ARM Cordio WSF（三）——WSF在nRF52840平台移植

前文介绍了WSF架构及其WSF API，本文将介绍如何在一个硬件平台上使用WSF，这里基于stack项目下的nRF52840平台进行介绍。

3、PAL实现

对于要在一个处理器上运行WSF（逻辑情况），需要处理系统的调度、系统SysTick、中断上下文（Critical Section）、平台定时器相关，主要涉及内容如下：

timer移植，这里在平台相关的文件：pal_timer.c/h中实现；
中断，Critical Section相关处理，避免中断执行上下文的破坏，平台相关文件：pal_sys.c/h;
若需要使用NVM，则需要pal_flash.h/c；
对于wsf_heap相关操作，必要也需要在pal_sys.c/h中进行适配。

在WSF的架构中，均以PAL_*的形式来定义，即以平台抽象层（PAL，Platform Abstraction Layer）形式实现。

3.1 pal_sys

对于系统相关的PAL实现，关键接口如下（pal_sys.h）：

/* Initialization */
void PalSysInit(void);/* Diagnostics */
void PalSysAssertTrap(void);
void PalSysSetTrap(bool_t enable);
uint32_t PalSysGetAssertCount(void);
uint32_t PalSysGetStackUsage(void);/* Power Management */
void PalSysSleep(void);  //休眠相关处理
bool_t PalSysIsBusy(void);
void PalSysSetBusy(void);
void PalSysSetIdle(void);/* Critical Section */
void PalEnterCs(void);
void PalExitCs(void);

包括系统初始、诊断相关、功耗管理相关、以及Critical Section的处理。

/*! \brief      Free memory for pool buffers (align to word boundary). */
uint32_t palSysFreeMem[FREE_MEM_SIZE/sizeof(uint32_t)];uint8_t *SystemHeapStart = (uint8_t *) palSysFreeMem;
uint32_t SystemHeapSize = FREE_MEM_SIZE;

关于Critical Section的处理，主要为中断的开启与关闭：

void PalEnterCs(void)
{#ifdef __IAR_SYSTEMS_ICC____disable_interrupt();#endif#ifdef __GNUC____asm volatile ("cpsid i");#endif#ifdef __CC_ARM__disable_irq();#endif
}

void PalSysInit(void)
{/* Enable Flash cache */NRF_NVMC->ICACHECNF |= (NVMC_ICACHECNF_CACHEEN_Enabled << NVMC_ICACHECNF_CACHEEN_Pos);/* Use 16 MHz crystal oscillator (system starts up using 16MHz RC oscillator). */NRF_CLOCK->EVENTS_HFCLKSTARTED = 0;NRF_CLOCK->TASKS_HFCLKSTART    = 1;while (NRF_CLOCK->EVENTS_HFCLKSTARTED == 0) { }palSysAssertCount = 0;PalSysAssertTrapEnable = TRUE;palSysBusyCount = 0;PalRtcInit();
}

在平台初始化函数中，完成RTC初始化、系统相关设置，配置时钟等操作。

3.2 pal_timer

在platform/pal_timer.c中，实现定时器驱动程序，用于调度程序和其他低功耗相关任务。其在实现时依赖于pal_rtc.c和一些调度程序以及nRF528**基带相关API。

对于一个调度定时器而言，通常需要实现以下相关接口（pal_timer.h）：

/* Initialization */
void PalTimerInit(PalTimerCompCback_t expCback);
void PalTimerDeInit(void);/* Control and Status */
PalTimerState_t PalTimerGetState(void);
void PalTimerStart(uint32_t expUsec);
void PalTimerStop(void);
uint32_t PalTimerGetCurrentTime(void);

以下为在NRF处理器上实现调度定时器，包括控制块、调度定时器初始化等。

/*! \brief      Scheduler timer driver control block. */
static struct
{PalTimerState_t    state;            /*!< State. */uint32_t           compareVal;       /*!<  Absolute compare value for timer expiry interrupt. */PalTimerCompCback_t expCback;         /*!< Timer expiry call back function. */
} palTimerCb;

调度定时器初始化：

void PalTimerInit(PalTimerCompCback_t expCback)
{#if SCH_TIMER_REQUIRED == TRUE#if BB_CLK_RATE_HZ == 32768PalRtcIrqRegister(RTC_CHANNEL_START_BB, palTimerRtcIrqHandler);#else/* Give scheduler timer the highest priority. */NVIC_SetPriority(TIMER1_IRQn, 0);  /* highest priority */NVIC_DisableIRQ(TIMER1_IRQn);/* stop timer if it was somehow running (timer must be stopped for configuration) */NRF_TIMER1->TASKS_STOP  = 1;/* clear timer to zero count */NRF_TIMER1->TASKS_CLEAR = 1;/* configure timer */NRF_TIMER1->MODE      = TIMER_MODE_MODE_Timer;NRF_TIMER1->BITMODE   = TIMER_BITMODE_BITMODE_32Bit;NRF_TIMER1->PRESCALER = PAL_TIMER_1MHZ_PRESCALER;  /* f = 16MHz / (2 ^ TIMER_PRESCALER) *//* timer1 is a free running clock. */NRF_TIMER1->TASKS_START = 1;/* Clear out and enable timer1 interrupt at system level. */NRF_TIMER1->INTENCLR = 0xFFFFFFFF;NRF_TIMER1->EVENTS_COMPARE[TIMER_CHANNEL_START_BB] = 0;NVIC_ClearPendingIRQ(TIMER1_IRQn);NVIC_EnableIRQ(TIMER1_IRQn);#endif#endifpalTimerCb.compareVal = 0;palTimerCb.expCback = expCback;palTimerCb.state = PAL_TIMER_STATE_READY;
}

调度定时器的源根据宏定义，可以设置两种：一种是RTC 32.768kHz的源；另一种是基于定时器Timer1来实现。

通过void PalTimerStart(uint32_t expTimeUsec)与void PalTimerStop()来实现定时器的开启与停止。

相应的，根据设置情况，需要在palTimerRtcIrqHandler或TIMER1_IRQn中断中处理定时器相关。

void TIMER1_IRQHandler(void)
{/* Callback function could restart timer1. However, we blindly stop timer1 first. */NRF_TIMER1->INTENCLR = TIMER_INTENCLR_COMPARE0_Msk;/* Clear event again just in case. */NRF_TIMER1->EVENTS_COMPARE[TIMER_CHANNEL_START_BB] = 0;palTimerCb.state = PAL_TIMER_STATE_READY;if (palTimerCb.expCback)  //初始化中设定的定时器回调函数{palTimerCb.expCback();  }
}

3.3 pal_flash

对于平台上Flash相关操作，提供NVM的使用，通过pal_flash.h来实现。

/* Initialization */
void PalFlashInit(PalFlashCback_t actCback);
void PalFlashDeInit(void);/* Control and Status */
PalFlashState_t PalNvmGetState(void);
uint32_t PalNvmGetTotalSize(void);
uint32_t PalNvmGetSectorSize(void);/* Data Transfer */
void PalFlashRead(void *pBuf, uint32_t size, uint32_t srcAddr);
void PalFlashWrite(void *pBuf, uint32_t size, uint32_t dstAddr);
void PalFlashEraseSector(uint32_t size, uint32_t startAddr);
void PalFlashEraseChip(void);

以nRF52840为例，为QSPI Flash，其实现上，通过完成对底层驱动的初始化，进而可实现对Flash的访问。

void PalFlashInit(PalFlashCback_t actCback)
{uint32_t status;uint8_t  temp = 0x40;(void)actCback;nrfx_qspi_config_t config ={                                                                       \.xip_offset  = NRFX_QSPI_CONFIG_XIP_OFFSET,                         \.pins = {                                                           \.sck_pin     = BSP_QSPI_SCK_PIN,                                 \.csn_pin     = BSP_QSPI_CSN_PIN,                                 \.io0_pin     = BSP_QSPI_IO0_PIN,                                 \.io1_pin     = BSP_QSPI_IO1_PIN,                                 \.io2_pin     = BSP_QSPI_IO2_PIN,                                 \.io3_pin     = BSP_QSPI_IO3_PIN,                                 \},                                                                  \.irq_priority   = (uint8_t)NRFX_QSPI_CONFIG_IRQ_PRIORITY,           \.prot_if = {                                                        \.readoc     = (nrf_qspi_readoc_t)NRFX_QSPI_CONFIG_READOC,       \.writeoc    = (nrf_qspi_writeoc_t)NRFX_QSPI_CONFIG_WRITEOC,     \.addrmode   = (nrf_qspi_addrmode_t)NRFX_QSPI_CONFIG_ADDRMODE,   \.dpmconfig  = false,                                            \},                                                                  \.phy_if = {                                                         \.sck_freq   = (nrf_qspi_frequency_t)NRFX_QSPI_CONFIG_FREQUENCY, \.sck_delay  = (uint8_t)NRFX_QSPI_CONFIG_SCK_DELAY,              \.spi_mode   = (nrf_qspi_spi_mode_t)NRFX_QSPI_CONFIG_MODE,       \.dpmen      = false                                             \},                                                                  \};/* Verify palFlashCacheBuf size is at least 2. */PAL_FLASH_PARAM_CHECK(PAL_FLASH_CACHE_BUF_SIZE >= 2);status = nrfx_qspi_init(&config, NULL, NULL);PAL_FLASH_PARAM_CHECK(status == NRFX_SUCCESS);nrf_qspi_cinstr_conf_t cinstr_cfg = {.opcode    = QSPI_STD_CMD_RSTEN,.length    = NRF_QSPI_CINSTR_LEN_1B,.io2_level = 1,.io3_level = 1,.wipwait   = 1,.wren      = 1};/* Send reset enable. */status = nrfx_qspi_cinstr_xfer(&cinstr_cfg, NULL, NULL);/* Send reset command */cinstr_cfg.opcode = QSPI_STD_CMD_RST;status = nrfx_qspi_cinstr_xfer(&cinstr_cfg, NULL, NULL);PAL_FLASH_PARAM_CHECK(status == NRFX_SUCCESS);/* Switch to qspi mode */cinstr_cfg.opcode = QSPI_STD_CMD_WRSR;cinstr_cfg.length = NRF_QSPI_CINSTR_LEN_2B;status = nrfx_qspi_cinstr_xfer(&cinstr_cfg, &temp, NULL);PAL_FLASH_PARAM_CHECK(status == NRFX_SUCCESS);memset(&palFlashCb, 0, sizeof(palFlashCb));palFlashCb.state = PAL_FLASH_STATE_READY;(void)status;}

对于Flash的读与写实现：

void PalFlashRead(void *pBuf, uint32_t size, uint32_t srcAddr)
{uint32_t readSize = PAL_FLASH_WORD_ALIGN(size);uint32_t actualSize = size;uint32_t status;uint16_t addrOffset = 0;do{if (readSize <= sizeof(palFlashCacheBuf)){/* Read data. */status = nrfx_qspi_read(palFlashCacheBuf, readSize, srcAddr + addrOffset);memcpy((uint8_t*)pBuf + addrOffset, palFlashCacheBuf, actualSize);readSize = 0;}else{/* Read data. */status = nrfx_qspi_read(palFlashCacheBuf, sizeof(palFlashCacheBuf), srcAddr + addrOffset);memcpy((uint8_t*)pBuf + addrOffset, palFlashCacheBuf, sizeof(palFlashCacheBuf));addrOffset += sizeof(palFlashCacheBuf);readSize -= sizeof(palFlashCacheBuf);actualSize -= sizeof(palFlashCacheBuf);}} while (readSize != 0);(void)status;
}

void PalFlashWrite(void *pBuf, uint32_t size, uint32_t dstAddr)
{uint32_t writeSize = PAL_FLASH_WORD_ALIGN(size);uint32_t actualSize = size;uint32_t status;uint16_t addrOffset = 0;do{if (writeSize <= sizeof(palFlashCacheBuf)){memcpy(palFlashCacheBuf, (uint8_t*)pBuf + addrOffset, actualSize);memset((uint8_t*)palFlashCacheBuf + actualSize, 0xFF, sizeof(palFlashCacheBuf) - actualSize);/* Write data. */status = nrfx_qspi_write(palFlashCacheBuf, writeSize, dstAddr + addrOffset);writeSize = 0;}else{memcpy(palFlashCacheBuf, (uint8_t*)pBuf + addrOffset, sizeof(palFlashCacheBuf));/* Write data. */status = nrfx_qspi_write(palFlashCacheBuf, sizeof(palFlashCacheBuf), dstAddr + addrOffset);addrOffset += sizeof(palFlashCacheBuf);writeSize -= sizeof(palFlashCacheBuf);actualSize -= sizeof(palFlashCacheBuf);}} while (writeSize != 0);(void)status;
}

3.4 SysTick实现

对于Cortex-M系列的处理器，都可以使用SysTick_Handler来实现系统的tick，这样更具有移植性。
对于SysTick_Handler的处理，
1）关键管理一个系统的tick，这里的示例使用32bit全局变量来实现；
2）调用WSF中的Timer来更新Tick，对于设置的wsf_timer，超时的，将触发定时器任务，进而触发相应的事件。

//由于在中断上下文处理，使用volatile关键字
volatile uint32_t g_sys_tick_count = 0;void SysTick_Handler(void)  
{g_sys_tick_count++;WsfTimerUpdateTicks();
}

关于SysTick时钟的设备，则，根据系统期望的tick情况（如10ms）来设置。

    /* Configure SysTick to generate an interrupt every millisecond */SysTick_Config(WSF_MS_PER_TICK * GetSystemCoreClock() / 1000);

其中，GetSystemCoreClock获取系统时钟情况，不同平台根据设置的系统时钟来设置。

基本调用逻辑与思路如下图所示：
在这里插入图片描述
在WsfTimerUpdate中，将已经超时的Task设置定时器事件。

/* timer expired; set task for this timer as ready */
WsfTaskSetReady(pElem->handlerId, WSF_TIMER_EVENT);void WsfTaskSetReady(wsfHandlerId_t handlerId, wsfTaskEvent_t event)
{/* Unused parameter */(void)handlerId;WSF_CS_INIT(cs);uint32_t lock = WSF_CS_ENTER();wsfOs.task.taskEventMask |= event;WSF_CS_EXIT(lock);/* set event in OS */
}

最终，在wsfOsDispatcher中调用。

    /*--- Start OS Dispatcher in a loop ---*/while(1){wsfOsDispatcher();}

持续更新，系列文章，收藏关注吧！

1、ARM Cordio WSF（一）——架构介绍
2、ARM Cordio WSF（二）——API接口介绍