PWM Class Reference

#include <PWM.h>

Inheritance diagram for PWM:

Public Types
enum	PeriodMultiplier { kPeriodMultiplier_1X = 1, kPeriodMultiplier_2X = 2, kPeriodMultiplier_4X = 4 }

Public Member Functions
	PWM (uint32_t channel)
	PWM (uint8_t moduleNumber, uint32_t channel)
virtual	~PWM ()
virtual void	SetRaw (uint8_t value)
virtual uint8_t	GetRaw ()
void	SetPeriodMultiplier (PeriodMultiplier mult)
void	EnableDeadbandElimination (bool eliminateDeadband)
void	SetBounds (int32_t max, int32_t deadbandMax, int32_t center, int32_t deadbandMin, int32_t min)
void	SetBounds (double max, double deadbandMax, double center, double deadbandMin, double min)
uint32_t	GetChannel ()
uint32_t	GetModuleNumber ()
Public Member Functions inherited from SensorBase
	SensorBase ()
virtual	~SensorBase ()
Public Member Functions inherited from ErrorBase
virtual Error &	GetError ()
	Retrieve the current error. Get the current error information associated with this sensor.
virtual const Error &	GetError () const
virtual void	SetErrnoError (const char *contextMessage, const char *filename, const char *function, uint32_t lineNumber) const
	Set error information associated with a C library call that set an error to the "errno" global variable. More...
virtual void	SetImaqError (int success, const char *contextMessage, const char *filename, const char *function, uint32_t lineNumber) const
	Set the current error information associated from the nivision Imaq API. More...
virtual void	SetError (Error::Code code, const char *contextMessage, const char *filename, const char *function, uint32_t lineNumber) const
	Set the current error information associated with this sensor. More...
virtual void	SetWPIError (const char *errorMessage, const char *contextMessage, const char *filename, const char *function, uint32_t lineNumber) const
	Set the current error information associated with this sensor. More...
virtual void	CloneError (ErrorBase *rhs) const
virtual void	ClearError () const
	Clear the current error information associated with this sensor.
virtual bool	StatusIsFatal () const
	Check if the current error code represents a fatal error. More...

Protected Member Functions
virtual void	SetPosition (float pos)
virtual float	GetPosition ()
virtual void	SetSpeed (float speed)
virtual float	GetSpeed ()
void	ValueChanged (ITable *source, const std::string &key, EntryValue value, bool isNew)
void	UpdateTable ()
void	StartLiveWindowMode ()
void	StopLiveWindowMode ()
std::string	GetSmartDashboardType ()
void	InitTable (ITable *subTable)
ITable *	GetTable ()
Protected Member Functions inherited from SensorBase
void	AddToSingletonList ()
Protected Member Functions inherited from ErrorBase
	ErrorBase ()
	Initialize the instance status to 0 for now.

Protected Attributes
bool	m_eliminateDeadband
int32_t	m_maxPwm
int32_t	m_deadbandMaxPwm
int32_t	m_centerPwm
int32_t	m_deadbandMinPwm
int32_t	m_minPwm
ITable *	m_table
Protected Attributes inherited from ErrorBase
Error	m_error

Static Protected Attributes
static constexpr float	kDefaultPwmPeriod = 5.05
static constexpr float	kDefaultPwmCenter = 1.5
static const int32_t	kDefaultPwmStepsDown = 128
static const int32_t	kPwmDisabled = 0
Static Protected Attributes inherited from ErrorBase
static SEM_ID	_globalErrorMutex = semMCreate(SEM_Q_PRIORITY | SEM_DELETE_SAFE | SEM_INVERSION_SAFE)
static Error	_globalError

Friends
class	DigitalModule

Additional Inherited Members
Static Public Member Functions inherited from SensorBase
static void	DeleteSingletons ()
static uint32_t	GetDefaultAnalogModule ()
static uint32_t	GetDefaultDigitalModule ()
static uint32_t	GetDefaultSolenoidModule ()
static bool	CheckAnalogModule (uint8_t moduleNumber)
static bool	CheckDigitalModule (uint8_t moduleNumber)
static bool	CheckPWMModule (uint8_t moduleNumber)
static bool	CheckRelayModule (uint8_t moduleNumber)
static bool	CheckSolenoidModule (uint8_t moduleNumber)
static bool	CheckDigitalChannel (uint32_t channel)
static bool	CheckRelayChannel (uint32_t channel)
static bool	CheckPWMChannel (uint32_t channel)
static bool	CheckAnalogChannel (uint32_t channel)
static bool	CheckSolenoidChannel (uint32_t channel)
Static Public Member Functions inherited from ErrorBase
static void	SetGlobalError (Error::Code code, const char *contextMessage, const char *filename, const char *function, uint32_t lineNumber)
static void	SetGlobalWPIError (const char *errorMessage, const char *contextMessage, const char *filename, const char *function, uint32_t lineNumber)
static Error &	GetGlobalError ()
Static Public Attributes inherited from SensorBase
static const uint32_t	kSystemClockTicksPerMicrosecond = 40
static const uint32_t	kDigitalChannels = 14
static const uint32_t	kAnalogChannels = 8
static const uint32_t	kAnalogModules = 2
static const uint32_t	kDigitalModules = 2
static const uint32_t	kSolenoidChannels = 8
static const uint32_t	kSolenoidModules = 2
static const uint32_t	kPwmChannels = 10
static const uint32_t	kRelayChannels = 8
static const uint32_t	kChassisSlots = 8

Detailed Description

Class implements the PWM generation in the FPGA.

The values supplied as arguments for PWM outputs range from -1.0 to 1.0. They are mapped to the hardware dependent values, in this case 0-255 for the FPGA. Changes are immediately sent to the FPGA, and the update occurs at the next FPGA cycle. There is no delay.

As of revision 0.1.10 of the FPGA, the FPGA interprets the 0-255 values as follows:

• 255 = full "forward"
• 254 to 129 = linear scaling from "full forward" to "center"
• 128 = center value
• 127 to 2 = linear scaling from "center" to "full reverse"
• 1 = full "reverse"
• 0 = disabled (i.e. PWM output is held low)

Constructor & Destructor Documentation

PWM::PWM ( uint32_t  channel )

explicit

Allocate a PWM in the default module given a channel.

Using a default module allocate a PWM given the channel number. The default module is the first slot numerically in the cRIO chassis.

Parameters

channel

The PWM channel on the digital module.

PWM::PWM	(	uint8_t	moduleNumber,
		uint32_t	channel
	)

Allocate a PWM given a module and channel. Allocate a PWM using a module and channel number.

Parameters

moduleNumber	The digital module (1 or 2).
channel	The PWM channel on the digital module (1..10).

PWM::~PWM ( )

virtual

Free the PWM channel.

Free the resource associated with the PWM channel and set the value to 0.

Member Function Documentation

void PWM::EnableDeadbandElimination

(

bool

eliminateDeadband

)

Optionally eliminate the deadband from a speed controller.

Parameters

eliminateDeadband

If true, set the motor curve on the Jaguar to eliminate the deadband in the middle of the range. Otherwise, keep the full range without modifying any values.

float PWM::GetPosition ( )

protectedvirtual

Get the PWM value in terms of a position.

This is intended to be used by servos.

Precondition

SetMaxPositivePwm() called.

SetMinNegativePwm() called.

Returns

The position the servo is set to between 0.0 and 1.0.

uint8_t PWM::GetRaw ( )

virtual

Get the PWM value directly from the hardware.

Read a raw value from a PWM channel.

Returns

Raw PWM control value. Range: 0 - 255.

float PWM::GetSpeed ( )

protectedvirtual

Get the PWM value in terms of speed.

This is intended to be used by speed controllers.

Precondition

SetMaxPositivePwm() called.

SetMinPositivePwm() called.

SetMaxNegativePwm() called.

SetMinNegativePwm() called.

Returns

The most recently set speed between -1.0 and 1.0.

void PWM::SetBounds	(	int32_t	max,
		int32_t	deadbandMax,
		int32_t	center,
		int32_t	deadbandMin,
		int32_t	min
	)

Set the bounds on the PWM values. This sets the bounds on the PWM values for a particular each type of controller. The values determine the upper and lower speeds as well as the deadband bracket.

Parameters

max	The Minimum pwm value
deadbandMax	The high end of the deadband range
center	The center speed (off)
deadbandMin	The low end of the deadband range
min	The minimum pwm value

void PWM::SetBounds	(	double	max,
		double	deadbandMax,
		double	center,
		double	deadbandMin,
		double	min
	)

Set the bounds on the PWM pulse widths. This sets the bounds on the PWM values for a particular type of controller. The values determine the upper and lower speeds as well as the deadband bracket.

Parameters

max	The max PWM pulse width in ms
deadbandMax	The high end of the deadband range pulse width in ms
center	The center (off) pulse width in ms
deadbandMin	The low end of the deadband pulse width in ms
min	The minimum pulse width in ms

void PWM::SetPeriodMultiplier

(

PeriodMultiplier

mult

)

Slow down the PWM signal for old devices.

Parameters

mult	The period multiplier to apply to this channel

void PWM::SetPosition ( float  pos )

protectedvirtual

Set the PWM value based on a position.

This is intended to be used by servos.

Precondition

SetMaxPositivePwm() called.

SetMinNegativePwm() called.

Parameters

pos	The position to set the servo between 0.0 and 1.0.

void PWM::SetRaw ( uint8_t  value )

virtual

Set the PWM value directly to the hardware.

Write a raw value to a PWM channel.

Parameters

value

Raw PWM value. Range 0 - 255.

void PWM::SetSpeed ( float  speed )

protectedvirtual

Set the PWM value based on a speed.

This is intended to be used by speed controllers.

Precondition

SetMaxPositivePwm() called.

SetMinPositivePwm() called.

SetCenterPwm() called.

SetMaxNegativePwm() called.

SetMinNegativePwm() called.

Parameters

speed

The speed to set the speed controller between -1.0 and 1.0.

Reimplemented in SafePWM.

Member Data Documentation

constexpr float PWM::kDefaultPwmCenter = 1.5

staticprotected

kDefaultPwmCenter is the PWM range center in ms

constexpr float PWM::kDefaultPwmPeriod = 5.05

staticprotected

kDefaultPwmPeriod is in ms

• 20ms periods (50 Hz) are the "safest" setting in that this works for all devices
• 20ms periods seem to be desirable for Vex Motors
• 20ms periods are the specified period for HS-322HD servos, but work reliably down to 10.0 ms; starting at about 8.5ms, the servo sometimes hums and get hot; by 5.0ms the hum is nearly continuous
• 10ms periods work well for Victor 884
• 5ms periods allows higher update rates for Luminary Micro Jaguar speed controllers. Due to the shipping firmware on the Jaguar, we can't run the update period less than 5.05 ms.

kDefaultPwmPeriod is the 1x period (5.05 ms). In hardware, the period scaling is implemented as an output squelch to get longer periods for old devices.

const int32_t PWM::kDefaultPwmStepsDown = 128

staticprotected

kDefaultPWMStepsDown is the number of PWM steps below the centerpoint

---

The documentation for this class was generated from the following files:

• PWM.h
• PWM.cpp