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Description
Pulse Width Modulation (PWM) is a technique of encoding a pulsed signal so as to control the ratio of on to off by switching the signal between on and off at a very high rate.
This on and off switching allows control of the average power supplied to the load and therefore gives fine grained control of things such as motor speeds, lamp dimming and heating elements.
PWM is also used in many low power applications as well such as controlling servo motors and can even by used for audio applications such as class D amplifiers.
This unit deals with the usage of PWM for control applications (for audio applications see the Audio unit) and provides methods to control the state, frequency, duty cycle, range and mode of PWM host controllers. Not all devices support all of these concepts so this API includes a properties function to allow obtaining information about a PWM device and its capabilities.
Constants
To be documented
Type definitions
To be documented
Public variables
To be documented
Function declarations
Initialization functions
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procedure PWMInit;
Description: Initialize the PWM unit and PWM device table
| Note
|
Called only during system startup
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PWM functions
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function PWMDeviceStart(PWM:PPWMDevice):LongWord;
Description: Start the specified PWM device
| PWM
|
The PWM device to start
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| Return
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ERROR_SUCCESS if completed or another error code on failure
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function PWMDeviceStop(PWM:PPWMDevice):LongWord;
Description: Stop the specified PWM device
| PWM
|
The PWM device to stop
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| Return
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ERROR_SUCCESS if completed or another error code on failure
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function PWMDeviceWrite(PWM:PPWMDevice; Value:LongWord):LongWord;
Description: Write a value to the specified PWM device
| PWM
|
The PWM device to write to
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| Value
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The value to write
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| Return
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ERROR_SUCCESS if completed or another error code on failure
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| Note
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The exact meaning of value may depend on the device and other configured options, in many cases the value will represent the "on" time of each pulse with regard to the duty cycle of the waveform output by the device
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function PWMDeviceGetGPIO(PWM:PPWMDevice):LongWord;
Description: Get the GPIO pin used by the specified PWM device
| PWM
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The PWM device to get the GPIO pin from
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| Return
|
The current GPIO pin or GPIO_PIN_UNKNOWN on failure
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function PWMDeviceSetGPIO(PWM:PPWMDevice; GPIO:LongWord):LongWord;
Description: Set the GPIO pin used by the specified PWM device
| PWM
|
The PWM device to set the GPIO pin for
|
| GPIO
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The GPIO pin to set (eg GPIO_PIN_12)
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| Return
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ERROR_SUCCESS if completed or another error code on failure
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function PWMDeviceGetMode(PWM:PPWMDevice):LongWord;
Description: Get the current mode of the specified PWM device
| PWM
|
The PWM device to get the mode from
|
| Return
|
The current mode or a default value of PWM_MODE_MARKSPACE
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function PWMDeviceSetMode(PWM:PPWMDevice; Mode:LongWord):LongWord;
Description: Set the current mode for the specified PWM device
| PWM
|
The PWM device to set the mode for
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| Mode
|
The mode value to set (eg PWM_MODE_MARKSPACE)
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| Return
|
ERROR_SUCCESS if completed or another error code on failure
|
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function PWMDeviceGetRange(PWM:PPWMDevice):LongWord;
Description: Get the current range of the specified PWM device
| PWM
|
The PWM device to get the range from
|
| Return
|
The current range or 0 on failure
|
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function PWMDeviceSetRange(PWM:PPWMDevice; Range:LongWord):LongWord;
Description: Set the current range for the specified PWM device
| PWM
|
The PWM device to set the clock rate for
|
| Range
|
The range value to set
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| Return
|
ERROR_SUCCESS if completed or another error code on failure
|
| Note
|
The exact meaning of range may depend on the device and other configured options, in many cases the range will represent the period of one full cycle of the waveform output by the device
|
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function PWMDeviceGetFrequency(PWM:PPWMDevice):LongWord;
Description: Get the clock frequency of the specified PWM device
| PWM
|
The PWM device to get the clock frequency from
|
| Return
|
The clock frequency in Hz or 0 on failure
|
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function PWMDeviceSetFrequency(PWM:PPWMDevice; Frequency:LongWord):LongWord;
Description: Set the clock frequency for the specified PWM device
| PWM
|
The PWM device to set the clock frequency for
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| Frequency
|
The clock frequency to set in Hz
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| Return
|
ERROR_SUCCESS if completed or another error code on failure
|
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function PWMDeviceGetPolarity(PWM:PPWMDevice):LongWord;
Description: Get the current polarity of the specified PWM device
| PWM
|
The PWM device to get the polarity from
|
| Return
|
The current polarity or a default value of PWM_POLARITY_NORMAL
|
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function PWMDeviceSetPolarity(PWM:PPWMDevice; Polarity:LongWord):LongWord;
Description: Set the current polarity for the specified PWM device
| PWM
|
The PWM device to set the polarity for
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| Polarity
|
The polarity value to set (eg PWM_POLARITY_NORMAL)
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| Return
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ERROR_SUCCESS if completed or another error code on failure
|
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function PWMDeviceConfigure(PWM:PPWMDevice; DutyNS,PeriodNS:LongWord):LongWord;
Description: Set the configuration of the specified PWM device
| PWM
|
The PWM device to set the configuration for
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| DutyNS
|
The "on" time part of the cycle (Nanoseconds)
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| PeriodNS
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The duration of one full cycle (Nanoseconds)
|
| Return
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ERROR_SUCCESS if completed or another error code on failure
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function PWMDeviceProperties(PWM:PPWMDevice; Properties:PPWMProperties):LongWord;
Description: Get the properties for the specified PWM device
| PWM
|
The PWM device to get properties from
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| Properties
|
Pointer to a TPWMProperties structure to fill in
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| Return
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ERROR_SUCCESS if completed or another error code on failure
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function PWMDeviceCreate:PPWMDevice;
Description: Create a new PWM entry
| Return
|
Pointer to new PWM entry or nil if PWM could not be created
|
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function PWMDeviceCreateEx(Size:LongWord):PPWMDevice;
Description: Create a new PWM entry
| Size
|
Size in bytes to allocate for new PWM (Including the PWM entry)
|
| Return
|
Pointer to new PWM entry or nil if PWM could not be created
|
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function PWMDeviceDestroy(PWM:PPWMDevice):LongWord;
Description: Destroy an existing PWM entry
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function PWMDeviceRegister(PWM:PPWMDevice):LongWord;
Description: Register a new PWM in the PWM table
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function PWMDeviceDeregister(PWM:PPWMDevice):LongWord;
Description: Deregister a PWM from the PWM table
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function PWMDeviceFind(PWMId:LongWord):PPWMDevice;
Description: To be documented
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function PWMDeviceFindByName(const Name:String):PPWMDevice; inline;
Description: To be documented
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function PWMDeviceFindByDescription(const Description:String):PPWMDevice; inline;
Description: To be documented
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function PWMDeviceEnumerate(Callback:TPWMEnumerate; Data:Pointer):LongWord;
Description: To be documented
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function PWMDeviceNotification(PWM:PPWMDevice; Callback:TPWMNotification; Data:Pointer; Notification,Flags:LongWord):LongWord;
Description: To be documented
RTL PWM functions
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function SysPWMAvailable:Boolean;
Description: Check if a PWM device is available
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function SysPWMStart:LongWord;
Description: Start the default PWM device
| Return
|
ERROR_SUCCESS if completed or another error code on failure
|
[Expand]
function SysPWMStop:LongWord;
Description: Stop the default PWM device
| Return
|
ERROR_SUCCESS if completed or another error code on failure
|
[Expand]
function SysPWMWrite(Value:LongWord):LongWord;
Description: Write a value to the default PWM device
| Value
|
The value to write
|
| Return
|
ERROR_SUCCESS if completed or another error code on failure
|
| Note
|
The exact meaning of value may depend on the device and other configured options, in many cases the value will represent the "on" time of each pulse with regard to the duty cycle of the waveform output by the device
|
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function SysPWMSetMode(Mode:LongWord):LongWord;
Description: Set the mode for the default PWM device
| Mode
|
The mode value to set (eg PWM_MODE_MARKSPACE)
|
| Return
|
ERROR_SUCCESS if completed or another error code on failure
|
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function SysPWMSetRange(Range:LongWord):LongWord;
Description: Set the range for the default PWM device
| Range
|
The range value to set
|
| Return
|
ERROR_SUCCESS if completed or another error code on failure
|
| Note
|
The exact meaning of range may depend on the device and other configured options, in many cases the range will represent the period of one full cycle of the waveform output by the device
|
[Expand]
function SysPWMSetFrequency(Frequency:LongWord):LongWord;
Description: Set the clock frequency for the default PWM device
| Frequency
|
The frequency to set in Hz
|
| Return
|
ERROR_SUCCESS if completed or another error code on failure
|
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function SysPWMConfigure(DutyNS,PeriodNS:LongWord):LongWord;
Description: Set the configuration of the default PWM device
| DutyNS
|
The "on" time part of the cycle (Nanoseconds)
|
| PeriodNS
|
The duration of one full cycle (Nanoseconds)
|
| Return
|
ERROR_SUCCESS if completed or another error code on failure
|
PWM helper functions
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function PWMGetCount:LongWord; inline;
Description: Get the current PWM count
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function PWMDeviceGetDefault:PPWMDevice; inline;
Description: Get the current default PWM device
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function PWMDeviceSetDefault(PWM:PPWMDevice):LongWord;
Description: Set the current default PWM device
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function PWMDeviceCheck(PWM:PPWMDevice):PPWMDevice;
Description: Check if the supplied PWM is in the PWM table
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procedure PWMLog(Level:LongWord; PWM:PPWMDevice; const AText:String);
Description: To be documented
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procedure PWMLogInfo(PWM:PPWMDevice; const AText:String); inline;
Description: To be documented
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procedure PWMLogError(PWM:PPWMDevice; const AText:String); inline;
Description: To be documented
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procedure PWMLogDebug(PWM:PPWMDevice; const AText:String); inline;
Description: To be documented
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