COMPB Event Trigger¶

Description¶

Use COMPB to trigger Event Handler Code

This resource uses COMPB (low-power clocked comparator) to trigger an Event Handler Code task code block. Triggering can either occur at high or low level (no transition required) or at rising or falling edge on the COMPB output.

This can typically be used to monitor analog signals such as:

Power supply voltage
Analog sensor output

The COMPB peripheral must be enabled separately using the COMPB resource.

The trigger can be set up from within the Initialization Code , Execution Code or Event Handler Code task code blocks.

The trigger is one-shot.

Event Trigger Mapping¶

The CC13x2/CC26x2 and CC13x4/CC26x4 chip families support up to 3 event triggers in total per project. The Code Generator Panel displays an error message if this number is exceeded.

Access the Task Panel to map event trigger(s) to Event Handler Code task code blocks:

Ensure that one or more event trigger resources are enabled
Below these resources, select the number of simultaneous event triggers for the task
Map the event index(es) to Event Handler Code task code blocks. The event indexes start at 0 for each task.

While the number of event triggers and mapping of event indexes to task code blocks are static, the event indexes can be reused for different types of event triggers. For example, it is possible to alternate between a timer trigger and a GPIO trigger for one event index.

If a new event trigger is set up using an already active event index, the previously set up event trigger is cancelled.

The Termination Code must call evhCancelTrigger() for each used event index, so that the last set up event triggers do not occur after the task has been stopped.

Trigger Timing¶

Typical startup delays, from the COMPB event trigger to execution of the Event Handler Code task code block, are shown in the tables below.

For startup to low-power mode:

Scenario	No clock in standby mode	SCLK_LF in standby mode*
From standby mode, SCLK_MF clock not running	32 us	47 - 77 us
From standby mode, SCLK_MF clock already running	30 us	45 - 75 us
Trigger occurs while Sensor Controller runs other code	24 us or more (already running code must finish)

For startup to active mode:

Scenario	No clock in standby mode	SCLK_LF in standby mode*
From standby mode, SCLK_HF clock not running	145 - 200 us	145 - 215 us
From standby mode, SCLK_HF clock already running	7 us	24 - 54 us
Trigger occurs while Sensor Controller runs other code	4 us or more (already running code must finish)

* SCLK_LF is used in standby mode when one or more of these resources are enabled:

Reference DAC
RTC Multi-Event Capture
Timer 0 Event Trigger
Timer 1 Event Trigger

Examples¶

Initialization Code¶

// Connect sensor output to COMPB
compbSelectGpioInput(AUXIO_A_SENSOR);

// Enable COMPB with reference = VDDS/2
compbEnable(COMPB_REF_VDDS_DIV2);

// The COMPB output will be valid after 10 cycles on the 32 kHz clock, so use the timer event trigger
// to wait for this. We need to round up to account for timer event trigger precision and rounding.
evhSetupTimer1Trigger(0, 3, 0); // 750 us
state.initDone = 0;

Event Handler Code A¶

// The first execution (triggered by the timer) must initialize the trigger level
if (state.initDone == 0) {
    compbGetOutput(state.currTriggerLevel);
    state.initDone = 1;
}

// If the COMPB output is low...
if (state.currTriggerLevel == 0) {

    ... Do something here ...

    // Setup COMPB output high as next trigger
    evhSetupCompbTrigger(0, 1, EVH_COMPB_TRIG_ON_MATCH);
    state.currTriggerLevel = 1;

// Otherwise (the COMPB output is high)...
} else {

    ... Do something here ...

    // Setup COMPB output low as next trigger
    evhSetupCompbTrigger(0, 0, EVH_COMPB_TRIG_ON_MATCH);
    state.currTriggerLevel = 0;
}

Termination Code¶

// The currently enabled event trigger must be cancelled manually
evhCancelTrigger(0);

// Disable COMPB
compbDisable();

Procedures Overview¶

Name	Brief description
`evhCancelTrigger()`	Cancels a previous call to an event trigger setup procedure (for example `evhSetupGpioTrigger()` ) with matching event index, including any pending Event Handler Code execution if the trigger already has occurred. More …
`evhGetActiveTrigger()`	This procedure can be called from event handler code to determine which event index triggered the event handler code. More …
`evhSetupCompbTrigger()`	Sets up the COMPB output to trigger execution of the Event Handler Code . More …

Constants¶

Name	Description
`EVH_COMPB_TRIG_ON_EDGE`	COMPB trigger type: Generated on transition, edge from inverse level is required
`EVH_COMPB_TRIG_ON_MATCH`	COMPB trigger type: Generated on match, edge from inverse level is not required

Global Variables¶

None.

Procedures¶

evhCancelTrigger¶

Prototype: evhCancelTrigger(#evIndex)

Cancels a previous call to an event trigger setup procedure (for example evhSetupGpioTrigger() ) with matching event index, including any pending Event Handler Code execution if the trigger already has occurred.

This procedure should be called from the Termination Code if the task can be stopped by the application while an event trigger is enabled.

Parameter value(s)¶

#evIndex : Event index to be cancelled

evhGetActiveTrigger¶

Prototype: evhGetActiveTrigger(bvEvent)

This procedure can be called from event handler code to determine which event index triggered the event handler code.

Return value(s)¶

bvEvent : Bit-vector indicating the event index that triggered the event handler code

evhSetupCompbTrigger¶

Prototype: evhSetupCompbTrigger(#evIndex, #level, #type)

Sets up the COMPB output to trigger execution of the Event Handler Code . The trigger is one-shot.

The trigger occurs as soon as the COMPB output matches or transitions to the selected level. The Event Handler Code then starts when the Sensor Controller is idle or in standby.

Parameter value(s)¶

#evIndex : Event index to be triggered
#level : The COMPB output level that shall generate the trigger (1 = high level / rising edge, 0 = low level / falling edge)
#type : COMPB trigger type (EVH_COMPB_TRIG_ON_MATCH to trigger immediately on match, or EVH_COMPB_TRIG_ON_EDGE to wait for a transition to the level)