Qei_api

Functions
void	QEIEnable (uint32_t ui32Base)
void	QEIDisable (uint32_t ui32Base)
void	QEIConfigure (uint32_t ui32Base, uint32_t ui32Config, uint32_t ui32MaxPosition)
uint32_t	QEIPositionGet (uint32_t ui32Base)
void	QEIPositionSet (uint32_t ui32Base, uint32_t ui32Position)
int32_t	QEIDirectionGet (uint32_t ui32Base)
bool	QEIErrorGet (uint32_t ui32Base)
void	QEIVelocityEnable (uint32_t ui32Base)
void	QEIVelocityDisable (uint32_t ui32Base)
void	QEIVelocityConfigure (uint32_t ui32Base, uint32_t ui32PreDiv, uint32_t ui32Period)
uint32_t	QEIVelocityGet (uint32_t ui32Base)
void	QEIIntRegister (uint32_t ui32Base, void(*pfnHandler)(void))
void	QEIIntUnregister (uint32_t ui32Base)
void	QEIIntEnable (uint32_t ui32Base, uint32_t ui32IntFlags)
void	QEIIntDisable (uint32_t ui32Base, uint32_t ui32IntFlags)
uint32_t	QEIIntStatus (uint32_t ui32Base, bool bMasked)
void	QEIIntClear (uint32_t ui32Base, uint32_t ui32IntFlags)

Detailed Description

Function Documentation

void QEIConfigure	(	uint32_t	ui32Base,
		uint32_t	ui32Config,
		uint32_t	ui32MaxPosition
	)

Configures the quadrature encoder.

Parameters

ui32Base	is the base address of the quadrature encoder module.
ui32Config	is the configuration for the quadrature encoder. See below for a description of this parameter.
ui32MaxPosition	specifies the maximum position value.

This function configures the operation of the quadrature encoder. The ui32Config parameter provides the configuration of the encoder and is the logical OR of several values:

• QEI_CONFIG_CAPTURE_A or QEI_CONFIG_CAPTURE_A_B specify if edges on channel A or on both channels A and B should be counted by the position integrator and velocity accumulator.
• QEI_CONFIG_NO_RESET or QEI_CONFIG_RESET_IDX specify if the position integrator should be reset when the index pulse is detected.
• QEI_CONFIG_QUADRATURE or QEI_CONFIG_CLOCK_DIR specify if quadrature signals are being provided on ChA and ChB, or if a direction signal and a clock are being provided instead.
• QEI_CONFIG_NO_SWAP or QEI_CONFIG_SWAP to specify if the signals provided on ChA and ChB should be swapped before being processed.

ui32MaxPosition is the maximum value of the position integrator and is the value used to reset the position capture when in index reset mode and moving in the reverse (negative) direction.

Returns

None.

int32_t QEIDirectionGet

(

uint32_t

ui32Base

)

Gets the current direction of rotation.

Parameters

ui32Base

is the base address of the quadrature encoder module.

This function returns the current direction of rotation. In this case, current means the most recently detected direction of the encoder; it may not be presently moving but this is the direction it last moved before it stopped.

Returns

Returns 1 if moving in the forward direction or -1 if moving in the reverse direction.

void QEIDisable

(

uint32_t

ui32Base

)

Disables the quadrature encoder.

Parameters

ui32Base

is the base address of the quadrature encoder module.

This function disables operation of the quadrature encoder module.

Returns

None.

void QEIEnable

(

uint32_t

ui32Base

)

Enables the quadrature encoder.

Parameters

ui32Base

is the base address of the quadrature encoder module.

This function enables operation of the quadrature encoder module. The module must be configured before it is enabled.

See also

QEIConfigure()

Returns

None.

bool QEIErrorGet

(

uint32_t

ui32Base

)

Gets the encoder error indicator.

Parameters

ui32Base

is the base address of the quadrature encoder module.

This function returns the error indicator for the quadrature encoder. It is an error for both of the signals of the quadrature input to change at the same time.

Returns

Returns true if an error has occurred and false otherwise.

void QEIIntClear	(	uint32_t	ui32Base,
		uint32_t	ui32IntFlags
	)

Clears quadrature encoder interrupt sources.

Parameters

ui32Base	is the base address of the quadrature encoder module.
ui32IntFlags	is a bit mask of the interrupt sources to be cleared. This parameter can be any of the QEI_INTERROR, QEI_INTDIR, QEI_INTTIMER, or QEI_INTINDEX values.

The specified quadrature encoder interrupt sources are cleared, so that they no longer assert. This function must be called in the interrupt handler to keep the interrupt from being triggered again immediately upon exit.

Note

Because there is a write buffer in the Cortex-M processor, it may take several clock cycles before the interrupt source is actually cleared. Therefore, it is recommended that the interrupt source be cleared early in the interrupt handler (as opposed to the very last action) to avoid returning from the interrupt handler before the interrupt source is actually cleared. Failure to do so may result in the interrupt handler being immediately reentered (because the interrupt controller still sees the interrupt source asserted).

Returns

None.

void QEIIntDisable	(	uint32_t	ui32Base,
		uint32_t	ui32IntFlags
	)

Disables individual quadrature encoder interrupt sources.

Parameters

ui32Base	is the base address of the quadrature encoder module.
ui32IntFlags	is a bit mask of the interrupt sources to be disabled. This parameter can be any of the QEI_INTERROR, QEI_INTDIR, QEI_INTTIMER, or QEI_INTINDEX values.

This function disables the indicated quadrature encoder interrupt sources. Only the sources that are enabled can be reflected to the processor interrupt; disabled sources have no effect on the processor.

Returns

None.

void QEIIntEnable	(	uint32_t	ui32Base,
		uint32_t	ui32IntFlags
	)

Enables individual quadrature encoder interrupt sources.

Parameters

ui32Base	is the base address of the quadrature encoder module.
ui32IntFlags	is a bit mask of the interrupt sources to be enabled. Can be any of the QEI_INTERROR, QEI_INTDIR, QEI_INTTIMER, or QEI_INTINDEX values.

This function enables the indicated quadrature encoder interrupt sources. Only the sources that are enabled can be reflected to the processor interrupt; disabled sources have no effect on the processor.

Returns

None.

void QEIIntRegister	(	uint32_t	ui32Base,
		void(*)(void)	pfnHandler
	)

Registers an interrupt handler for the quadrature encoder interrupt.

Parameters

ui32Base	is the base address of the quadrature encoder module.
pfnHandler	is a pointer to the function to be called when the quadrature encoder interrupt occurs.

This function registers the handler to be called when a quadrature encoder interrupt occurs. This function enables the global interrupt in the interrupt controller; specific quadrature encoder interrupts must be enabled via QEIIntEnable(). It is the interrupt handler's responsibility to clear the interrupt source via QEIIntClear().

See also

IntRegister() for important information about registering interrupt handlers.

Returns

None.

uint32_t QEIIntStatus	(	uint32_t	ui32Base,
		bool	bMasked
	)

Gets the current interrupt status.

Parameters

ui32Base	is the base address of the quadrature encoder module.
bMasked	is false if the raw interrupt status is required and true if the masked interrupt status is required.

This function returns the interrupt status for the quadrature encoder module. Either the raw interrupt status or the status of interrupts that are allowed to reflect to the processor can be returned.

Returns

Returns the current interrupt status, enumerated as a bit field of QEI_INTERROR, QEI_INTDIR, QEI_INTTIMER, and QEI_INTINDEX.

void QEIIntUnregister

(

uint32_t

ui32Base

)

Unregisters an interrupt handler for the quadrature encoder interrupt.

Parameters

ui32Base

is the base address of the quadrature encoder module.

This function unregisters the handler to be called when a quadrature encoder interrupt occurs. This function also masks off the interrupt in the interrupt controller so that the interrupt handler no longer is called.

See also

IntRegister() for important information about registering interrupt handlers.

Returns

None.

uint32_t QEIPositionGet

(

uint32_t

ui32Base

)

Gets the current encoder position.

Parameters

ui32Base

is the base address of the quadrature encoder module.

This function returns the current position of the encoder. Depending upon the configuration of the encoder, and the incident of an index pulse, this value may or may not contain the expected data (that is, if in reset on index mode, if an index pulse has not been encountered, the position counter is not yet aligned with the index pulse).

Returns

The current position of the encoder.

void QEIPositionSet	(	uint32_t	ui32Base,
		uint32_t	ui32Position
	)

Sets the current encoder position.

Parameters

ui32Base	is the base address of the quadrature encoder module.
ui32Position	is the new position for the encoder.

This function sets the current position of the encoder; the encoder position is then measured relative to this value.

Returns

None.

void QEIVelocityConfigure	(	uint32_t	ui32Base,
		uint32_t	ui32PreDiv,
		uint32_t	ui32Period
	)

Configures the velocity capture.

Parameters

ui32Base	is the base address of the quadrature encoder module.
ui32PreDiv	specifies the predivider applied to the input quadrature signal before it is counted; can be one of QEI_VELDIV_1, QEI_VELDIV_2, QEI_VELDIV_4, QEI_VELDIV_8, QEI_VELDIV_16, QEI_VELDIV_32, QEI_VELDIV_64, or QEI_VELDIV_128.
ui32Period	specifies the number of clock ticks over which to measure the velocity; must be non-zero.

This function configures the operation of the velocity capture portion of the quadrature encoder. The position increment signal is predivided as specified by ui32PreDiv before being accumulated by the velocity capture. The divided signal is accumulated over ui32Period system clock before being saved and resetting the accumulator.

Returns

None.

void QEIVelocityDisable

(

uint32_t

ui32Base

)

Disables the velocity capture.

Parameters

ui32Base

is the base address of the quadrature encoder module.

This function disables operation of the velocity capture in the quadrature encoder module.

Returns

None.

void QEIVelocityEnable

(

uint32_t

ui32Base

)

Enables the velocity capture.

Parameters

ui32Base

is the base address of the quadrature encoder module.

This function enables operation of the velocity capture in the quadrature encoder module. The module must be configured before velocity capture is enabled.

See also

QEIVelocityConfigure() and QEIEnable()

Returns

None.

uint32_t QEIVelocityGet

(

uint32_t

ui32Base

)

Gets the current encoder speed.

Parameters

ui32Base

is the base address of the quadrature encoder module.

This function returns the current speed of the encoder. The value returned is the number of pulses detected in the specified time period; this number can be multiplied by the number of time periods per second and divided by the number of pulses per revolution to obtain the number of revolutions per second.

Returns

Returns the number of pulses captured in the given time period.