PWMTimerMSP432.h File Reference

Detailed Description

PWM driver implementation using Timer_A peripherals.

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The PWM header file should be included in an application as follows:

#include <ti/drivers/PWM.h>
#include <ti/drivers/pwm/PWMTimerMSP432.h>

• Refer to PWM.h for a complete description of APIs & example of use.

Operation

This driver configures an MSP432 Timer_A peripheral for PWM. If the timer is already in use (by the kernel for instance), PWM instances will not be opened.

When used for PWM generation, each Timer_A can produce up to 6 PWM outputs and this driver manages each output as an independent PWM instance. However since a single period and prescalar are used for all Timer outputs, there are limitations in place to ensure proper operation:

• The PWM period and prescalar are calculated and set based on the first instance opened. Opening a second instance will fail if the period is not the same as what was set by the first instance.

The timer is automatically configured in count-up mode using the clock source specified in the hwAttrs structure. In PWM mode, the timer capture/compare register 0 is used as the period register and cannot be used to generate a PWM output.

The period and duty registers are 16 bits wide, thus a prescalar is used to divide the input clock and allow for larger periods. The maximum period supported is calculated as:

• MAX_PERIOD = (MAX_PRESCALAR * MAX_MATCH_VALUE) / CYCLES_PER_US
• Ex:
  • 12 MHz clock: (64 * 65535) / 12 = 349520 microseconds
  • 6 MHz clock: (64 * 65535) / 6 = 699040 microseconds
  • 3 MHz clock: (64 * 65535) / 3 = 1398080 microseconds

After opening, the PWM_setPeriod() API can be used to change the PWM period. Keep in mind the period is shared by all other PWMs on the timer, so all other PWM outputs on the timer will change. Additionally, a call to PWM_setPeriod() will fail if the new period requires a prescalar different than the one set when initially configured.

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#include <stdbool.h>
#include <ti/drivers/PWM.h>

Include dependency graph for PWMTimerMSP432.h:

Go to the source code of this file.

Data Structures
struct	PWMTimerMSP432_HWAttrsV1
	PWMTimerMSP432 Hardware attributes. More...
struct	PWMTimerMSP432_Status
	PWMTimerMSP432_Status. More...
struct	PWMTimerMSP432_Object
	PWMTimerMSP432 Object. More...

Macros
#define	PWMTimerMSP432_NUM_TIMERS   (4)
#define	PWMTimerMSP432_NUM_PWM_OUTPUTS   (6)

Typedefs
typedef struct PWMTimerMSP432_HWAttrsV1	PWMTimerMSP432_HWAttrsV1
	PWMTimerMSP432 Hardware attributes. More...
typedef struct PWMTimerMSP432_Status	PWMTimerMSP432_Status
	PWMTimerMSP432_Status. More...
typedef struct PWMTimerMSP432_Object	PWMTimerMSP432_Object
	PWMTimerMSP432 Object. More...

Variables
const PWM_FxnTable	PWMTimerMSP432_fxnTable

Macro Definition Documentation

#define PWMTimerMSP432_NUM_TIMERS   (4)

#define PWMTimerMSP432_NUM_PWM_OUTPUTS   (6)

Typedef Documentation

typedef struct PWMTimerMSP432_HWAttrsV1 PWMTimerMSP432_HWAttrsV1

PWMTimerMSP432 Hardware attributes.

These fields are used by driverlib APIs and therefore must be populated by driverlib macro definitions. For msp432_driverlib these definitions are found in:

• msp432p401r.h
• gpio.h
• timer_a.h

A sample structure is shown below:

const PWMTimerMSP432_HWAttrs PWMTimerMSP432HWAttrs[] = {
    {
        .timerBaseAddr = TIMER_A1_BASE,
        .clockSource = TIMER_A_CLOCKSOURCE_SMCLK,
        .compareRegister = TIMER_A_CAPTURECOMPARE_REGISTER_1,
        .gpioPort = GPIO_PORT_P2,
        .gpioPinIndex = GPIO_PIN1,
        .pwmMode = GPIO_PRIMARY_MODULE_FUNCTION
    },
};

typedef struct PWMTimerMSP432_Status PWMTimerMSP432_Status

PWMTimerMSP432_Status.

The application must not access any member variables of this structure!

typedef struct PWMTimerMSP432_Object PWMTimerMSP432_Object

PWMTimerMSP432 Object.

The application must not access any member variables of this structure!

Variable Documentation

const PWM_FxnTable PWMTimerMSP432_fxnTable