ElectRoidWarE: Control LED Light brightness using PWM

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 UART 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).
For better understanding of PWM module it would be best to start with the example provided in Examples folder of our mikroC PRO for AVR compiler.
When you select a MCU, mikroC PRO for AVR automatically loads the correct PWM library (or libraries), 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.
mikroC PRO for AVR does not support enhanced PWM modules.

Library Routines

PWMx_Init
PWMx_Set_Duty
PWMx_Start
PWMx_Stop

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_PHASE_CORRECT_MODE	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

PWM_C0_Init(1000, _PWM_SINGLE_SLOPE);

PWMx_Set_Duty

Prototype	void PWMx_Set_Duty(unsigned short duty);
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.
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

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_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();

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.
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.


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





}