使用LPC812 SCT的state特性

小恩GG · 发表于 2020-1-6 09:28:49

Ø 问题

客户使用LPC812中的SCT模块想实现以下功能：

State 0 -> rising edges detected on input -> counter L started -> advance to state 1
State 1 -> Counter L reaches limit value -> output set high -> advance to state 2
State 2- > Falling edge on input -> output set low & counter reset -> set state to 0

复制代码

根据上述描述，可看出要实现的功能其实并不复杂，所以客户通过参考SDK软件库中multi_state_pwm工程较快的创建了如下工程代码：

/*
* Copyright (c) 2016, Freescale Semiconductor, Inc.
* Copyright 2016-2017 NXP
* All rights reserved.
*
* SPDX-License-Identifier: BSD-3-Clause
*
* Modified -- P0_13 now as input to counter to start it,
*
* State 0 -> rising edges detected on input -> counter L started -> advance to state 1
* State 1 -> Counter L reaches limit value -> output set high -> advance to state 2
* State 2- > Falling edge on input -> output set low & counter reset -> set state to 0
*/
#include "fsl_debug_console.h"
#include "board.h"
#include "fsl_sctimer.h"
#include "pin_mux.h"
/*******************************************************************************
* Definitions
******************************************************************************/
#define SCTIMER_CLK_FREQ CLOCK_GetFreq(kCLOCK_Irc)
#define DEMO_FIRST_SCTIMER_OUT kSCTIMER_Out_2
#define DEMO_SECOND_SCTIMER_OUT kSCTIMER_Out_3
/*******************************************************************************
* Prototypes
******************************************************************************/
/*******************************************************************************
* Code
******************************************************************************/
/*!
* @brief Main function
*/
int main(void)
{
sctimer_config_t sctimerInfo;
uint32_t riseEvent, fallEvent; // Modified
uint32_t stateNumber; // Modified
uint32_t eventCounterL;
uint32_t sctimerClock;
uint32_t matchValueL;
/* Board pin, clock, debug console init */
/* Enable clock of uart0. */
CLOCK_EnableClock(kCLOCK_Uart0);
/* Ser DIV of uart0. */
CLOCK_SetClkDivider(kCLOCK_DivUsartClk, 1U);
BOARD_InitPins();
BOARD_BootClockIRC12M();
BOARD_InitDebugConsole();
/* Enable clock of sct. */
CLOCK_EnableClock(kCLOCK_Sct);
sctimerClock = SCTIMER_CLK_FREQ;
/* Print a note to terminal */
// PRINTF("\r\nSCTimer example to use it in 16-bit mode\r\n");
// PRINTF("\r\nThe example shows both 16-bit counters running and toggling an output periodically ");
SCTIMER_GetDefaultConfig(&sctimerInfo);
/* Add judgment for change clock source*/
#if defined(SCTIMER_NEED_CHANGE_CLOCK_SOURCE)
sctimerInfo.clockMode = DEMO_CLOCK_MODE;
sctimerInfo.clockSelect = DEMO_CLOCK_SEL;
#endif
/* Switch to 16-bit mode */
sctimerInfo.enableCounterUnify = false;
/* Calculate prescaler and match value for Counter L for 10ms */
matchValueL = MSEC_TO_COUNT(100U, sctimerClock);
sctimerInfo.prescale_l = matchValueL / 65536;
matchValueL = matchValueL / (sctimerInfo.prescale_l + 1) - 1;
// Switch off synchronization for inputs to speed up TODO: Necessary??
// sctimerInfo.inputsync = 0x0U;
/* Initialize SCTimer module */
SCTIMER_Init(SCT0, &sctimerInfo);
stateNumber = SCTIMER_GetCurrentState(SCT0);
// STATE 0 /////////////////////////////////////////////////////////////////////////////////
// event 0
/* Schedule an event to look for a rising edge on input 1 in this state */
if (SCTIMER_CreateAndScheduleEvent(SCT0, kSCTIMER_InputRiseEvent, 0u, kSCTIMER_Input_1, kSCTIMER_Counter_L,
&riseEvent) == kStatus_Fail)
{
return -1;
}
/* Transition to next state when a rising edge is detected on input 1 */
SCTIMER_SetupNextStateAction(SCT0, stateNumber + 1, riseEvent);
// Goto next state
SCTIMER_IncreaseState(SCT0);
// STATE 1 /////////////////////////////////////////////////////////////////////////////////
// event 1
/* Schedule a single match event for Counter L */
if (SCTIMER_CreateAndScheduleEvent(SCT0, kSCTIMER_MatchEventOnly, matchValueL, 0, kSCTIMER_Counter_L,
&eventCounterL) == kStatus_Fail)
{
return -1;
}
// Set output in this state
SCTIMER_SetupOutputSetAction(SCT0, kSCTIMER_Out_0, eventCounterL);
/* Reset Counter L when Counter L event occurs TODO: Should counter be reset?? */
//SCTIMER_SetupCounterLimitAction(SCT0, kSCTIMER_Counter_L, eventCounterL);
/* Transition to next state when a rising edge detected on input 1 */
SCTIMER_SetupNextStateAction(SCT0, stateNumber + 2, eventCounterL);
// Goto next state
SCTIMER_IncreaseState(SCT0);
// STATE 2 /////////////////////////////////////////////////////////////////////////////////
// event 2
/* Schedule an event to look for a falling edge on input 1 in this state */
if (SCTIMER_CreateAndScheduleEvent(SCT0, kSCTIMER_InputFallEvent, 0u, kSCTIMER_Input_1, kSCTIMER_Counter_L,
&fallEvent) == kStatus_Fail)
{
return -1;
}
// Clear output when event occurs in this state
SCTIMER_SetupOutputClearAction(SCT0, kSCTIMER_Out_0, fallEvent);
// Transition to next state when event occurs in this state, i.e. loop back to initial state
SCTIMER_SetupNextStateAction(SCT0, 0u, fallEvent);
///////////////////////////////////////////////////////////////////////////////////////////
/* Start the L counter */
SCTIMER_StartTimer(SCT0, kSCTIMER_Counter_L);
while (1)
{
__asm("NOP"); /* delay */
}
}