ACMP - Analog Comparator#

Analog comparator (ACMP) Peripheral API.

The Analog Comparator is used to compare voltage of two analog inputs with a digital output indicating which input voltage is higher. Inputs can either be one of the selectable internal references or from external pins. Response time and current consumption can be configured by altering the current supply to the comparator.

ACMP is available down to EM3 and is able to wake up the system when input signals pass a certain threshold. Use ACMP_IntEnable() to enable an edge interrupt to use this functionality.

This example shows how to use the em_acmp.h API for comparing an input pin to an internal 2.5 V reference voltage.

/* The ACMP is a high-frequency peripheral so we need to enable
 * both the HFPER clock and the ACMP0 clock. */
CMU_ClockEnable(cmuClock_HFPER, true);
CMU_ClockEnable(cmuClock_ACMP0, true);

/* Initialize with default settings. */
ACMP_Init_TypeDef init = ACMP_INIT_DEFAULT;
init.enable = false;
ACMP_Init(ACMP0, &init);

/* Setup the two channels to compare. The first argument is the negative
 * channel and the second argument is the positive channel.
 *
 * Here we compare channel 0 with the 2.5 V internal reference. When
 * channel 0 is lower than 2.5 V then the ACMP output is 0 and when
 * channel 0 voltage is higher than 2.5 V then the ACMP output is 1. */
ACMP_ChannelSet(ACMP0, acmpChannel2V5, acmpChannel0);

/* To be able to probe the output we can send the ACMP output to a pin.
 * The second argument to this function is the pin location which is
 * device dependent. */
ACMP_GPIOSetup(ACMP0, 0, true, false);

/* Finally we enable the ACMP. */
ACMP_Enable(ACMP0);

Note

  • ACMP can also be used to compare two separate input pins.

ACMP also contains specialized hardware for capacitive sensing. This module contains the ACMP_CapsenseInit() function to initialize ACMP for capacitive sensing and the ACMP_CapsenseChannelSet() function to select the current capsense channel.

For applications that require capacitive sensing it is recommended to use a library, such as cslib, which is provided by Silicon Labs.

Modules#

ACMP_CapsenseInit_TypeDef

ACMP_Init_TypeDef

Enumerations#

enum
ACMP_CapsenseResistor_TypeDef {
acmpResistor0 = _ACMP_INPUTSEL_CSRESSEL_RES0
acmpResistor1 = _ACMP_INPUTSEL_CSRESSEL_RES1
acmpResistor2 = _ACMP_INPUTSEL_CSRESSEL_RES2
acmpResistor3 = _ACMP_INPUTSEL_CSRESSEL_RES3
}

Resistor values used for the internal capacitive sense resistor.

enum
ACMP_HysteresisLevel_TypeDef {
acmpHysteresisLevel0 = _ACMP_CTRL_HYSTSEL_HYST0
acmpHysteresisLevel1 = _ACMP_CTRL_HYSTSEL_HYST1
acmpHysteresisLevel2 = _ACMP_CTRL_HYSTSEL_HYST2
acmpHysteresisLevel3 = _ACMP_CTRL_HYSTSEL_HYST3
acmpHysteresisLevel4 = _ACMP_CTRL_HYSTSEL_HYST4
acmpHysteresisLevel5 = _ACMP_CTRL_HYSTSEL_HYST5
acmpHysteresisLevel6 = _ACMP_CTRL_HYSTSEL_HYST6
acmpHysteresisLevel7 = _ACMP_CTRL_HYSTSEL_HYST7
}

Hysteresis level.

enum
ACMP_WarmTime_TypeDef {
acmpWarmTime4 = _ACMP_CTRL_WARMTIME_4CYCLES
acmpWarmTime8 = _ACMP_CTRL_WARMTIME_8CYCLES
acmpWarmTime16 = _ACMP_CTRL_WARMTIME_16CYCLES
acmpWarmTime32 = _ACMP_CTRL_WARMTIME_32CYCLES
acmpWarmTime64 = _ACMP_CTRL_WARMTIME_64CYCLES
acmpWarmTime128 = _ACMP_CTRL_WARMTIME_128CYCLES
acmpWarmTime256 = _ACMP_CTRL_WARMTIME_256CYCLES
acmpWarmTime512 = _ACMP_CTRL_WARMTIME_512CYCLES
}

ACMP warmup time.

enum
ACMP_Channel_TypeDef {
acmpChannel0 = _ACMP_INPUTSEL_NEGSEL_CH0
acmpChannel1 = _ACMP_INPUTSEL_NEGSEL_CH1
acmpChannel2 = _ACMP_INPUTSEL_NEGSEL_CH2
acmpChannel3 = _ACMP_INPUTSEL_NEGSEL_CH3
acmpChannel4 = _ACMP_INPUTSEL_NEGSEL_CH4
acmpChannel5 = _ACMP_INPUTSEL_NEGSEL_CH5
acmpChannel6 = _ACMP_INPUTSEL_NEGSEL_CH6
acmpChannel7 = _ACMP_INPUTSEL_NEGSEL_CH7
acmpChannel1V25 = _ACMP_INPUTSEL_NEGSEL_1V25
acmpChannel2V5 = _ACMP_INPUTSEL_NEGSEL_2V5
acmpChannelVDD = _ACMP_INPUTSEL_NEGSEL_VDD
acmpChannelCapSense = _ACMP_INPUTSEL_NEGSEL_CAPSENSE
}

ACMP inputs.

Functions#

void
ACMP_CapsenseInit(ACMP_TypeDef *acmp, const ACMP_CapsenseInit_TypeDef *init)

Set up ACMP for use in capacitive sense applications.

void
ACMP_CapsenseChannelSet(ACMP_TypeDef *acmp, ACMP_Channel_TypeDef channel)

Set the ACMP channel used for capacitive sensing.

void
ACMP_ChannelSet(ACMP_TypeDef *acmp, ACMP_Channel_TypeDef negSel, ACMP_Channel_TypeDef posSel)

Set which channels should be used in ACMP comparisons.

void
ACMP_Disable(ACMP_TypeDef *acmp)

Disable ACMP.

void
ACMP_Enable(ACMP_TypeDef *acmp)

Enable ACMP.

void
ACMP_GPIOSetup(ACMP_TypeDef *acmp, uint32_t location, bool enable, bool invert)

Set up GPIO output from ACMP.

void
ACMP_Init(ACMP_TypeDef *acmp, const ACMP_Init_TypeDef *init)

Initialize ACMP.

void
ACMP_Reset(ACMP_TypeDef *acmp)

Reset ACMP to the same state that it was in after a hardware reset.

void
ACMP_IntClear(ACMP_TypeDef *acmp, uint32_t flags)

Clear one or more pending ACMP interrupts.

void
ACMP_IntDisable(ACMP_TypeDef *acmp, uint32_t flags)

Disable one or more ACMP interrupts.

void
ACMP_IntEnable(ACMP_TypeDef *acmp, uint32_t flags)

Enable one or more ACMP interrupts.

uint32_t
ACMP_IntGet(ACMP_TypeDef *acmp)

Get pending ACMP interrupt flags.

uint32_t
ACMP_IntGetEnabled(ACMP_TypeDef *acmp)

Get enabled and pending ACMP interrupt flags.

void
ACMP_IntSet(ACMP_TypeDef *acmp, uint32_t flags)

Set one or more pending ACMP interrupts from software.

Macros#

#define
ACMP_CAPSENSE_INIT_DEFAULT undefined

A default configuration for capacitive sense mode initialization.

#define
ACMP_INIT_DEFAULT undefined

Default configuration for ACMP regular initialization.

Enumeration Documentation#

ACMP_CapsenseResistor_TypeDef#

ACMP_CapsenseResistor_TypeDef

Resistor values used for the internal capacitive sense resistor.

See data sheet for your device for details on each resistor value.

Enumerator
acmpResistor0

Resistor value 0.

acmpResistor1

Resistor value 1.

acmpResistor2

Resistor value 2.

acmpResistor3

Resistor value 3.


Definition at line 57 of file platform/emlib/inc/em_acmp.h

ACMP_HysteresisLevel_TypeDef#

ACMP_HysteresisLevel_TypeDef

Hysteresis level.

See data sheet for your device for details on each level.

Enumerator
acmpHysteresisLevel0

Hysteresis level 0.

acmpHysteresisLevel1

Hysteresis level 1.

acmpHysteresisLevel2

Hysteresis level 2.

acmpHysteresisLevel3

Hysteresis level 3.

acmpHysteresisLevel4

Hysteresis level 4.

acmpHysteresisLevel5

Hysteresis level 5.

acmpHysteresisLevel6

Hysteresis level 6.

acmpHysteresisLevel7

Hysteresis level 7.


Definition at line 82 of file platform/emlib/inc/em_acmp.h

ACMP_WarmTime_TypeDef#

ACMP_WarmTime_TypeDef

ACMP warmup time.

The delay is measured in HFPERCLK / HFPERCCLK cycles and should be at least 10 us.

Enumerator
acmpWarmTime4

4 cycles warmup

acmpWarmTime8

8 cycles warmup

acmpWarmTime16

16 cycles warmup

acmpWarmTime32

32 cycles warmup

acmpWarmTime64

64 cycles warmup

acmpWarmTime128

128 cycles warmup

acmpWarmTime256

256 cycles warmup

acmpWarmTime512

512 cycles warmup


Definition at line 128 of file platform/emlib/inc/em_acmp.h

ACMP_Channel_TypeDef#

ACMP_Channel_TypeDef

ACMP inputs.

Note that scaled VDD and bandgap references can only be used as negative inputs.

Enumerator
acmpChannel0

Channel 0.

acmpChannel1

Channel 1.

acmpChannel2

Channel 2.

acmpChannel3

Channel 3.

acmpChannel4

Channel 4.

acmpChannel5

Channel 5.

acmpChannel6

Channel 6.

acmpChannel7

Channel 7.

acmpChannel1V25

1.25 V internal reference

acmpChannel2V5

2.5 V internal reference

acmpChannelVDD

Scaled VDD reference.

acmpChannelCapSense

Capacitive sense mode.


Definition at line 540 of file platform/emlib/inc/em_acmp.h

Function Documentation#

ACMP_CapsenseInit#

void ACMP_CapsenseInit (ACMP_TypeDef * acmp, const ACMP_CapsenseInit_TypeDef * init)

Set up ACMP for use in capacitive sense applications.

Parameters
[in]acmp

A pointer to the ACMP peripheral register block.

[in]init

A pointer to the initialization structure used to configure ACMP for capacitive sensing operation.

This function sets up ACMP for use in capacitive sense applications. To use the capacitive sense functionality in the ACMP, use the PRS output of the ACMP module to count the number of oscillations in the capacitive sense circuit (possibly using a TIMER).

Note

  • A basic example of capacitive sensing can be found in the STK BSP (capsense demo).


Definition at line 166 of file platform/emlib/src/em_acmp.c

ACMP_CapsenseChannelSet#

void ACMP_CapsenseChannelSet (ACMP_TypeDef * acmp, ACMP_Channel_TypeDef channel)

Set the ACMP channel used for capacitive sensing.

Parameters
[in]acmp

A pointer to the ACMP peripheral register block.

[in]channel

The ACMP channel to use for capacitive sensing (Possel).

Note

  • A basic example of capacitive sensing can be found in the STK BSP (capsense demo).


Definition at line 248 of file platform/emlib/src/em_acmp.c

ACMP_ChannelSet#

void ACMP_ChannelSet (ACMP_TypeDef * acmp, ACMP_Channel_TypeDef negSel, ACMP_Channel_TypeDef posSel)

Set which channels should be used in ACMP comparisons.

Parameters
[in]acmp

A pointer to the ACMP peripheral register block.

N/AnegSel

A channel to use on the negative input to the ACMP.

N/AposSel

A channel to use on the positive input to the ACMP.


Definition at line 507 of file platform/emlib/src/em_acmp.c

ACMP_Disable#

void ACMP_Disable (ACMP_TypeDef * acmp)

Disable ACMP.

Parameters
[in]acmp

A pointer to the ACMP peripheral register block.


Definition at line 286 of file platform/emlib/src/em_acmp.c

ACMP_Enable#

void ACMP_Enable (ACMP_TypeDef * acmp)

Enable ACMP.

Parameters
[in]acmp

A pointer to the ACMP peripheral register block.


Definition at line 315 of file platform/emlib/src/em_acmp.c

ACMP_GPIOSetup#

void ACMP_GPIOSetup (ACMP_TypeDef * acmp, uint32_t location, bool enable, bool invert)

Set up GPIO output from ACMP.

Parameters
[in]acmp

A pointer to the ACMP peripheral register block.

N/Alocation

The pin location to use. See the data sheet for location to pin mappings.

N/Aenable

Enable or disable pin output.

N/Ainvert

Invert output.

Note

  • GPIO must be enabled in the CMU before this function call, i.e., 

    CMU_ClockEnable(cmuClock_GPIO, true);

Definition at line 462 of file platform/emlib/src/em_acmp.c

ACMP_Init#

void ACMP_Init (ACMP_TypeDef * acmp, const ACMP_Init_TypeDef * init)

Initialize ACMP.

Parameters
[in]acmp

A pointer to the ACMP peripheral register block.

[in]init

A pointer to the initialization structure used to configure ACMP.


Definition at line 580 of file platform/emlib/src/em_acmp.c

ACMP_Reset#

void ACMP_Reset (ACMP_TypeDef * acmp)

Reset ACMP to the same state that it was in after a hardware reset.

Parameters
[in]acmp

A pointer to the ACMP peripheral register block.

Note

  • The GPIO ACMP ROUTE register is NOT reset by this function to allow for centralized setup of this feature.

  • The peripheral may be enabled and disabled during reset.


Definition at line 367 of file platform/emlib/src/em_acmp.c

ACMP_IntClear#

void ACMP_IntClear (ACMP_TypeDef * acmp, uint32_t flags)

Clear one or more pending ACMP interrupts.

Parameters
[in]acmp

A pointer to the ACMP peripheral register block.

[in]flags

Pending ACMP interrupt source to clear. Use a bitwise logic OR combination of valid interrupt flags for the ACMP module. The flags can be, for instance, ACMP_IFC_EDGE or ACMP_IFC_WARMUP.


Definition at line 989 of file platform/emlib/inc/em_acmp.h

ACMP_IntDisable#

void ACMP_IntDisable (ACMP_TypeDef * acmp, uint32_t flags)

Disable one or more ACMP interrupts.

Parameters
[in]acmp

A pointer to the ACMP peripheral register block.

[in]flags

ACMP interrupt sources to disable. Use a bitwise logic OR combination of valid interrupt flags for the ACMP module. The flags can be, for instance, ACMP_IEN_EDGE or ACMP_IEN_WARMUP.


Definition at line 1010 of file platform/emlib/inc/em_acmp.h

ACMP_IntEnable#

void ACMP_IntEnable (ACMP_TypeDef * acmp, uint32_t flags)

Enable one or more ACMP interrupts.

Parameters
[in]acmp

A pointer to the ACMP peripheral register block.

[in]flags

ACMP interrupt sources to enable. Use a bitwise logic OR combination of valid interrupt flags for the ACMP module. The flags can be, for instance, ACMP_IEN_EDGE or ACMP_IEN_WARMUP.

Note

  • Depending on the use, a pending interrupt may already be set prior to enabling the interrupt. Consider using ACMP_IntClear() prior to enabling if a pending interrupt should be ignored.


Definition at line 1032 of file platform/emlib/inc/em_acmp.h

ACMP_IntGet#

uint32_t ACMP_IntGet (ACMP_TypeDef * acmp)

Get pending ACMP interrupt flags.

Parameters
[in]acmp

A pointer to the ACMP peripheral register block.

Note

  • This function does not clear event bits.

Returns

  • Pending ACMP interrupt sources. A bitwise logic OR combination of valid interrupt flags for the ACMP module. The pending interrupt sources can be, for instance, ACMP_IF_EDGE or ACMP_IF_WARMUP.


Definition at line 1056 of file platform/emlib/inc/em_acmp.h

ACMP_IntGetEnabled#

uint32_t ACMP_IntGetEnabled (ACMP_TypeDef * acmp)

Get enabled and pending ACMP interrupt flags.

Parameters
[in]acmp

A pointer to the ACMP peripheral register block.

Useful for handling more interrupt sources in the same interrupt handler.

Note

  • This function does not clear interrupt flags.

Returns

  • Pending and enabled ACMP interrupt sources. The return value is the bitwise AND combination of

    • the OR combination of enabled interrupt sources in ACMPx_IEN_nnn register (ACMPx_IEN_nnn) and

    • the OR combination of valid interrupt flags of the ACMP module (ACMPx_IF_nnn).


Definition at line 1080 of file platform/emlib/inc/em_acmp.h

ACMP_IntSet#

void ACMP_IntSet (ACMP_TypeDef * acmp, uint32_t flags)

Set one or more pending ACMP interrupts from software.

Parameters
[in]acmp

A pointer to the ACMP peripheral register block.

[in]flags

ACMP interrupt sources to set as pending. Use a bitwise logic OR combination of valid interrupt flags for the ACMP module. The flags can be, for instance, ACMP_IFS_EDGE or ACMP_IFS_WARMUP.


Definition at line 1104 of file platform/emlib/inc/em_acmp.h

Macro Definition Documentation#

ACMP_CAPSENSE_INIT_DEFAULT#

#define ACMP_CAPSENSE_INIT_DEFAULT
Value:
{ \
false, /* fullBias */ \
false, /* halfBias */ \
0x7, /* biasProg */ \
acmpWarmTime512, /* 512 cycle warmup to be safe */ \
acmpHysteresisLevel5, \
acmpResistor3, \
false, /* low power reference */ \
0x3D, /* VDD level */ \
true /* Enable after init. */ \
}

A default configuration for capacitive sense mode initialization.


Definition at line 718 of file platform/emlib/inc/em_acmp.h

ACMP_INIT_DEFAULT#

#define ACMP_INIT_DEFAULT
Value:
{ \
false, /* fullBias */ \
false, /* halfBias */ \
0x7, /* biasProg */ \
false, /* No interrupt on falling edge. */ \
false, /* No interrupt on rising edge. */ \
acmpWarmTime512, /* 512 cycle warmup to be safe */ \
acmpHysteresisLevel5, \
false, /* Disabled emitting inactive value during warmup. */ \
false, /* low power reference */ \
0x3D, /* VDD level */ \
true /* Enable after init. */ \
}

Default configuration for ACMP regular initialization.


Definition at line 867 of file platform/emlib/inc/em_acmp.h