Generates pwm outputs on the gpio pins using the dma engine. More...

#include <stdint.h>
#include <string.h>
#include <unistd.h>
#include <memoryManagement/cacheCoherentMemoryProvider.h>
#include <peripherals/dma.h>
#include <peripherals/pwm.h>
#include <peripherals/clockManager.h>
#include <peripherals/gpio.h>
#include <CCRCodingUtils/include/errorManagement.h>
#include <memoryManagement/addressing.h>
#include <CCRCodingUtils/include/utils.h>
#include <utils/pwmByDma.h>
#include "../peripherals/gpio_internal.h"
#include "../peripherals/pwm_internal.h"

Data Structures
struct	channelSetup_struct
	Describes the setup of a channel. More...

Typedefs
typedef struct channelSetup_struct	ChannelSetup
	Describes the setup of a channel.

Functions
int	pwmDma_init (unsigned int pulseDuration_us)
	Initialize: call this before any other function in this file. This sets up the pwm to use it as a timer, so don't mess with it after calling this function. More...

int	pwmDma_isInit ()
	Tells if pwmByDma has been initialized successfully.

unsigned int	pwmDma_get_pulseDuration_us ()
	Returns the duration in microseconds of a single pulse, you can set this duration in pwmDma_init(...) More...

int	pwmDma_isChannelInitialized (int channel)
	Tells if a channel is initialized. More...

int	pwmDma_getChannelPeriodUs (int channel)
	Return the duration in microseconds of a cycle for the specified channel. More...

int	pwmDma_initChannel_periodInPulses (int channel, unsigned int pulsesPerPeriod)
	Sets up the channel to output pwm, you can use only a channel at a time. More...

int	pwmDma_initChannel (int channel, unsigned int period_us)
	Sets up the channel to output pwm. More...

int	pwmDma_freeChannel (int channel)
	Frees a channel initialized with pwmDma_initChannel or pwmDma_initChannel_periodInPulses. More...

int	pwmDma_startChannel (int channel)
	Starts a stopped channel. More...

int	pwmDma_stopChannelWaitCycleEnd (int channel)
	Stops channel waiting for the current cycle to finish. More...

int	pwmDma_stopChannel (int channel)
	Stops channel. More...

int	pwmDma_addPulse (int channel, int bcmPort, unsigned int start_us, unsigned int length_us)
	Sets a pulse on the specified channel and gpio. More...

int	pwmDma_clearPort (int channel, int bcmPort)
	Removes any pulse on this port at the specified channel. More...

int	pwmDma_printWords (int channel)
	For debugging purposes: prints all the set/clear words. More...

int	pwmDma_printControlBlocks (int channel)
	For debugging purposes: prints all the control blocks. More...

int	pwmDma_setMSRatio (int channel, int bcmPort, double ratio)
	Set the port to output a square wave with the specified duty cycle. Will be high for the first ratio*period microseconds and then low. More...

int	pwmDma_addMultiplePulse (int channel, int bcmPort, unsigned int start_us, unsigned int length_us, unsigned int subPeriod_us)
	Adds multiple pulses to the channel at the specified port. The pulse will be repeated every subPeriod_us microseconds. In this way you can simulate a channel initialized with period=subPeriod_us. More...

Detailed Description

Generates pwm outputs on the gpio pins using the dma engine.

It works by writing periodically to the gpio set and clear registers. Precise timing is achieved using the DREQ signal from the pwm: the dma on each cycle writes to the pwm fifo an so is blocked until the pwm consumes the data. So on each cycle:

DMA writes to the gpio set register
DMA writes to the gpio clear register
DMA writes to the pwm FIFO input register When the pwm consumes the data it raises DREQ and the next dma cycle starts

To do so we have to allocate:

A chain of DMA control blocks
One word to write to the gpio set register for each control block
One word to write to the gpio clear register for each control block To the pwm FIFO we can write anything, for example the gpio set word.

If you haven't already, see pwmByDma.h

Function Documentation

int pwmDma_addMultiplePulse	(	int	channel,
		int	bcmPort,
		unsigned int	start_us,
		unsigned int	length_us,
		unsigned int	subPeriod_us
	)

Adds multiple pulses to the channel at the specified port. The pulse will be repeated every subPeriod_us microseconds. In this way you can simulate a channel initialized with period=subPeriod_us.

Parameters

channel	The channel number
bcmPort	The port broadcom number, only ports 0-31 are available
start_us	The start time of the pulse in microseconds, has to be a multiple of the pulse duration, and between 0 and the subPeriod_us
length_us	The length of the pulse in microseconds, has to be a multiple of the pulse duration and not bigger than subPeriod_us
subPeriod_us	The period at which the pulse will be repeated. Has to be a divisor of the period of the channel

int pwmDma_addPulse	(	int	channel,
		int	bcmPort,
		unsigned int	start_us,
		unsigned int	length_us
	)

Sets a pulse on the specified channel and gpio.

Parameters

channel	The channel number
bcmPort	The port broadcom number, only ports 0-31 are available
start_us	The start time of the pulse in microseconds, has to be a multiple of the pulse duration, and between 0 and the period duration of this channel
length_us	The length of the pulse in microseconds, has to be a multiple of the pulse duration

Returns: negative in case of error

int pwmDma_clearPort	(	int	channel,
		int	bcmPort
	)

Removes any pulse on this port at the specified channel.

Parameters

channel	The channel
bcmPort	The port

Returns: negative in case of error

int pwmDma_freeChannel ( int channel )

Frees a channel initialized with pwmDma_initChannel or pwmDma_initChannel_periodInPulses.

Parameters

channel The channel number

Returns: negative in case of error

unsigned int pwmDma_get_pulseDuration_us ( )

Returns the duration in microseconds of a single pulse, you can set this duration in pwmDma_init(...)

Returns: The duration, zero if pwmDma_init hasn't been called

int pwmDma_getChannelPeriodUs ( int channel )

Return the duration in microseconds of a cycle for the specified channel.

Parameters

channel The channel number

Returns: the duration, 0 in case of error

int pwmDma_init ( unsigned int pulseDuration_us )

Initialize: call this before any other function in this file. This sets up the pwm to use it as a timer, so don't mess with it after calling this function.

Parameters

pulseDuration_us The duration of a single pulse in microseconds, in other words: the granularity, the precision. All prime numbers over 4095 and all the numbers over 33546 aren't acceptable.

int pwmDma_initChannel	(	int	channel,
		unsigned int	period_us
	)

Sets up the channel to output pwm.

Parameters

channel	The channel to use
period_us	Duration of a cycle in microseconds

Returns: negative in case of error

int pwmDma_initChannel_periodInPulses	(	int	channel,
		unsigned int	pulsesPerPeriod
	)

Sets up the channel to output pwm, you can use only a channel at a time.

Parameters

channel	The channel to use
pulsesPerPeriod	Number of pulses in a cycle. The resulting period duration is: period_us = pulsesPerPeriod*pulseDuration_us. Where pulseDuration_us is specified in pwmDma_init(...)

Returns: negative in case of error

int pwmDma_isChannelInitialized ( int channel )

Tells if a channel is initialized.

Parameters

channel The channel number

Returns: If the channel has been initialized, 0 in case of error

int pwmDma_printControlBlocks ( int channel )

For debugging purposes: prints all the control blocks.

Returns: negative in case of error

int pwmDma_printWords ( int channel )

For debugging purposes: prints all the set/clear words.

Returns: negative in case of error

int pwmDma_setMSRatio	(	int	channel,
		int	bcmPort,
		double	ratio
	)

Set the port to output a square wave with the specified duty cycle. Will be high for the first ratio*period microseconds and then low.

Parameters

channel	The channel to use
bcmPort	The port to use
ratio	The duty cycle ratio

Returns: negative in case of error

int pwmDma_startChannel ( int channel )

Starts a stopped channel.

Parameters

channel The channel number

Returns: negative in case of error

int pwmDma_stopChannel ( int channel )

Stops channel.

Parameters

channel The channel number

Returns: negative in case of error

int pwmDma_stopChannelWaitCycleEnd ( int channel )

Stops channel waiting for the current cycle to finish.

Parameters

channel The channel number

Returns: negative in case of error

Data Structures

Typedefs

Functions

Detailed Description

Function Documentation