PWM 16 bit Library

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

Important :

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.

Predefined constants used in PWM-16bit library

The following variables are used in PWM-16bit library functions:	Description :
`_PWM16_PHASE_CORRECT_MODE_8BIT`	Selects Phase Correct, 8-bit mode.
`_PWM16_PHASE_CORRECT_MODE_9BIT`	Selects Phase Correct, 9-bit mode.
`_PWM16_PHASE_CORRECT_MODE_10BIT`	Selects Phase Correct, 10-bit mode.
`_PWM16_FAST_MODE_8BIT`	Selects Fast, 8-bit mode.
`_PWM16_FAST_MODE_9BIT`	Selects Fast, 9-bit mode.
`_PWM16_FAST_MODE_10BIT`	Selects Fast, 10-bit mode.
`_PWM16_PRESCALER_16bit_1`	Sets prescaler value to 1 (No prescaling).
`_PWM16_PRESCALER_16bit_8`	Sets prescaler value to 8.
`_PWM16_PRESCALER_16bit_64`	Sets prescaler value to 64.
`_PWM16_PRESCALER_16bit_256`	Sets prescaler value to 256.
`_PWM16_PRESCALER_16bit_1024`	Sets prescaler value to 1024.
`_PWM16_INVERTED`	Selects the inverted PWM-16bit mode.
`_PWM16_NON_INVERTED`	Selects the normal (non inverted) PWM-16bit mode.
`_TIMER1`	Selects the Timer/Counter1 (used with PWM16bit_Start and PWM16bit_Stop.
`_TIMER3`	Selects the Timer/Counter3 (used with PWM16bit_Start and PWM16bit_Stop.
`_TIMER1_CH_A`	Selects the channel A on Timer/Counter1 (used with PWM16bit_Change_Duty).
`_TIMER1_CH_B`	Selects the channel B on Timer/Counter1 (used with PWM16bit_Change_Duty).
`_TIMER1_CH_C`	Selects the channel C on Timer/Counter1 (used with PWM16bit_Change_Duty).
`_TIMER3_CH_A`	Selects the channel A on Timer/Counter3 (used with PWM16bit_Change_Duty).
`_TIMER3_CH_B`	Selects the channel B on Timer/Counter3 (used with PWM16bit_Change_Duty).
`_TIMER3_CH_C`	Selects the channel C on Timer/Counter3 (used with PWM16bit_Change_Duty).

Note :

Code Assistant

PWM16bit_Init

Prototype	void PWM16bit_Init(unsigned short wave_mode, unsigned short prescaler, unsigned short inverted, unsigned short duty, unsigned int timer);
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, 1);

PWM16bit_Set_Duty

Prototype

void PWM16bit_Set_Duty(unsigned duty, unsigned short channel);

Returns

Nothing.

Description

Sets PWM duty ratio. Parameter duty takes values shown on the table below. Where 0 is 0%, and TOP value is 100% duty ratio. Other specific values for duty ratio can be calculated as (Percent*TOP)/100.

Timer/Counter Mode of Operation :	TOP :	Update of OCRnX at :	TOVn Flag Set on :
PWM, Phase Correct, 8 bit	0x00FF	TOP	BOTTOM
PWM, Phase Correct, 9 bit	0x01FF	TOP	BOTTOM
PWM, Phase Correct, 10 bit	0x03FF	TOP	BOTTOM
Fast PWM, 8 bit	0x00FF	TOP	TOP
Fast PWM, 9 bit	0x01FF	TOP	TOP
Fast PWM, 10 bit	0x03FF	TOP	TOP

Requires

PWM module must to be initialised (PWM16bit_Init) before using PWM_Set_Duty function.

Example

Example lets set duty ratio to :

PWM16bit_Set_Duty(300, _TIMER1_CH_A );

PWM16bit_Enable

Prototype

void PWM16bit_Enable(unsigned short inverted, unsigned short channel);

Returns

Nothing.

Description

Enables PWM module on desired timer/channel.

Parameters :

inverted: PWM mode. Values :

Value Description

_PWM16_INVERTED PWM inverted mode

_PWM16_NON_INVERTED PWM non-inverted mode

channel: set desired channel. Valid values :

Value Description

_PWM16_TIMER1_CH_A Timer1, Channel A

_PWM16_TIMER2_CH_A Timer2, Channel B

_PWM16_TIMER1_CH_B Timer1, Channel A

_PWM16_TIMER2_CH_B Timer2, Channel B

Requires

PWM module must to be initialised (PWM16bit_Init) before using this routine.

Example

PWM16bit_Enable(_PWM16_NON_INVERTED, _PWM16_TIMER1_CH_A );

PWM16bit_Disable

Prototype

void PWM16bit_Disable(unsigned short channel);

Returns

Nothing.

Description

Disables PWM module on desired timer/channel.

Parameters :

channel: set desired channel. Valid values :

Value Description

_PWM16_TIMER1_CH_A Timer1, Channel A

_PWM16_TIMER2_CH_A Timer2, Channel B

_PWM16_TIMER1_CH_B Timer1, Channel A

_PWM16_TIMER2_CH_B Timer2, Channel B

Requires

PWM module must to be initialised (PWM16bit_Init) before using this routine.

Example

PWM16bit_Disable(_PWM16_TIMER1_CH_A );

PWM16bit_Set_Output

Prototype

void PWM16bit_Set_Output(unsigned short timer, chOutputSelectA, chOutputSelectB);

Returns

Nothing.

Description

This routine sets PWM module output on desired timer/channel.

Parameters :

timer: set desired timer. Valid values :

Value Description

_PWM16_TIMER1 Timer1

_PWM16_TIMER2 Timer2

chOutputSelectA: TOCCn output for channel A. Valid values :

Value	Description
_PWM16_CH_A_OUT_TOCC1	Sets TOCC1 output for channel A
_PWM16_CH_A_OUT_TOCC3	Sets TOCC3 output for channel A
_PWM16_CH_A_OUT_TOCC5	Sets TOCC5 output for channel A
_PWM16_CH_A_OUT_TOCC7	Sets TOCC7 output for channel A
_PWM16_CH_A_OUT_NONE	Channel A will have no output.

chOutputSelectB: TOCCn output for channel B. Valid values :

Value	Description
_PWM16_CH_B_OUT_TOCC0	Sets TOCC0 output for channel B
_PWM16_CH_B_OUT_TOCC2	Sets TOCC2 output for channel B
_PWM16_CH_B_OUT_TOCC4	Sets TOCC4 output for channel B
_PWM16_CH_B_OUT_TOCC6	Sets TOCC6 output for channel B
_PWM16_CH_B_OUT_NONE	Channel B will have no output.

Requires

PWM module must to be initialised (PWM16bit_Init) before using this routine.

Example

PWM16bit_Set_Output(_PWM16_TIMER1, _PWM16_CH_A_OUT_TOCC1, _PWM16_CH_B_OUT_TOCC0);

PWM16bit_Start

Prototype	void PWM16bit_Start(unsigned int timer);
Returns	Nothing.
Description	Starts PWM-16bit module with alredy preset values (wave mode, prescaler, inverted and duty) given in the PWM16bit_Init.
Requires	MCU must have CMO module to use this library. PWM16bit_Init must be called before using this routine, otherwise it will have no effect as the PWM module is not initialised.
Example	PWM16bit_Start(_TIMER1 ); // Starts the PWM-16bit module on Timer/Counter1 or PWM16bit_Start(_TIMER3 ); // Starts the PWM-16bit module on Timer/Counter3

PWM16bit_Stop

Prototype	void PWM16_Stop(unsigned int timer);
Returns	Nothing.
Description	Stops the PWM-16bit module, connected to Timer/Counter set in this stop function.
Requires	MCU must have CMO module to use this library. Like in PWM16bit_Start before, PWM16bit_Init must be called before using this routine , otherwise it will have no effect as the PWM module is not running.
Example	PWM16bit_Stop(_TIMER1 ); // Stops the PWM-16bit module on Timer/Counter1 or 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.B1 or PORTB.B2 ,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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char current_duty;
char current_duty1;

void main(){

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

  DDC2_bit = 0;                   // Set PORTC pin 2 as input
  DDC3_bit = 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);

  do {
    if (PINC.B0) {                             			// Detect if PORTC pin 0 is pressed
      Delay_ms(40);                             			// Small delay to avoid deboucing effect
      current_duty++;                           			// Increment duty ratio
      PWM16bit_Change_Duty(current_duty, _TIMER1_CH_A);       		// Set incremented duty
    }
    else
      if (PINC.B1) {                            			// Detect if PORTC pin 1 is pressed
        Delay_ms(40);                           			// Small delay to avoid deboucing effect
        current_duty--;                         			// Decrement duty ratio
        PWM16bit_Change_Duty(current_duty, _TIMER1_CH_A);     		// Set decremented duty ratio
      }
      else
        if (PINC.B2) {                          			// Detect if PORTC pin 2 is pressed
          Delay_ms(40);                         			// Small delay to avoid deboucing effect
          current_duty1++;                      			// Increment duty ratio
          PWM16bit_Change_Duty(current_duty1, _TIMER1_CH_B);  		// Set incremented duty
        }
        else
          if (PINC.B3) {                        			// Detect if PORTC pin 3 is pressed
            Delay_ms(40);                       			// Small delay to avoid deboucing effect
            current_duty1--;                    			// Decrement duty ratio
            PWM16bit_Change_Duty(current_duty1, _TIMER1_CH_B);		// Set decremented duty ratio
          }

  } while(1);                       // Endless loop
     
  }

HW Connection

PWM demonstration

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