PIC18 PWM Driver

The driver provides PWM output functionality for the PIC18F26K83 using the CCP (Capture/Compare/PWM) modules. It supports up to four PWM channels, each with configurable pin mapping. Timer 2 is utilized by this driver to manage PWM periods.

Integration

Pin Configuration

CONCAT(a, b, c)

Concatenates three tokens to dynamically form register names.

Parameters:

a – First part of the token.
b – Second part of the token.
c – Third part of the token.

CCPR_L(module)

Accesses the CCPR Low register for the specified module.

Parameters:

module – CCP module number (1-4).

CCPR_H(module)

Accesses the CCPR High register for the specified module.

Parameters:

module – CCP module number (1-4).

CCP_CON(module)

Accesses the CCPxCON control register for the specified module.

Parameters:

module – CCP module number (1-4).

GET_TRIS_REG(port)

Retrieves the TRIS register for the specified port.

Parameters:

port – Port letter (A, B, C).

GET_PPS_REG(port, pin)

Retrieves the PPS register address for the specified port and pin.

Parameters:

port – Port letter (A, B, C).
pin – Pin number (0-7).

SET_TRIS_OUTPUT(port, pin)

Sets the specified pin as output by modifying the TRIS register.

Parameters:

port – Port letter (A, B, C).
pin – Pin number (0-7).

ASSIGN_PPS(port, pin, ccp_module)

Assigns the CCP module to the specified PPS register to map the peripheral to the desired pin.

Parameters:

port – Port letter (A, B, C).
pin – Pin number (0-7).
ccp_module – CCP module number (1-4).

CCP Mode Configuration

CONFIGURE_CCP_MODE(ccp_module, ccp_con)

Configure the CCP module for PWM mode.

Parameters:

ccp_module – CCP module number (1-4)
ccp_con – CCPxCON register to configure

Output Pin Configuration

SET_PWM_OUTPUT_PIN(ccp_module, output_pin)

Set the TRIS register for the output pin.

Parameters:

ccp_module – CCP module number (1-4)
output_pin – Output pin number

Duty Cycle Configuration

WRITE_DUTY_CYCLE(ccp_module, duty_cycle)

Write the 10-bit duty cycle value to the appropriate CCPRxH:CCPRxL register pair.

Parameters:

ccp_module – CCP module number (1-4)
duty_cycle – 10-bit duty cycle value (0-1023)

PWM Controller Functions

PWM Pin Configuration Structure

type pwm_pin_config_t

Structure that holds the configuration details for a PWM pin.

Param port:: Port letter (A, B, C).
Param pin:: Pin number (0-7).
Param pps_reg:: PPS register value for this pin.

Initialization

w_status_t pwm_init(uint8_t ccp_module, pwm_pin_config_t pin_config, uint16_t pwm_period)

Initializes PWM for the specified CCP module with the given pin configuration and PWM period.

Parameters:

ccp_module – CCP module number (1-4).
pin_config – PWM pin configuration structure containing port, pin, and PPS register values.
pwm_period – PWM period value.

Returns:

W_SUCCESS on successful initialization, otherwise an error code.

This function configures Timer 2, sets the PWM period, and enables the PWM output for the specified CCP module.

PWM Operation

w_status_t pwm_update_duty_cycle(uint8_t ccp_module, uint16_t duty_cycle)

Updates the duty cycle of the specified CCP module to the new value.

Parameters:

ccp_module – CCP module number (1-4).
duty_cycle – New duty cycle value (0-1023).

Returns:

W_SUCCESS if successful, W_INVALID_PARAM if parameters are out of range.

The duty cycle is a 10-bit value that determines the percentage of time the signal stays high. The lower 8 bits are written to CCPRxL, and the upper 2 bits are written to CCPRxH.

Timer Configuration

CONFIGURE_TIMER2(pwm_period)

Configures Timer 2 to manage PWM periods. The prescaler and postscaler are set to 1:1.

Parameters:

pwm_period – PWM period value to load into the PR2 register.

Helper Functions

PPS Configuration

static w_status_t configure_pps(uint8_t ccp_module, pwm_pin_config_t pin_config)

Configures Peripheral Pin Select (PPS) for the specified pin and CCP module. This function is essential for routing the PWM signal to the correct output pin.

Parameters:

ccp_module – CCP module number (1-4).
pin_config – Structure containing port, pin, and PPS register values.

Returns:

W_SUCCESS if successful, W_INVALID_PARAM if the module number is out of range.

Error Handling

Error Codes

W_SUCCESS: Operation completed successfully.
W_INVALID_PARAM: Parameter value is out of range. Typically returned if an invalid CCP module number or duty cycle value is provided.

Practical Considerations

Timer Usage: Ensure Timer 2 is not shared with other peripherals to avoid conflicts in PWM generation.
Prescaler and Postscaler: The prescaler and postscaler are currently set to 1:1 for simplicity. These can be adjusted to modify the frequency of the PWM signal.
Pin Mapping: Correct pin mapping is critical for proper operation. Incorrect configuration can result in no output or conflicts with other peripherals.