STM32 RDS解码

       RDS(Radio Data System)无线数据广播系统是在调频广播发射信号中利用副载波把电台名称、节目类型、节目内容及其它信息以数字形式发送出去。通过具有RDS功能的调谐器就可以识别这些数字信号，变成字符显示在显示屏上。在收到节目的同时，通过RDS可知道接收到的是那个电台，它的发射频率，并给出该电台其余的频率，由此再使用“切换频率”钮来保证所接收的信号为最强的频率。RDS无线数据广播文件可显示接收到的节目名称及其它资料。RDS功能可按节目类型决定取舍，寻找到符合你要求的电台。RDS还能用来自动控制接收机，使流动工作的汽车收音机一直保持最佳接收状态，及时收到紧急交通报告，有利交通安全。

       最近需要在我们的车载设备中集成RDS功能，这里需要用到一个专门的RDS解码芯片(这里使用ST的TDA7478), 通过RDS解码芯片，可以将空中的RDS广播信号解调出来输出给STM32，共有3路输出，分别是QUAL(信号质量)、RDCL(时钟信号)、RDDA(RDS数据)输出，STM32在RDS时钟到来是读取RDS数据并存入到buffer中，当buffer中的数据校验成功时，认为收到正确的RDS数据。

       STM32具体操作流程如下：

1.配置QUAL、RDCL、RDDA为输入端口，并设置RDCL为上升沿中断；

2.在RDCL产生中断时，读取RDDA数据，并将数据存入到buffer中；

3.每收到一块（26位）RDS数据后，做一次同步校验，若同步失败，则继续做同步，若同步成功，则继续接收下一块数据；

4.当接收到连续的ABCD四块数据并校验无误后，将四块数据拼接成一组，发送给主CPU做进一步的解析处理（需参考RDS标准，如国标、欧洲标准，美洲标准）。

参考代码如下：

//********************************************************************//filename:  RDS.cpp//created: 2012-04-24//author:  firehood//purpose: RDS解码//*********************************************************************#include "RDS.h"// 同步校验码（由偏置字*H矩阵计算得到）const static int32u SYNCODE_A  = 0x03D8;const static int32u SYNCODE_B  = 0x03D4;const static int32u SYNCODE_C  = 0x025C;const static int32u SYNCODE_C2 = 0x03CC;const static int32u SYNCODE_D  = 0x0258;static Boolean g_bRDSExist = FALSE;    // RDS是否存在static Boolean g_bRDSEnable = FALSE;   // RDS功能使能标志static BLOCK   g_block = 0;   // RDS数据块static BLOCK   g_blockA = 0,g_blockB = 0,g_blockC = 0,g_blockD = 0;static int32u  g_bRevBitCount = 0;   static Boolean g_bSyncFlag = FALSE;    // 是否同步标志static Boolean g_nSyncLevel = 0;       // 同步级数static Boolean g_bGroupFlag = FALSE;static int8u   g_RDSGroup[16] = {0};   // 每组信息包含A、B、C、D四块;                                       // 每块信息占26bit,以四个字节存放(存在低26位) // RDS初始化void dev_RDS_init(void){GPIO_InitTypeDef GPIO_InitStructure;// 配置GPIOA15为RDS时钟输入，GPIOA8为RDS数据输入GPIO_InitStructure.GPIO_Pin = GPIO_Pin_15 | GPIO_Pin_8;GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;GPIO_Init(GPIOA, &GPIO_InitStructure);// 配置GPIOD2为RDS信号质量输入GPIO_InitStructure.GPIO_Pin = GPIO_Pin_2;GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;GPIO_Init(GPIOD, &GPIO_InitStructure);// 打开GPIOA、GPIOD时钟RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA|RCC_APB2Periph_GPIOD,                       ENABLE);}// RDS使能void dev_RDS_Enable(Boolean bEnable){    EXTI_InitTypeDef        EXTI_InitStructure;NVIC_InitTypeDef        NVIC_InitStructure;     if(g_bRDSEnable == bEnable)   return;// 配置GPIOA15(RDS时钟信号）上升沿中断GPIO_EXTILineConfig(GPIO_PortSourceGPIOA,GPIO_PinSource15);EXTI_ClearITPendingBit(EXTI_Line15);EXTI_InitStructure.EXTI_Line = EXTI_Line15;EXTI_InitStructure.EXTI_Mode = EXTI_Mode_Interrupt;  EXTI_InitStructure.EXTI_Trigger= EXTI_Trigger_Rising;EXTI_InitStructure.EXTI_LineCmd = bEnable ? ENABLE : DISABLE;EXTI_Init(&EXTI_InitStructure);// 配置中断向量NVIC_ClearIRQChannelPendingBit(EXTI15_10_IRQChannel);NVIC_InitStructure.NVIC_IRQChannel = EXTI15_10_IRQChannel;  NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 1;NVIC_InitStructure.NVIC_IRQChannelSubPriority = 3;NVIC_InitStructure.NVIC_IRQChannelCmd = bEnable ? ENABLE : DISABLE;NVIC_Init(&NVIC_InitStructure);    g_bRDSEnable = bEnable;}/******************************************************************************** Function Name  : main* Description    : Main program.* Input          : None* Output         : None* Return         : None*******************************************************************************/int main(void){/* Configure the system clocks */RCC_Configuration();/* NVIC Configuration */NVIC_Configuration();/* RDS initialization */dev_RDS_init();/* Enable RDS */dev_RDS_Enable(TRUE);/* RDS decode*/dev_RDS_decode();}// RDS解码void dev_RDS_decode(void){     int32u nSynCode = 0; Boolean bReSync = FALSE;// 是否重新同步标志 if(!g_bRDSExist)     return; //dbgprt("g_bRevBitCount = %d...\n",g_bRevBitCount); if(!g_bSyncFlag)  // 是否同步 {if(g_bRevBitCount<BLOCK_COUNT)return;// 计算同步校验码nSynCode = CacluSyncCode(g_block);//dbgprt("g_block = 0x%x,SynCode = 0x%x\n",g_block,nSynCode);if(nSynCode == SYNCODE_A){g_bSyncFlag = TRUE; g_blockA = g_block;g_nSyncLevel = 1;g_bRevBitCount = 0;dbgprt("RDS sync success!!!!!!!!!!\n");}}else  // RDS已同步{if(g_bRevBitCount >= BLOCK_COUNT){    nSynCode = CacluSyncCode(g_block);    //dbgprt("g_block = 0x%x,SynCode = 0x%x\n",g_block,nSynCode);switch(nSynCode){case SYNCODE_A:if(g_nSyncLevel != 0){bReSync = TRUE;break;}g_blockA = g_block;g_nSyncLevel = 1;g_bRevBitCount = 0;dbgprt("rev BlockA[0x%04x] success...\n",g_blockA);break;case SYNCODE_B:if(g_nSyncLevel != 1){bReSync = TRUE;break;}g_blockB = g_block;g_nSyncLevel = 2;g_bRevBitCount = 0;dbgprt("rev BlockB[0x%04x] success...\n",g_blockB);break;case SYNCODE_C:case SYNCODE_C2:if(g_nSyncLevel != 2){bReSync = TRUE;break;}g_blockC = g_block;g_nSyncLevel = 3;g_bRevBitCount = 0;dbgprt("rev BlockC[0x%04x] success...\n",g_blockC);break;case SYNCODE_D:if(g_nSyncLevel != 3){bReSync = TRUE;break;}g_blockD = g_block;g_nSyncLevel = 0;g_bGroupFlag = TRUE;g_bRevBitCount = 0;dbgprt("rev BlockD[0x%04x] success...\n",g_blockD);break;default:  // 同步校验失败，需重新同步bReSync = TRUE;break; }  }if(bReSync){// 重新同步dbgprt("ReSync RDS...\n");g_bSyncFlag = FALSE;g_nSyncLevel = 0;}if(g_bGroupFlag) // 接收到一组RDS数据，发送给89{dbgprt("rev RDS group done...\n");g_bGroupFlag = FALSE;memcpy(g_RDSGroup,&g_blockA,4);memcpy(g_RDSGroup+4,&g_blockB,4);memcpy(g_RDSGroup+8,&g_blockC,4);memcpy(g_RDSGroup+12,&g_blockD,4);// 将RDS数据发送给主CPUSendRdsDataToHost(g_RDSGroup,sizeof(g_RDSGroup));}}}// RDS数据接收处理（RDS时钟中断）void dev_RDS_RevDataHandler(void){   static int8u nGoodQualCounts = 0;   // 统计RDS信号质量持续有效次数int8u RDSDataBit = GPIO_ReadInputDataBit(GPIOA,GPIO_Pin_8);// 读取RDS信号质量信号if(!GPIO_ReadInputDataBit(GPIOD,GPIO_Pin_2))  // GPIOD2为RDS信号质量输入{ nGoodQualCounts = 0;     g_bRDSExist = FALSE;}else { nGoodQualCounts++;}    // 连续N(N=10)次统计RDS信号输出均为高电平，认为存在RDS信号if(nGoodQualCounts>10){ g_bRDSExist = TRUE;     nGoodQualCounts = 0;} //if(g_bRDSExist){     g_block <<= 1; g_block |= RDSDataBit; g_block &= 0x3FFFFFF; g_bRevBitCount++;}}// 计算同步校验码int32u CacluSyncCode(BLOCK block){// 同步校验矩阵Hconst int8u H[] = {1,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,1,1,0,1,1,0,1,1,1,0,0,0,1,0,1,1,0,1,1,1,0,0,0,1,0,1,1,0,1,1,1,1,0,1,0,0,0,0,1,1,1,1,1,1,0,0,1,1,1,1,1,1,1,0,0,0,1,0,0,1,1,1,1,0,1,0,1,0,1,0,1,1,1,0,1,1,1,0,1,1,0,0,1,1,0,1,1,1,0,1,1,1,0,0,0,0,0,0,0,0,1,1,1,1,1,0,1,1,1,0,0,0,1,1,1,1,0,1,1,1,0,        0,0,1,1,1,1,0,1,1,1,1,0,1,0,1,0,0,1,1,1,1,1,1,0,0,0,1,1,1,1,1,1,0,0,0,1,1,0,1,1};    int8u synMatrix[10] = {0};int32u nSynCode = 0;int8u i = 0,j = 0;    for(i=0;i<10;i++)    {         for(j=0;j<BLOCK_COUNT;j++)         {              synMatrix[i]+= ((block>>(BLOCK_COUNT-1-j))&1)*H[i+10*j];         }         synMatrix[i] = synMatrix[i]%2;         nSynCode <<= 1;         nSynCode += synMatrix[i];    } return nSynCode;}/******************************************************************************** Function Name  : EXTI15_10_IRQHandler* Description    : This function handles External lines 15 to 10 interrupt request.* Input          : None* Output         : None* Return         : None*******************************************************************************/void EXTI15_10_IRQHandler(void){if(EXTI_GetITStatus(EXTI_Line15) != RESET){EXTI_ClearITPendingBit(EXTI_Line15);    dev_RDS_RevDataHandler();   }}