Detailed Description

Capacitive sensing firmware library for Silicon Labs MCUs and SoCs.

Introduction

The capacitive sensing library provides pre-compiled code set that performs touch qualification, filtering, and state maintanence for capacitive sensing-enabled Silicon Laboratories MCUs and SoCs.

The library functions using calls into a device layer that interfaces with hardware peripherals.

Data Structures
struct	SensorStruct_t
	Stores all runtime values for an enabled capacitive sensor. More...

union	SI_UU32
	Union used to address upper bytes of 32-bit exponential average easily. More...

Macros
#define	DEBOUNCE_ACTIVE_MASK 0x80
	Bit that is set when sensor is qualified active.

#define	DEF_SENSOR_BUFFER_SIZE 2
	Defines the depth of the raw buffer. Note: this value should not be changed.

#define	SINGLE_ACTIVE_MASK 0x40
	Bit that is set when sensor is candidate active.

Typedefs
typedef union SI_UU32	SI_UU32_t
	Union used to address upper bytes of 32-bit exponential average easily.

Functions
uint8_t	CSLIB_anySensorDebounceActive (void)

uint8_t	CSLIB_anySensorSingleActive (void)

uint16_t	CSLIB_getNoiseAdjustedSensorData (uint8_t index)

uint16_t	CSLIB_getUnpackedTouchDelta (uint8_t index)

void	CSLIB_initHardware (void)

void	CSLIB_initLibrary (void)

uint8_t	CSLIB_isSensorDebounceActive (uint8_t index)

uint8_t	CSLIB_isSensorSingleActive (uint8_t index)

void	CSLIB_lowPowerUpdate (void)

uint16_t	CSLIB_nodeGetRaw (uint8_t sensorIndex, uint8_t bufferIndex)

void	CSLIB_nodePushRaw (uint8_t index, uint16_t newValue)

void	CSLIB_resetSensorStruct (uint8_t sensorIndex, uint16_t fillValue)

void	CSLIB_update (void)

uint16_t	scanSensor (uint8_t index)

Variables
uint16_t	CSLIB_activeModePeriod
	Sets the scan period in ms for active mode scanning. Defaults to DEF_ACTIVE_MODE_PERIOD.

uint8_t	CSLIB_buttonDebounce
	Sets the number of consecutive values above/below threshold before button is qualified/disqualified. Defaults to DEF_BUTTON_DEBOUNCE.

uint16_t	CSLIB_countsBeforeSleep
	Sets the number of consecutive scans without a single qualified touch before entering sleep mode.

uint8_t	CSLIB_freeRunSetting
	Configures whether system goes to sleep between scans in active mode. 1 means that the system is in free run mode and will not go to sleep. 0 means that the system will take a single scan within an active mode scan period and will then enter sleep once CSLIB_lowPowerUpdate() is called. The system will stay asleep until the next active mode scan period begins.

SensorStruct_t	CSLIB_node []
	Sensor node data structure.

uint8_t	CSLIB_numSensors
	Size of the sensor node struct, should only be changed at compile time by editing DEF_NUM_SENSORS.

uint8_t	CSLIB_sensorBufferSize
	Size of raw data buffers within sensor node struct elements, should not be changed.

uint8_t	CSLIB_sleepModeEnable
	Sets whether the system is allowed to ever use sleep mode scanning. If set to 0, the system will always remain in active mode. If set to 1, the system is allowed to perform sleep mode scanning when conditions permit it.

uint16_t	CSLIB_sleepModePeriod
	Sets the scan period in ms for sleep mode scanning. Defaults to DEF_ACTIVE_MODE_PERIOD.

uint16_t	CSLIB_systemNoiseAverage
	Describes average interference seen as a percentage of the average touch delta. 100 would mean that average sample to sample interference is equal to the average touch delta configured in the system.

uint8_t	disable_sleep_and_stall
	Bit that can be set to disable entrance to sleep, overriding timers.

uint8_t	noise_level
	Stores interference characterization level, 0 being lowest and 3 being highest.

Function Documentation

uint8_t CSLIB_anySensorDebounceActive ( void )

Checks to see if any enabled sensor is debounce active

Checks to see if any enabled sensor is qualified active, meaning that the data from the sensor on this input has risen above the active threshold for a consecutive number of samples equaling at least the value defined by DEF_DEBOUNCE_COUNTS.

Returns: 1 if any enabled sensor is debounce active, 0 otherwise

uint8_t CSLIB_anySensorSingleActive ( void )

Checks to see if any enabled sensor is single active

This function checks the SINGLE_ACTIVE_MASK in the sensor node structure for all enabled sensors. If any sensor's SINGLE_ACTIVE_MASK is set, meaning that the sensor is a candidate active sensor, the the function returns TRUE. Otherwise it returns FALSE.

Returns: 1 if any sensor is active, 0 otherwise

uint16_t CSLIB_getNoiseAdjustedSensorData ( uint8_t index )

Returns raw or filtered sensor data, based on characterized interference

Parameters

index Sensor node element whose data is to be read

This function either returns the newest raw data for a sensor, or the newest filtered data for a sensor, depending on which data type the interference characterization algorithm determines to be necessary to show current sensor state. In low interference environments, raw data will be returned. In higher interference states, filtered data will be returned.

Returns: sensor data from sensor node struct defined index

uint16_t CSLIB_getUnpackedTouchDelta ( uint8_t index )

Read touch delta from sensor node struct and expand from 8-bit value

Parameters

index Designates the sensor touch delta to be read

This function returns the 8-bit compressed touch delta as an uncompressed 16 bit value.

Returns: 16-bit touch delta value of a sensor defined by index

void CSLIB_initHardware ( void )

Initializes capacitive sensing-related peripherals

This function calls into the library, which in turn calls into the device layer functions initializing the sensing and timing hardware used during capacitive sensing conversions.

void CSLIB_initLibrary ( void )

Initializes capacitive sensing state variables

This function resets all state variables in the sensor node struct and library-internal state variables to default.

uint8_t CSLIB_isSensorDebounceActive ( uint8_t index )

Checks if a sensor is debounce active

Parameters

index into sensor node element to be checked

This checks to see if any enabled sensor is a qualified active sensor.

Returns: 1 if element selected by index is debounce active, 0 otherwise

uint8_t CSLIB_isSensorSingleActive ( uint8_t index )

Checks if a sensor is single active

Parameters

index into sensor node element to be checked

This checks to see if any enabled sensor is a candidate active sensor.

Returns: 1 if element selected by index is single active, 0 otherwise

void CSLIB_lowPowerUpdate ( void )

Checks timing and possibly enters low power mode

This function checks the time in the system relative to active mode scan period timing. It should be called in the firmware project's main() while(1) loop.

If FREE_RUN_SETTING is set to 0, the function will enter low power until the next active mode scan period.

If FREE_RUN_SETTING is set to 1, the function will exit, allowing for another iteration in the main() loop.

If CSLIB_lowPowerUpdate() finds that no qualified touches have been found in a time specified by COUNTS_BEFORE_SLEEP multiplied by ACTIVE_MODE_SCAN_PERIOD, the function initializes the system to run in its sleep scanning mode and enters a low power state.

uint16_t CSLIB_nodeGetRaw	(	uint8_t	sensorIndex,
		uint8_t	bufferIndex
	)

Reads a node structure sensor's raw buffer value

Parameters

sensorIndex	The element of the sensor node structure
bufferIndex	The element inside the sensor node element's raw data buffer

This function can be used to read values in the raw data buffer at bufferIndex of an enabled sensor specified by sensorIndex.

Note: sensorIndex should not exceed the value defined by CSLIB_numSensors; bufferIndex should not exceed the value defined by CSLIB_sensorBufferSize

Returns: the value in the raw data buffer

void CSLIB_nodePushRaw	(	uint8_t	index,
		uint16_t	newValue
	)

Pushes new sensor sample into sensor node buffer

Parameters

index	index into sensor node array
newValue	value to be pushed at index

This function is used by the device layer of code that interfaces with capacitive sensing hardware. When CSLIB_update() calls into the device layer to convert a new sample set using scanSensor(), the device layer implementation of scanSensor() should use this routine to push newly converted samples into the sensor node structure for processing within the library.

void CSLIB_resetSensorStruct	(	uint8_t	sensorIndex,
		uint16_t	fillValue
	)

Resets an element of the sensor node struct back to defaults

Parameters

sensorIndex	index of sensor node struct to reset
fillValue	value to be used when filling raw data buffer

This function is called during initialization to reset the sensor at node sensorIndex back to back to its power-on state.

void CSLIB_update ( void )

Scans capacitive sensing inputs, processes and updates state variables

This function should be called in a firmware project's main() loop. The function will execute a capacitive sensing scan sequence, filter samples, examine samples for qualified touches, and update other state variables.

uint16_t scanSensor ( uint8_t index )

Performs capacitive sensing conversion on a sensor

Parameters

index The sensor to be scanned, corresponds to sensor node struct

This device layer function is called from within library code after CSLIB_update() is called in the main loop. The function is responsible for any configuration of the capacitive sensing block necessary to perform the scan.

Returns: the newly converted capacitive sensing output

Detailed Description

Introduction

Data Structures

Macros

Typedefs

Functions

Variables

Function Documentation