Capacitive Sensing Firmware Library
Platform Middleware

Detailed Description

Capacitive sensing firmware library for Silicon Labs MCUs.

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.

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

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.

Enumerations

enum CSLIB_noiseLevels {
low = 1,
mid = 2,
high = 3
}
Defines all noise characterization states the CSLIB will use for characterization.

Functions

uint8_t CSLIB_anySensorDebounceActive (void)
uint8_t CSLIB_anySensorSingleActive (void)
void CSLIB_baselineInitDisableCB (void)
void CSLIB_baselineInitEnableCB (void)
void CSLIB_checkTimerCB (void)
void CSLIB_configureSensorForActiveModeCB (void)
void CSLIB_configureSensorForSleepModeCB (void)
void CSLIB_configureTimerForActiveModeCB (void)
void CSLIB_configureTimerForSleepModeCB (void)
void CSLIB_enterLowPowerStateCB (void)
uint16_t CSLIB_getNoiseAdjustedSensorData (uint8_t index)
uint16_t CSLIB_getNormalizedDelta (uint8_t sensor_index, uint16_t flood_level)
int16_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)
void CSLIB_lowPowerUpdateCheckAppBuilder (void)
void CSLIB_lowPowerUpdateExitAppBuilder (void)
uint16_t CSLIB_nodeGetRaw (uint8_t sensorIndex, uint8_t bufferIndex)
void CSLIB_nodePushRaw (uint8_t index, uint32_t newValue)
void CSLIB_resetSensorStruct (uint8_t sensorIndex, uint16_t fillValue)
uint32_t CSLIB_scanSensorCB (uint8_t index)
void CSLIB_update (void)

Variables

uint16_t CSLIB_activeModePeriod
Sets the scan period in ms for active mode scanning. Defaults to DEF_ACTIVE_MODE_PERIOD.
const uint8_t CSLIB_activeThreshold []
Array storring percentages within touch deltas below which touch events are qualified.
const uint8_t CSLIB_averageTouchDelta []
Array of expected conversion output codes between inactive and active sensor states.
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.
const uint8_t CSLIB_inactiveThreshold []
Array storring percentages within touch deltas below which touch release events are qualified.
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.
uint8_t timerTick
Global counter incremented by the system timer.

Enumeration Type Documentation

enum CSLIB_noiseLevels

Defines all noise characterization states the CSLIB will use for characterization.

Enumerator
low

Interference should have negligible impact on sensing.

mid

Interference forces system to qualify touches conservatively.

high

Interference forces entrance into no confidence mode if enabled.

Definition at line 434 of file cslib.h .

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
void CSLIB_baselineInitDisableCB ( void )

Restore capacitive sensing config to operational state

This function reverts any baseline-related capactive sensing config.

void CSLIB_baselineInitEnableCB ( void )

Modify capacitive sense config for baseline initialization

Saves configuration state and makes device-level modifications appropriate to baseline initialization using the scanSensor() function.

void CSLIB_checkTimerCB ( void )

Check wake sources

This function examines the system timer to check for wake events.

Check wake sources

This callback function examines the system timer to check for wake events.

void CSLIB_configureSensorForActiveModeCB ( void )

Callback to confiure sensors for active mode

Callback routine to configure sensors for active mode scanning.

void CSLIB_configureSensorForSleepModeCB ( void )

Callback to configure sensors for sleep mode

Callback routine used if low power mode is included in build, this function configures the capacitive sensing block and inputs for sleep mode.

void CSLIB_configureTimerForActiveModeCB ( void )

Callback to configure timer for active mode scanning

Configures the timer to initiate a scan as defined by active mode scan period.

void CSLIB_configureTimerForSleepModeCB ( void )

Configure timer for sleep mode

If low power mode is included in build, this function sets the wake-up event to the sleep mode scan period.

void CSLIB_enterLowPowerStateCB ( void )

Callback to enter low power mode

If low power mode is included in build, this function mode-switches the core to a low power state.

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_getNormalizedDelta ( uint8_t sensor_index,
uint16_t flood_level
)

Get baseline-adjusted, noise-adjusted touch delta

Parameters
sensor_index Index into sensor node struct
flood_level additional value that can be subtracted in addition to baseline

Returns value that is raw or filtered data minus the sensor's baseline. flood_level can be used to remove additional margin along with baseline.

@ return Absolute delta between baseline and raw/filtered data

int16_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 signed 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.

void CSLIB_lowPowerUpdateCheckAppBuilder ( void )

Checks timing and possibly enters low power mode

This function checks the time in the system relative to active mode scan period timing.

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. The calling system stack will intiate low power entry.

void CSLIB_lowPowerUpdateExitAppBuilder ( void )

Exits low power state for CSLIB

This function is called by the interface layer when it detects a threshold crossing interrupt. The function will return to normal CSLIB operation.

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,
uint32_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.

uint32_t CSLIB_scanSensorCB ( 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
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.