM1_Stop();

PWM1_Enable

Prototype

void PWM1_Enable(unsigned short inverted, channel);

Returns

Nothing.

Description

Enables the PWM on desired channel.

Parameters :

inverted: PWM mode. Values :

Value Description

_PWM1_INVERTED PWM inverted mode

_PWM1_NON_INVERTED PWM non-inverted mode
channel: set desired channel. Valid values :

Value Description

_PWM1_CH_A Channel A

_PWM1_CH_B Channel B

Requires

MCU must have CMO module to use this library. PWMx_Init must be called before
using this routine otherwise it will have no effect as the PWM module is not running.

This routine is valid only for ATtiny441/481 MCUs.

Example

PWM1_Enable(_PWM1_NON_INVERTED, _PWM1_CH_A);

PWMxA_Enable

Prototype

void PWMxA_Enable(unsigned short inverted);

Returns

Nothing.

Description

Enables the PWM on channel A.

Parameters :

inverted: PWM mode. Values :

Value Description

_PWM1_INVERTED PWM1 module inverted mode

_PWM1_NON_INVERTED PWM1 module non-inverted mode

_PWM2_INVERTED PWM2 module inverted mode

_PWM2_NON_INVERTED PWM2 module non-inverted mode

Requires

MCU must have CMO module to use this library. PWMx_Init must be called before
using this routine otherwise it will have no effect as the PWM module is not running.

Example

PWM1A_Enable(_PWM1_NON_INVERTED);

PWMxB_Enable

Prototype

void PWMxB_Enable(unsigned short inverted, unsigned short modifyTop);

Returns

Nothing.

Description

Enables the PWM on channel B.

Parameters :

inverted: PWM mode. Values :

modifyTop: counter value. Values :

Value	Description
_PWM1B_TOP_VAL_OCRA	TOP value stored in the OCR0A Register (when using this value, channel A cannot be used).
_PWM1B_TOP_VAL_MAX	Maximal TOP value (255).
_PWM2B_TOP_VAL_OCRA	TOP value stored in the OCR0A Register (when using this value, channel A cannot be used).
_PWM2B_TOP_VAL_MAX	Maximal TOP value (255).

Requires

MCU must have CMO module to use this library. PWMx_Init must be called before
using this routine otherwise it will have no effect as the PWM module is not running.

Example

PWM1B_Enable(_PWM1_NON_INVERTED, _PWM1B_TOP_VAL_MAX);

PWM1_Disable

Prototype

void PWM1_Disable(unsigned short channel);

Returns

Nothing.

Description

Disables the PWM on desired channel .
Note that the timer counter will not be stopped by this function.

Parameters :

channel: set desired channel. Valid values :

Value Description

_PWM1_CH_A Channel A

_PWM1_CH_B Channel B

Requires

MCU must have CMO module to use this library. PWMx_Init must be called before
using this routine, otherwise it will have no effect as the PWM module is not running.

This routine is valid only for ATtiny441/481 MCUs.

Example

PWM1_Disable(_PWM1_CH_A);

PWMxA_Disable

Prototype	void PWMxA_Disable();
Returns	Nothing.
Description	Disables the PWM on channel A. Note that the timer counter will not be stopped by this function.
Requires	MCU must have CMO module to use this library. PWMx_Init must be called before using this routine, otherwise it will have no effect as the PWM module is not running.
Example	PWM1A_Disable();

PWMxB_Disable

Prototype	void PWMxB_Disable();
Returns	Nothing.
Description	Disables the PWM on channel B. Note that the timer counter will not be stopped by this function.
Requires	MCU must have CMO module to use this library. PWMx_Init must be called before using this routine, otherwise it will have no effect as the PWM module is not running.
Example	PWM1B_Disable();

PWMxA_Set_Duty

Prototype	void PWMxA_Set_Duty(unsigned short duty);
Returns	Nothing.
Description	Changes PWM duty ratio on channel A. Parameter `duty` takes values from 0 to 255, where 0 is 0%, 127 is 50%, and 255 is 100% duty ratio. Other specific values for duty ratio can be calculated as `(Percent*255)/100`. Parameters : `duty:` sets duty ratio from 0 to 255.
Requires	MCU must have CMO module to use this library. PWMx_Init and PWMx_Start must be called before using this routine using this routine, otherwise it will have no effect as the PWM module is not running.
Example	PWM1A_Set_Duty(192);

PWMxB_Set_Duty

Prototype	void PWMxB_Set_Duty(unsigned short duty);
Returns	Nothing.
Description	Changes PWM duty ratio on channel B. Parameter `duty` takes values from 0 to 255, where 0 is 0%, 127 is 50%, and 255 is 100% duty ratio. Other specific values for duty ratio can be calculated as `(Percent*255)/100`. Parameters : `duty:` sets duty ratio from 0 to 255.
Requires	MCU must have CMO module to use this library. PWMx_Init and PWMx_Start must be called before using this routine using this routine, otherwise it will have no effect as the PWM module is not running.
Example	PWM1B_Set_Duty(192);

PWM1_Set_Output

Prototype

void PWM1_Set_Output(unsigned short chOutputSelectA, chOutputSelectB);

Returns

Nothing.

Description

This routine sets TOCCn outputs for channels A and B. Valid only for ATtiny441/481 MCUs.

Parameters :

chOutputSelectA: TOCCn output for channel A. Valid values :

Value	Description
_PWM1_CH_A_OUT_TOCC1	Sets TOCC1 output for channel A
_PWM1_CH_A_OUT_TOCC3	Sets TOCC3 output for channel A
_PWM1_CH_A_OUT_TOCC5	Sets TOCC5 output for channel A
_PWM1_CH_A_OUT_TOCC7	Sets TOCC7 output for channel A
_PWM1_CH_A_OUT_NONE	Channel A will have no output.

chOutputSelectB: TOCCn output for channel B. Valid values :

Value	Description
_PWM1_CH_B_OUT_TOCC0	Sets TOCC0 output for channel B
_PWM1_CH_B_OUT_TOCC2	Sets TOCC2 output for channel B
_PWM1_CH_B_OUT_TOCC4	Sets TOCC4 output for channel B
_PWM1_CH_B_OUT_TOCC6	Sets TOCC6 output for channel B
_PWM1_CH_B_OUT_NONE	Channel B will have no output.

Requires

MCU must have CMO module to use this library. PWMx_Init must be called before
using this routine, otherwise it will have no effect as the PWM module is not running.

Example

PWM1_Set_Output(_PWM1_CH_A_OUT_TOCC1, _PWM1_CH_B_OUT_NONE);

PWM_xn_Stop

Prototype

void PWM_xn_Stop(char channel);

Returns

Nothing.

Description

Stops the PWM.

Parameters :

channel: Stops PWM at requested channel. Values :

Value Description

_CCA_CHANNEL CCA channel

_CCB_CHANNEL CCB channel

_CCC_CHANNEL CCC channel (this channel not available from PWM_x1_Stop.

_CCD_CHANNEL CCD channel (this channel not available from PWM_x1_Stop.

Requires

MCU must have CMO module to use this library. PWM_xn_Init and PWM_xn_Start must be called before
using this routine otherwise it will have no effect as the PWM module is not running.

Example

PWM_C0_Stop(_CCC_CHANNEL);

Library Example

The example changes PWM duty ratio on pin PB3 continually. If LED is connected to PB3, you can observe the gradual change of emitted light.

Copy Code To Clipboard

char current_duty;
char current_duty1;

void main(){

  DDB0_bit = 0;                   // Set PORTB pin 0 as input
  DDB1_bit = 0;                   // Set PORTB pin 1 as input

  DDC0_bit = 0;                   // Set PORTC pin 0 as input
  DDC1_bit = 0;                   // Set PORTC pin 1 as input

  current_duty  = 32;             // initial value for current_duty
  current_duty1 = 32;             // initial value for current_duty

  DDB3_bit = 1;                   // Set PORTB pin 3 as output pin for the PWM (according to datasheet)
  DDD7_bit = 1;                   // Set PORTD pin 7 as output pin for the PWM (according to datasheet)
  
  PWM1_Init(_PWM1_FAST_MODE, _PWM1_PRESCALER_8, _PWM1_NON_INVERTED, current_duty);
  PWM2_Init(_PWM2_FAST_MODE, _PWM2_PRESCALER_8, _PWM2_NON_INVERTED, current_duty1);

  do {
    if (PINB0_bit) {                            // Detect if PORTB pin 0 is pressed
      Delay_ms(40);                             // Small delay to avoid deboucing effect
      current_duty++;                           // Increment duty ratio
      PWM1_Set_Duty(current_duty);               // Set incremented duty
    }
    else
      if (PINB1_bit) {                          // Detect if PORTB pin 1 is pressed
        Delay_ms(40);                           // Small delay to avoid deboucing effect
        current_duty--;                         // Decrement duty ratio
        PWM1_Set_Duty(current_duty);             // Set decremented duty ratio
      }
      else
        if (PINC0_bit) {                        // Detect if PORTC pin 0 is pressed
          Delay_ms(40);                         // Small delay to avoid deboucing effect
          current_duty1++;                      // Increment duty ratio
          PWM2_Set_Duty(current_duty1);         // Set incremented duty
        }
        else
          if (PINC1_bit) {                      // Detect if PORTC pin 1 is pressed
            Delay_ms(40);                       // Small delay to avoid deboucing effect
            current_duty1--;                    // Decrement duty ratio
            PWM2_Set_Duty(current_duty1);       // Set decremented duty ratio
          }

  } while(1);                                   // Endless loop

}

HW Connection

PWM demonstration

Want more examples and libraries?
Find them on