如何使用本期板卡实现音频播放器

Funpack11期于10月31日截止后，到现在已审核完毕，相信审核通过的小伙伴都已经收到祝贺邮件了，那就静等返款吧。

本期的任务也是很有用意思，四选一，难度中等。这款来自NXP的强大的LPC55S69-EVK在群友们和各种开源资料的帮助下被大家玩的非常深入，轻松完成这期的几个任务。

下面就来看看vic网友如何使用本期板卡实现音频播放器的吧。以下项目已开源在电子森林：https://www.eetree.cn/project/detail/626，大家感兴趣的可以来一起学习。

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1. 实现功能说明本次使用LCP55S69-EVK开发板显示的功能是，任务一：读取SD卡中的音频文件，使用板卡上的3.5mm音频接口播放音乐。2. 功能代码展示2.1. 主函数在主函数中主要是对需要用到的外设进行初始化，例如：USART、I2C、I2S、Codec等，最后创两个任务分别用于完成SD卡管理以及通过USART0提供shell接口。

int main(void){    int ret;
    /* set BOD VBAT level to 1.65V */    POWER_SetBodVbatLevel(kPOWER_BodVbatLevel1650mv, kPOWER_BodHystLevel50mv, false);    CLOCK_EnableClock(kCLOCK_InputMux);    CLOCK_EnableClock(kCLOCK_Iocon);    CLOCK_EnableClock(kCLOCK_Gpio0);    CLOCK_EnableClock(kCLOCK_Gpio1);
    /* USART0 clock */    CLOCK_AttachClk(BOARD_DEBUG_UART_CLK_ATTACH);
    /* I2C clock */    CLOCK_AttachClk(kFRO12M_to_FLEXCOMM4);
    PMC->PDRUNCFGCLR0 |= PMC_PDRUNCFG0_PDEN_XTAL32M_MASK;   /*!< Ensure XTAL16M is on  */    PMC->PDRUNCFGCLR0 |= PMC_PDRUNCFG0_PDEN_LDOXO32M_MASK;  /*!< Ensure XTAL16M is on  */    SYSCON->CLOCK_CTRL |= SYSCON_CLOCK_CTRL_CLKIN_ENA_MASK; /*!< Ensure CLK_IN is on  */    ANACTRL->XO32M_CTRL |= ANACTRL_XO32M_CTRL_ENABLE_SYSTEM_CLK_OUT_MASK;
    /*!< Switch PLL0 clock source selector to XTAL16M */    CLOCK_AttachClk(kEXT_CLK_to_PLL0);
    const pll_setup_t pll0Setup = {        .pllctrl = SYSCON_PLL0CTRL_CLKEN_MASK | SYSCON_PLL0CTRL_SELI(2U) | SYSCON_PLL0CTRL_SELP(31U),        .pllndec = SYSCON_PLL0NDEC_NDIV(125U),        .pllpdec = SYSCON_PLL0PDEC_PDIV(8U),        .pllsscg = {0x0U, (SYSCON_PLL0SSCG1_MDIV_EXT(3072U) | SYSCON_PLL0SSCG1_SEL_EXT_MASK)},        .pllRate = 24576000U,        .flags   = PLL_SETUPFLAG_WAITLOCK};    /*!< Configure PLL to the desired values */    CLOCK_SetPLL0Freq(&pll0Setup);
    CLOCK_SetClkDiv(kCLOCK_DivPll0Clk, 0U, true);    CLOCK_SetClkDiv(kCLOCK_DivPll0Clk, 1U, false);
    /* I2S clocks */    CLOCK_AttachClk(kPLL0_DIV_to_FLEXCOMM6);    CLOCK_AttachClk(kPLL0_DIV_to_FLEXCOMM7);
    /* Attach PLL clock to MCLK for I2S, no divider */    CLOCK_AttachClk(kPLL0_to_MCLK);    SYSCON->MCLKDIV = SYSCON_MCLKDIV_DIV(0U);    SYSCON->MCLKIO  = 1U;
    /* reset FLEXCOMM for I2C */    RESET_PeripheralReset(kFC4_RST_SHIFT_RSTn);
    /* reset FLEXCOMM for DMA0 */    RESET_PeripheralReset(kDMA0_RST_SHIFT_RSTn);
    /* reset FLEXCOMM for I2S */    RESET_PeripheralReset(kFC6_RST_SHIFT_RSTn);    RESET_PeripheralReset(kFC7_RST_SHIFT_RSTn);
    /* reset NVIC for FLEXCOMM6 and FLEXCOMM7 */    NVIC_ClearPendingIRQ(FLEXCOMM6_IRQn);    NVIC_ClearPendingIRQ(FLEXCOMM7_IRQn);
    /* Enable interrupts for I2S */    EnableIRQ(FLEXCOMM6_IRQn);    EnableIRQ(FLEXCOMM7_IRQn);
    /* Initialize the rest */    BOARD_InitPins();    BOARD_BootClockPLL1_150M();    BOARD_InitDebugConsole();    BOARD_InitSysctrl();
    PRINTF("
");    PRINTF("**********************************
");    PRINTF("Maestro audio solutions demo start
");    PRINTF("**********************************
");    PRINTF("
");
    ret = BOARD_CODEC_Init();    if (ret)    {        PRINTF("CODEC_Init failed
");        return -1;    }
    if (xTaskCreate(APP_SDCARD_Task, "SDCard Task", SDCARD_TASK_STACK_SIZE, &app, configMAX_PRIORITIES - 4, NULL) !=        pdPASS)    {        PRINTF("
Failed to create application task
");        while (1)            ;    }
    /* Set shell command task priority = 1 */    if (xTaskCreate(APP_Shell_Task, "Shell Task", SHELL_TASK_STACK_SIZE, &app, configMAX_PRIORITIES - 5,                    &app.shell_task_handle) != pdPASS)    {        PRINTF("
Failed to create application task
");        while (1)            ;    }
    /* Run RTOS */    vTaskStartScheduler();
    /* Should not reach this statement */    return 0;}

2.2. SD卡管理任务SD卡任务的代码如下所示，其主要的作用是：SD在插入时会触发中断，最终触发到当前任务，用于完成SD卡的挂载操作。

void APP_SDCARD_Task(void *param){    const TCHAR driverNumberBuffer[3U] = {SDDISK + '0', ':', '/'};    FRESULT error;    app_handle_t *app = (app_handle_t *)param;
    app->sdcardSem = xSemaphoreCreateBinary();
    BOARD_SD_Config(&g_sd, APP_SDCARD_DetectCallBack, BOARD_SDMMC_SD_HOST_IRQ_PRIORITY, app);
    PRINTF("[APP_SDCARD_Task] start
");
    /* SD host init function */    if (SD_HostInit(&g_sd) != kStatus_Success)    {        PRINTF("[APP_SDCARD_Task] SD host init failed.
");        vTaskSuspend(NULL);    }
    /* Small delay for SD card detection logic to process */    vTaskDelay(100 / portTICK_PERIOD_MS);
    while (1)    {        /* Block waiting for SDcard detect interrupt */        xSemaphoreTake(app->sdcardSem, portMAX_DELAY);
        if (app->sdcardInserted != app->sdcardInsertedPrev)        {            app->sdcardInsertedPrev = app->sdcardInserted;
            SD_SetCardPower(&g_sd, false);
            if (app->sdcardInserted)            {                /* power on the card */                SD_SetCardPower(&g_sd, true);                if (f_mount(&app->fileSystem, driverNumberBuffer, 0U))                {                    PRINTF("[APP_SDCARD_Task] Mount volume failed.
");                    continue;                }
#if (FF_FS_RPATH >= 2U)                error = f_chdrive((char const *)&driverNumberBuffer[0U]);                if (error)                {                    PRINTF("[APP_SDCARD_Task] Change drive failed.
");                    continue;                }#endif
                PRINTF("[APP_SDCARD_Task] SD card drive mounted
");
                xSemaphoreGive(app->sdcardSem);            }        }    }}

2.3. shell任务shell任务的主要目的通过USART0（与Link2的虚拟串口链接），为用户提供一个可以控制播放器的操作接口，主要处理函数如下所示：

uint32_t ulTaskGenericNotifyTake( UBaseType_t uxIndexToWait,                                      BaseType_t xClearCountOnExit,                                      TickType_t xTicksToWait )    {        uint32_t ulReturn;
        configASSERT( uxIndexToWait < configTASK_NOTIFICATION_ARRAY_ENTRIES );
        taskENTER_CRITICAL();        {            /* Only block if the notification count is not already non-zero. */            if( pxCurrentTCB->ulNotifiedValue[ uxIndexToWait ] == 0UL )            {                /* Mark this task as waiting for a notification. */                pxCurrentTCB->ucNotifyState[ uxIndexToWait ] = taskWAITING_NOTIFICATION;
                if( xTicksToWait > ( TickType_t ) 0 )                {                    prvAddCurrentTaskToDelayedList( xTicksToWait, pdTRUE );                    traceTASK_NOTIFY_TAKE_BLOCK( uxIndexToWait );
                    /* All ports are written to allow a yield in a critical                     * section (some will yield immediately, others wait until the                     * critical section exits) - but it is not something that                     * application code should ever do. */                    portYIELD_WITHIN_API();                }                else                {                    mtCOVERAGE_TEST_MARKER();                }            }            else            {                mtCOVERAGE_TEST_MARKER();            }        }        taskEXIT_CRITICAL();
        taskENTER_CRITICAL();        {            traceTASK_NOTIFY_TAKE( uxIndexToWait );            ulReturn = pxCurrentTCB->ulNotifiedValue[ uxIndexToWait ];
            if( ulReturn != 0UL )            {                if( xClearCountOnExit != pdFALSE )                {                    pxCurrentTCB->ulNotifiedValue[ uxIndexToWait ] = 0UL;                }                else                {                    pxCurrentTCB->ulNotifiedValue[ uxIndexToWait ] = ulReturn - ( uint32_t ) 1;                }            }            else            {                mtCOVERAGE_TEST_MARKER();            }
            pxCurrentTCB->ucNotifyState[ uxIndexToWait ] = taskNOT_WAITING_NOTIFICATION;        }        taskEXIT_CRITICAL();
        return ulReturn;    }

2.4. codec初始化codec使用的是板载的wm8904，初始化代码如下所示。

int BOARD_CODEC_Init(void){    CODEC_Init(&codecHandle, &boardCodecConfig);
    /* Invert the DAC data in order to output signal with correct polarity - set DACL_DATINV and DACR_DATINV = 1 */    WM8904_WriteRegister((wm8904_handle_t *)codecHandle.codecDevHandle, WM8904_AUDIO_IF_0, 0x1850);
    /* Initial volume kept low for hearing safety. */    CODEC_SetVolume(&codecHandle, kCODEC_PlayChannelHeadphoneLeft | kCODEC_PlayChannelHeadphoneRight, 75);
    return 0;}

3. 功能配置功能配置使用的NXP提供的MCUXpresso Config Tools，各个配置项如下所示。 3.1. 管脚配置主要是对用到的USART、I2C、SDIF等外设管脚进行初始化。 3.2. 时钟配置时钟配置如下所示，只配置了基本的时钟以及使用到的外设时钟。  4. 功能展示4.1. 连线方式需要链接的是：- 使用Micro USB链接电脑和开发板的调试串口（主要进行程序下载以及SHELL交互）- 使用3.5MM的接口链接开发板和扬声器（右边的是音频输出） 5. 心得体会这是第一次使用NXP的MCU进行开发，工具做的很完善，例程支持也很完善。芯片的外设资源也很丰富。总之就是很强大，之后可以借助于这个芯片做很多有意思的东西。 总体而言，透过Funpack第十一期的活动收益良多。感谢硬禾提供这么好的活动！

责任编辑：haq