CC2538 PWM driver

Files
file	pwm.c
	Driver for the CC2538 PWM.
file	pwm.h
	Header file for the CC2538 PWM driver.

PWM functions
int8_t	pwm_enable (uint32_t freq, uint8_t duty, uint32_t count, uint8_t timer, uint8_t ab)
	Configures the general purpose timer in PWM mode.
int8_t	pwm_stop (uint8_t timer, uint8_t ab, uint8_t port, uint8_t pin, uint8_t state)
	Halts the PWM in a given GPT/timer.
int8_t	pwm_start (uint8_t timer, uint8_t ab, uint8_t port, uint8_t pin)
	Once configured, starts the PWM.
int8_t	pwm_set_direction (uint8_t timer, uint8_t ab, uint8_t dir)
	Sets the PWM duty cycle signal direction (high/low)
int8_t	pwm_toggle_direction (uint8_t timer, uint8_t ab)
	Toggle the PWM signal direction (inverts the current duty cycle)
int8_t	pwm_disable (uint8_t timer, uint8_t ab, uint8_t port, uint8_t pin)
	Disables a previously PWM configured GPTn.

Detailed Description

Driver for the CC2538 PWM on GPTIMER

The driver uses the timers A and B of the general purpose timers to create a PWM signal, allowing to set a duty cycle value from 1-100%. This implementation relies on having a peripheral clock of 16MHz, but it can be easily changed (see PWM_FREQ_MIN and PWM_FREQ_MAX values). The reason it is fixed to these frequencies is to have a consistent duty cycle implementation.

Depending on the specific needs these limits can be changed to meet a given duty cycle and lower frequencies by using the prescaler (GPTIMER_TnPR).

Running a PWM timer prevents the LPM driver from dropping to PM1+.

Function Documentation

pwm_disable()

int8_t pwm_disable	(	uint8_t	timer,
		uint8_t	ab,
		uint8_t	port,
		uint8_t	pin )

Disables a previously PWM configured GPTn.

Parameters

timer	General purpose timer to disable [0-3]
ab	Select which timer to disable (Timer A or B)
port	Port number used as PWM to disable (set as input GPIO)
pin	Pin number used as PWM to disable (set as input GPIO)

Returns

PWM_SUCCESS if successful, else PWM_ERROR

This function disables a specific timer (A or B) and reset related registers to default values. The user must explicitely pass the port/pin number of the pin to disable as PWM and to be configured as input GPIO. The module clock is not disabled with this function

Definition at line 330 of file pwm.c.

References GPIO_D_NUM, GPIO_PIN_MASK, GPIO_PORT_TO_BASE, GPIO_SET_INPUT, GPIO_SOFTWARE_CONTROL, GPTIMER_TAILR, GPTIMER_TAMATCHR, GPTIMER_TAMR, IOC_OVERRIDE_DIS, ioc_set_over(), and pwm_stop().

Referenced by servo_stop().

pwm_enable()

int8_t pwm_enable	(	uint32_t	freq,
		uint8_t	duty,
		uint32_t	count,
		uint8_t	timer,
		uint8_t	ab )

Configures the general purpose timer in PWM mode.

Parameters

freq	PWM frequency (in Hz)
duty	PWM duty cycle (percentage in integers)
count	PWM duty cycle (count number)
timer	General purpose timer to use [0-3]
ab	Select which timer to use (Timer A or B)

Returns

PWM_SUCCESS if successful, else PWM_ERROR

Definition at line 93 of file pwm.c.

References count, GPTIMER_CFG, GPTIMER_CTL, GPTIMER_CTL_TAEN, GPTIMER_CTL_TAPWML, GPTIMER_CTL_TBEN, GPTIMER_CTL_TBPWML, GPTIMER_TAILR, GPTIMER_TAMATCHR, GPTIMER_TAMR, GPTIMER_TAMR_TAAMS, GPTIMER_TAPMR, GPTIMER_TAPR, SYS_CTRL_DCGCGPT, SYS_CTRL_DCGCGPT_GPT0, sys_ctrl_get_sys_clock(), SYS_CTRL_RCGCGPT, SYS_CTRL_RCGCGPT_GPT0, SYS_CTRL_SCGCGPT, and SYS_CTRL_SCGCGPT_GPT0.

Referenced by servo_position().

pwm_set_direction()

int8_t pwm_set_direction	(	uint8_t	timer,
		uint8_t	ab,
		uint8_t	dir )

Sets the PWM duty cycle signal direction (high/low)

Parameters

timer	General purpose timer [0-3]
ab	Select which timer to use (Timer A or B)
dir	Direction of the PWM signal, PWM_SIGNAL_INVERTED or PWM_SIGNAL_STRAIGHT

Returns

PWM_SUCCESS if successful, else PWM_ERROR

Definition at line 274 of file pwm.c.

References GPTIMER_CTL, GPTIMER_CTL_TAPWML, and GPTIMER_CTL_TBPWML.

pwm_start()

int8_t pwm_start	(	uint8_t	timer,
		uint8_t	ab,
		uint8_t	port,
		uint8_t	pin )

Once configured, starts the PWM.

Parameters

timer	General purpose timer to start [0-3]
ab	Select which timer to start (Timer A or B)
port	Port number to use as PWM
pin	Pin number to use as PWM

Returns

PWM_SUCCESS if successful, else PWM_ERROR

Definition at line 235 of file pwm.c.

References GPIO_D_NUM, GPIO_PERIPHERAL_CONTROL, GPIO_PIN_MASK, GPIO_PORT_TO_BASE, GPTIMER_CTL, GPTIMER_CTL_TAEN, GPTIMER_CTL_TBEN, IOC_OVERRIDE_OE, ioc_set_over(), and ioc_set_sel().

Referenced by servo_position().

pwm_stop()

int8_t pwm_stop	(	uint8_t	timer,
		uint8_t	ab,
		uint8_t	port,
		uint8_t	pin,
		uint8_t	state )

Halts the PWM in a given GPT/timer.

Parameters

timer	General purpose timer to stop [0-3]
ab	Select which timer to stop (Timer A or B)
port	Port of the gpio port mapped to the PWM to stop
pin	Pin of the gpio port mapped to the PWM to stop
state	State to leave the pin once stopped, on (1) or off (0)

Returns

PWM_SUCCESS if successful, else PWM_ERROR

Definition at line 190 of file pwm.c.

References GPIO_CLR_PIN, GPIO_D_NUM, GPIO_PIN_MASK, GPIO_PORT_TO_BASE, GPIO_SET_OUTPUT, GPIO_SET_PIN, GPIO_SOFTWARE_CONTROL, GPTIMER_CTL, GPTIMER_CTL_TAEN, GPTIMER_CTL_TBEN, IOC_OVERRIDE_DIS, and ioc_set_over().

Referenced by pwm_disable().

pwm_toggle_direction()

int8_t pwm_toggle_direction	(	uint8_t	timer,
		uint8_t	ab )

Toggle the PWM signal direction (inverts the current duty cycle)

Parameters

timer	General purpose timer to use [0-3]
ab	Select which timer to use (Timer A or B)

Returns

PWM_SUCCESS if successful, else PWM_ERROR

Definition at line 302 of file pwm.c.

References GPTIMER_CTL, GPTIMER_CTL_TAPWML, and GPTIMER_CTL_TBPWML.