The input capture unit

The input capture unit actor can be used to analyze digital signals and waveforms. It can be used in two modes: Edge counting and time measurement.

The input capture unit can measure signals with an average frequency below 1 MHz (the total time for 100 consecutive edges must be >= 50 uS).

Protocols and actors

Currently one input capture actor is supported: minihil.platform.adapters.inputCapture.AInputCaptureUnit.

The actors function port supports the following messages

Table 1. Incoming Messages
Message Type Description

startEdgeCounting

void

Start counting edges only. Measured durations are discarded

stopEdgeCounting

void

stop edge counting and request results

startMeasurement

DInputCaptureMeasurementConfig

start a precise edge time measurement. The passed output buffer must have enough space for all expected edges

stopMeasurement

void

stop the measurement and request results
Table 2. Outgoing Messages
Message Type Description

measurementStarted

void

positive reply to startEdgeCounting and startMeasurement if the measurement/counting was started successfully

measurementAlreadyRunning

void

reply if a measurement/counting is running when a startMeasurement or startEdgeCounting message is received

noActiveMeasurement

void

reply if stopMeasurement or stopEdgeCounting are received while no measurement/counting was active

measurementStopped

DInputCaptureMeasurementResult

Reply to stopMeasurement

edgeCountStopped

DEdgeCountResult

Reply to stopEdgeCounting

bufferOverflow

void

Output buffer overflow. Measurement aborted

internalBufferOverflow

void

Internal buffer overflow. Measurement aborted

Actor documentation

This actor uses a timer + dma to measure the time passed during edges on the input pin.

Have a look at the fct ports protocol (PInputCaptureUnitCtrl) for usage details

The maximum input frequency should be < 1 MHz to avoid buffer overflows

Input: PA0

Used resources: DMA2_Stream4 TIM2

Structure

Table 3. Ports
Name Protocol Type Kind Multiplicity Description

triggerAnalysisEvt

PInterrupt

conjugated

internal

1

internalCfg

PInputCaptureInternalCfg

conjugated

internal

1

fct

PInputCaptureUnitCtrl

regular

relay

1

Behavior

State Machine
Top Level State
done

(no description)

Edge counting mode

Edge counting can be started when no other measurement is currently active. To start counting edges send a startEdgeCounting() message. The edge counting measurement is only started if the reply is a measurementStarted() message. If any other message is replied no measurement has been started.

A total edge count (split by rising and falling edges) is returned after a stopEdgeCounting() is received.

During edge counting mode no external buffers are used. The maximum number of edges counted is limited by uint32 max (for falling and rising edges each). If no edge is detected for more than 2100 seconds an internal timeout buffer will overflow and the measurement will be aborted.

Time measurement mode

Waveform time measurement can be started when no other measurement is currently active. To start a measurement send a startMeasurement(DInputCaptureMeasurementConfig) message. The measurement is only started if the reply is a measurementStarted() message.

An output buffer with elements of type EdgeTime must be provided in the passed measurement config (DInputCaptureMeasurementConfig). The EdgeTime type is defined in minihil/InputCapture.h in the SimModelLib.

Data class to configure an edge time measurement

Table 4. Attributes
Name Type Description

outputBuffer

EdgeTime

The output buffer in which the timing data are to be saved. Elements should be of type EdgeTime. E.g. EdgeTime outBuffer[500];

bufferLen_entries should be the number of entries in the output buffer. E.g. sizeof(outputBuffer)/sizeof(EdgeTime)

bufferLen_entries

uint32

CaGe example: Time measurement mode

targetcode:
	``
		#include "minihil/InputCapture.h"
		// includes or defines
		static EdgeTime icuOutputBuffer[800];
	``
;

// NOTE: The icu port is of type conjugated PInputCaptureUnitCtrl

Step testWaveform:
	timeout ... s
	action
		``
			DInputCaptureMeasurementConfig cfg;
			cfg.outputBuffer = icuOutputBuffer;
			cfg.bufferLen_entries = sizeof(icuOutputBuffer) / sizeof(icuOutputBuffer[0]);
		``
		icu.startMeasurement(``&cfg``)
	reaction
		expect icu.measurementStarted
	action
		// trigger your waveform
    reaction
        // .. wait for your wave form to end
	action
		icu.stopMeasurement
	reaction
		icu.measurementStopped => [data |
			expect ``data.risingEdgesCount`` == 2
			expect ``data.fallingEdgesCount`` == 2
			expect ``data.outputBuffer[0].type == EdgeType_RISING``
			expect ``data.outputBuffer[1].type == EdgeType_FALLING``
			expect ``data.outputBuffer[2].type == EdgeType_RISING``
			expect ``data.outputBuffer[3].type == EdgeType_FALLING``
			expect ``data.outputBuffer[1].timeOffset`` in range [0.002..0.003] // first falling edge
			expect ``data.outputBuffer[2].timeOffset`` in range [0.003..0.004] // second rising edge
			expect ``data.outputBuffer[3].timeOffset`` in range [0.008..0.009] // second falling edge
		]
;