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)
{
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CPU
SendRdsDataToHost(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H
const 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-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();
}
}