4.20.3 16-bit PWM with Compare Mode

• Add PWMx Component to the project

• Configure:

  1. PWMx_16BIT component as described in the example.

  2. Any other components or pins needed for the use case.

• Generate the code

• Add the code snippet(s) to the application code

• Program the board

1. Add PWMx_16BIT  

• Hardware Settings:

  1. Clock Source: LFINTOSC.

• Slice 1 Output Settings

  1. Requested Frequency (kHz): 1 (Default).

  2. Output 1 Duty Cycle (%): 25.

• Pin Grid View:

  1. Select a pin for PWM1OUT1 (this is the PWM output pin)

• Pins:

  1. PWM1OUT1 output pin: Uncheck Analog, name it PWM.

• Connect PWM to DebugIO PIN (check schematics) using a wire, to see PWM waveform on the MPLAB Data Visualizer

#include "mcc_generated_files/system/system.h"  

int main(void)
{
    SYSTEM_Initialize();

    while(1){}
}

1. Add PWMx_16BIT

2. Add TimerX

• Software Settings

  1. Custom Name: PWM (so the user can easily switch between PWM instances)

• Slice 1 Output Settings

  1. Requested Frequency (kHz): 1 (default)

  2. Invert Output1 Polarity: Yes (If LED is active low: Check schematics)

• Hardware Settings

  1. Timer Mode: 16-bit

  2. Clock Source: LFINTOSC

  3. Requested Period (s): 1(s)  

• Interrupt Settings

  1. TMR Interrupt: Yes. (Timer callback used to change PWM duty cycle)

• Pin Grid View:

  1. Select a pin for PWM1OUT1 (On a LED pin if possible)

• Pins:

  1. PWM1OUT1 output pin: Uncheck Analog, name it PWM.

• Connect PWM to DebugIO PIN (check schematics) using a wire, to see PWM waveform on the MPLAB Data Visualizer

#include "mcc_generated_files/system/system.h"

#define NO_DUTY_CYCLES    (5)

/* Create a pointer of type TMR_INTERFACE and assign it to the address of the Timer0 TMR_INTERFACE struct.
This enables us to access the portable API interface, ensuring it's easy to change the peripheral instance that the timer runs on. */
const struct TMR_INTERFACE *Timer = &Timer0;
static uint8_t currentDutyCyclePos = 1;

/*
 *  Enum that encompasses all the values for PWM's duty cycle register that the application cycles through.
 */
typedef enum DUTY_CYCLE
{
    DUTY_CYCLE_0   = 0x0000,    
    DUTY_CYCLE_2   = 0x0004,  
    DUTY_CYCLE_5   = 0x000A,  
    DUTY_CYCLE_10  = 0x0014,
    DUTY_CYCLE_100 = 0x00C8
} duty_cycle_t;

/*
 *  PWM duty cycles that the application cycle through. LEDs are non linear and saturate quickly, so the duty values are low.
 *  NOTE: If LED is active low: Invert Output1 Polarity: Yes 
 */
static duty_cycle_t const dutyCycles[NO_DUTY_CYCLES] = {
    DUTY_CYCLE_0,
    DUTY_CYCLE_2,
    DUTY_CYCLE_5,
    DUTY_CYCLE_10,
    DUTY_CYCLE_100  //Starts ON fully.
};

/*
 *  Wrapper made for the PWM's API to update the duty cycle.
 */
inline static void UpdateDutyCycle(duty_cycle_t const dutyCycle)
{
    PWM_SetSlice1Output1DutyCycleRegister(dutyCycle);
    PWM_LoadBufferRegisters();
}

void Timer_Callback_SwitchDutyCycle(void){
    
    UpdateDutyCycle(dutyCycles[currentDutyCyclePos]);
    currentDutyCyclePos = (currentDutyCyclePos + 1) % NO_DUTY_CYCLES;
}

int main(void)
{
    SYSTEM_Initialize();
    Timer->TimeoutCallbackRegister(Timer_Callback_SwitchDutyCycle);

    INTERRUPT_GlobalInterruptEnable();

    while(1){}
}

• Add PWM

• Software Settings

  1. Custom Name: PWM (So can easily change PWM hardware instance use case runs on)

• Slice 1 Output Settings

  1. Invert Output1 Polarity: Yes (If LED is active low: Check schematics)  

• Pin Grid View:

  1. Select a pin for PWM1OUT1 (Select a LED pin if possible)

  2. Select the input pin for GPIO for BUTTON (check schematic)

• Pins:

  1. PWM out pin: Custom name "PWM", uncheck Analog

  2. BUTTON pin: Custom name "BUTTON",

  3. Enable Weak Pullup if needed (check schematic)

  4. Interrupt on Change: Sense negative/positive on BUTTON press (check schematic)

1. Connect PWM_OUT to LED using a wire to be able to see the result on the LED (if PWM pin is different from LED pin)

#include "mcc_generated_files/system/system.h"
#define NO_DUTY_CYCLES       (5)

static uint8_t currentDutyCyclePos = 1;
volatile bool CHANGE_DUTYCYCLE = false;

/*
 *  Enum that encompasses all the values for PWM's duty cycle register that the application cycles through.
 */
typedef enum DUTY_CYCLE
{
    DUTY_CYCLE_0   = 0x0000,    
    DUTY_CYCLE_2   = 0x0004,  
    DUTY_CYCLE_5   = 0x000A,  
    DUTY_CYCLE_10  = 0x0014,
    DUTY_CYCLE_100 = 0x00C8
} duty_cycle_t;

/*
 *  PWM duty cycles that the application cycle through. LEDs are non linear and saturate quickly, so the duty values are low.
 *  NOTE: If LED is active low: Invert Output1 Polarity: Yes 
 */
static duty_cycle_t const dutyCycles[NO_DUTY_CYCLES] = {
    DUTY_CYCLE_0,
    DUTY_CYCLE_2,
    DUTY_CYCLE_5,
    DUTY_CYCLE_10,
    DUTY_CYCLE_100  //Starts ON fully.
};

/*
 *  Wrapper made for the PWM's API to update the duty cycle.
 */
inline static void UpdateDutyCycle(duty_cycle_t const dutyCycle)
{
    PWM_SetSlice1Output1DutyCycleRegister(dutyCycle);
    PWM_LoadBufferRegisters();
}

void BUTTON_Callback_SwitchDutyCycle(void)
{
    INTERRUPT_GlobalInterruptDisable();
    UpdateDutyCycle(dutyCycles[currentDutyCyclePos]);
    currentDutyCyclePos = (currentDutyCyclePos + 1) % NO_DUTY_CYCLES;
    CHANGE_DUTYCYCLE = true;    
}

int main(void)
{
    SYSTEM_Initialize();
    RC0_SetInterruptHandler(BUTTON_Callback_SwitchDutyCycle);  //Change RC0 to pin connected to BUTTON
    
    INTERRUPT_GlobalInterruptEnable();

    while(1){
        if(CHANGE_DUTYCYCLE)
        {
            CHANGE_DUTYCYCLE = false;
            __delay_ms(50);  //Debounce
            INTERRUPT_GlobalInterruptEnable();
        }
    }
}

1. Add PWMx_16BIT

2. Add TimerX

• Software Settings

  1. Custom Name: PWM (so the user can easily switch between PWM instances)

• Slice 1 Output Settings

  1. Requested Frequency (kHz): 1 (default)

• Device Resources: Add TIMER from Drivers (Select any timer).

• Hardware Settings:

  1. So that Requested Period (s) ≤ Max Period, modify Clock Prescaler/Postscaler/Clock Source

  2. Requested Period (s): 0.02 (20 ms)

• Interrupt Settings

  1. TMR Interrupt: Yes. (Timer callback used to change PWM duty cycle)

• Pin Grid View:

  1. Select a pin for PWM1OUT1 (On a LED pin if possible)

• Pins:

  1. PWM1OUT1 output pin: Uncheck Analog, name it IO_PWM.

1. Connect PWM_OUT to LED using a wire to be able to see the result on the LED (if PWM pin is different from LED pin)

#include "mcc_generated_files/system/system.h"

static void Timer_Callback_20ms(void);
static void PWM_DutyCycleSetPercentage_Slice1(uint16_t, uint16_t, uint16_t);
static const struct TMR_INTERFACE *Timer = &TimerX; 
// TODO: Replace Timer0 with name of const struct TMR_INTERFACE, from MCC Generated Files > timer > tmrx.c

#define MAXIMUM_INPUT_VALUE 100  // TODO: Replace with the desired maximum value, e.g. a 16 bit ADC connected to a potentiometer could be 4100)
static uint16_t Count = 0;
static uint16_t periodCountTop = 100;

void PWM_DutyCycleSetPercentage_Slice1(uint16_t current, uint16_t max, uint16_t periodCountTop)
{
    uint16_t PWM_DytyCyclePercentage = (1.0f - ((double) current / (double) max)) * periodCountTop;
    PWM_SetSlice1Output1DutyCycleRegister(PWM_DytyCyclePercentage);
    PWM_LoadBufferRegisters();
}

static void Timer_Callback_20ms(void)
{
    /* If used with an analog sensor or a simple POT, this function could be called when ADC result available, replacing Count with adcResult, and updating MAXIMUM_INPUT_VALUE*/ 
    PWM_DutyCycleSetPercentage_Slice1(Count, MAXIMUM_INPUT_VALUE, periodCountTop);
    
    IO_Debug_Toggle();
    if (Count < MAXIMUM_INPUT_VALUE)
    {
        Count = Count++;
    }
    else
    {
        Count = 0;
    }
}

int main(void)
{
    SYSTEM_Initialize();
    Timer->TimeoutCallbackRegister(Timer_Callback_20ms);
    PWM_WritePeriodRegister(periodCountTop); //Set number of counts for PWM period, set here to make code more readable.

    INTERRUPT_GlobalInterruptEnable();

    while (1)
    {
    }
}