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PWM Class Reference

Class implements the PWM generation in the FPGA. More...

#include <PWM.h>

Inheritance diagram for PWM:
SensorBase ITableListener LiveWindowSendable ErrorBase Sendable SafePWM Jaguar SD540 Servo Spark Talon TalonSRX Victor VictorSP

Public Types

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

Public Member Functions

 PWM (uint32_t channel)
 Allocate a PWM given a channel number. More...
 
virtual ~PWM ()
 Free the PWM channel. More...
 
virtual void SetRaw (unsigned short value)
 Set the PWM value directly to the hardware. More...
 
virtual unsigned short GetRaw () const
 Get the PWM value directly from the hardware. More...
 
void SetPeriodMultiplier (PeriodMultiplier mult)
 Slow down the PWM signal for old devices. More...
 
void SetZeroLatch ()
 
void EnableDeadbandElimination (bool eliminateDeadband)
 Optionally eliminate the deadband from a speed controller. More...
 
void SetBounds (int32_t max, int32_t deadbandMax, int32_t center, int32_t deadbandMin, int32_t min)
 Set the bounds on the PWM values. More...
 
void SetBounds (double max, double deadbandMax, double center, double deadbandMin, double min)
 Set the bounds on the PWM pulse widths. More...
 
uint32_t GetChannel () const
 
- Public Member Functions inherited from SensorBase
 SensorBase ()
 Creates an instance of the sensor base and gets an FPGA handle.
 
 SensorBase (const SensorBase &)=delete
 
SensorBaseoperator= (const SensorBase &)=delete
 
- Public Member Functions inherited from ErrorBase
 ErrorBase (const ErrorBase &)=delete
 
ErrorBaseoperator= (const ErrorBase &)=delete
 
virtual ErrorGetError ()
 Retrieve the current error. More...
 
virtual const ErrorGetError () const
 
virtual void SetErrnoError (llvm::StringRef contextMessage, llvm::StringRef filename, llvm::StringRef 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, llvm::StringRef contextMessage, llvm::StringRef filename, llvm::StringRef function, uint32_t lineNumber) const
 Set the current error information associated from the nivision Imaq API. More...
 
virtual void SetError (Error::Code code, llvm::StringRef contextMessage, llvm::StringRef filename, llvm::StringRef function, uint32_t lineNumber) const
 Set the current error information associated with this sensor. More...
 
virtual void SetWPIError (llvm::StringRef errorMessage, Error::Code code, llvm::StringRef contextMessage, llvm::StringRef filename, llvm::StringRef function, uint32_t lineNumber) const
 Set the current error information associated with this sensor. More...
 
virtual void CloneError (const 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...
 
- Public Member Functions inherited from ITableListener
virtual void ValueChangedEx (ITable *source, llvm::StringRef key, std::shared_ptr< nt::Value > value, unsigned int flags)
 Extended version of ValueChanged. More...
 

Protected Member Functions

virtual void SetPosition (float pos)
 Set the PWM value based on a position. More...
 
virtual float GetPosition () const
 Get the PWM value in terms of a position. More...
 
virtual void SetSpeed (float speed)
 Set the PWM value based on a speed. More...
 
virtual float GetSpeed () const
 Get the PWM value in terms of speed. More...
 
void ValueChanged (ITable *source, llvm::StringRef key, std::shared_ptr< nt::Value > value, bool isNew) override
 Called when a key-value pair is changed in a ITable. More...
 
void UpdateTable () override
 Update the table for this sendable object with the latest values.
 
void StartLiveWindowMode () override
 Start having this sendable object automatically respond to value changes reflect the value on the table.
 
void StopLiveWindowMode () override
 Stop having this sendable object automatically respond to value changes.
 
std::string GetSmartDashboardType () const override
 
void InitTable (std::shared_ptr< ITable > subTable) override
 Initializes a table for this sendable object. More...
 
std::shared_ptr< ITableGetTable () const override
 
- Protected Member Functions inherited from SensorBase
void AddToSingletonList ()
 Add sensor to the singleton list. More...
 

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
 
std::shared_ptr< ITablem_table
 
- Protected Attributes inherited from ErrorBase
Error m_error
 

Static Protected Attributes

static constexpr float kDefaultPwmPeriod = 5.05
 kDefaultPwmPeriod is in ms More...
 
static constexpr float kDefaultPwmCenter = 1.5
 kDefaultPwmCenter is the PWM range center in ms
 
static const int32_t kDefaultPwmStepsDown = 1000
 kDefaultPWMStepsDown is the number of PWM steps below the centerpoint
 
static const int32_t kPwmDisabled = 0
 
- Static Protected Attributes inherited from SensorBase
static void * m_digital_ports [kDigitalChannels]
 
static void * m_relay_ports [kRelayChannels]
 
static void * m_pwm_ports [kPwmChannels]
 
- Static Protected Attributes inherited from ErrorBase
static priority_mutex _globalErrorMutex
 
static Error _globalError
 

Additional Inherited Members

- Static Public Member Functions inherited from SensorBase
static void DeleteSingletons ()
 Delete all the singleton classes on the list. More...
 
static uint32_t GetDefaultSolenoidModule ()
 
static bool CheckSolenoidModule (uint8_t moduleNumber)
 Check that the solenoid module number is valid. More...
 
static bool CheckDigitalChannel (uint32_t channel)
 Check that the digital channel number is valid. More...
 
static bool CheckRelayChannel (uint32_t channel)
 Check that the digital channel number is valid. More...
 
static bool CheckPWMChannel (uint32_t channel)
 Check that the digital channel number is valid. More...
 
static bool CheckAnalogInput (uint32_t channel)
 Check that the analog input number is value. More...
 
static bool CheckAnalogOutput (uint32_t channel)
 Check that the analog output number is valid. More...
 
static bool CheckSolenoidChannel (uint32_t channel)
 Verify that the solenoid channel number is within limits. More...
 
static bool CheckPDPChannel (uint32_t channel)
 Verify that the power distribution channel number is within limits. More...
 
- Static Public Member Functions inherited from ErrorBase
static void SetGlobalError (Error::Code code, llvm::StringRef contextMessage, llvm::StringRef filename, llvm::StringRef function, uint32_t lineNumber)
 
static void SetGlobalWPIError (llvm::StringRef errorMessage, llvm::StringRef contextMessage, llvm::StringRef filename, llvm::StringRef function, uint32_t lineNumber)
 
static ErrorGetGlobalError ()
 Retrieve the current global error.
 
- Static Public Attributes inherited from SensorBase
static const uint32_t kDigitalChannels = 26
 
static const uint32_t kAnalogInputs = 8
 
static const uint32_t kAnalogOutputs = 2
 
static const uint32_t kSolenoidChannels = 8
 
static const uint32_t kSolenoidModules = 2
 
static const uint32_t kPwmChannels = 20
 
static const uint32_t kRelayChannels = 8
 
static const uint32_t kPDPChannels = 16
 
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 0-2000 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 0-2000 values as follows:

  • 2000 = maximum pulse width
  • 1999 to 1001 = linear scaling from "full forward" to "center"
  • 1000 = center value
  • 999 to 2 = linear scaling from "center" to "full reverse"
  • 1 = minimum pulse width (currently .5ms)
  • 0 = disabled (i.e. PWM output is held low)

Constructor & Destructor Documentation

PWM::PWM ( uint32_t  channel)
explicit

Allocate a PWM given a channel number.

Checks channel value range and allocates the appropriate channel. The allocation is only done to help users ensure that they don't double assign channels.

Parameters
channelThe PWM channel number. 0-9 are on-board, 10-19 are on the MXP port
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
eliminateDeadbandIf 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 ( ) const
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.
unsigned short PWM::GetRaw ( ) const
virtual

Get the PWM value directly from the hardware.

Read a raw value from a PWM channel.

Returns
Raw PWM control value.
std::string PWM::GetSmartDashboardType ( ) const
overrideprotectedvirtual
Returns
the string representation of the named data type that will be used by the smart dashboard for this sendable

Implements Sendable.

float PWM::GetSpeed ( ) const
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.
std::shared_ptr< ITable > PWM::GetTable ( ) const
overrideprotectedvirtual
Returns
the table that is currently associated with the sendable

Implements Sendable.

void PWM::InitTable ( std::shared_ptr< ITable subtable)
overrideprotectedvirtual

Initializes a table for this sendable object.

Parameters
subtableThe table to put the values in.

Implements Sendable.

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
maxThe Minimum pwm value
deadbandMaxThe high end of the deadband range
centerThe center speed (off)
deadbandMinThe low end of the deadband range
minThe 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
maxThe max PWM pulse width in ms
deadbandMaxThe high end of the deadband range pulse width in ms
centerThe center (off) pulse width in ms
deadbandMinThe low end of the deadband pulse width in ms
minThe minimum pulse width in ms
void PWM::SetPeriodMultiplier ( PeriodMultiplier  mult)

Slow down the PWM signal for old devices.

Parameters
multThe 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
posThe position to set the servo between 0.0 and 1.0.
void PWM::SetRaw ( unsigned short  value)
virtual

Set the PWM value directly to the hardware.

Write a raw value to a PWM channel.

Parameters
valueRaw PWM value.
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
speedThe speed to set the speed controller between -1.0 and 1.0.

Reimplemented in SafePWM.

void PWM::ValueChanged ( ITable source,
llvm::StringRef  key,
std::shared_ptr< nt::Value value,
bool  isNew 
)
overrideprotectedvirtual

Called when a key-value pair is changed in a ITable.

Parameters
sourcethe table the key-value pair exists in
keythe key associated with the value that changed
valuethe new value
isNewtrue if the key did not previously exist in the table, otherwise it is false

Implements ITableListener.

Member Data Documentation

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.


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