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STM32 CAN模块使用详解

时间:11-24 来源:互联网 点击:
STM32 CAN模块使用详解.重点介绍以STM32F103E系列芯片为基础介绍CAN 总线的使用方法。CAN 总线在控制领域使用的非常广泛,如今大多数CPU芯片外围都扩展CAN接口。

1. 硬件基础
CAN总线工作需要两根数据线,RX和TX,即为输入总线和输出总线。一般CPU与外界通信需要接一个驱动芯片(这点很像UART接口),常用的CAN芯片主要有:SN65VHD230、PCA82C250T等,本系统使用SN65VHD230作为CAN接口芯片。而CPU提供的CAN接口为CAN_L和CAN_H。
2. 软件设计
在进行软件设计时,我们首先来看这样的一个结构体:
typedef struct
{
uint32_t StdId;
uint32_t ExtId;
uint8_t IDE;
uint8_t RTR;
uint8_t DLC;
uint8_t Data[8];
} CanTxMsg;
这是定义一个can数据包的结构体,即一个CAN数据包包含以上几个部分。
现在我们思考一个问题:由于can可连接多个节点,如果一个系统为星形网络连接方式,那么主机应该怎样区别这些从机发送的信息呢?
答案在上面那个结构体中,我们可以给每个分机定义一个ID,那么主机在接收到分机发送的数据后,通过ID号判别接收到的信息是那个从机发送的。
注意: DLC定义发送数据的长度,其范围为:0~8。
下面我们来编写CAN驱动:
对CAN模块初始化
void CAN_CfgInit(void)
{
CAN_InitTypeDef CAN_InitStructure;
CAN_FilterInitTypeDefCAN_FilterInitStructure;

CAN_PortInit();
CAN_DeInit(CAN1);
CAN_StructInit(&CAN_InitStructure);

CAN_InitStructure.CAN_TTCM=DISABLE;
CAN_InitStructure.CAN_ABOM=DISABLE;
CAN_InitStructure.CAN_AWUM=DISABLE;
CAN_InitStructure.CAN_NART=DISABLE;
CAN_InitStructure.CAN_RFLM=DISABLE;
CAN_InitStructure.CAN_TXFP=DISABLE;
CAN_InitStructure.CAN_Mode=CAN_Mode_LoopBack;
CAN_InitStructure.CAN_SJW=CAN_SJW_1tq;
CAN_InitStructure.CAN_BS1=CAN_BS1_8tq;
CAN_InitStructure.CAN_BS2=CAN_BS2_7tq;
CAN_InitStructure.CAN_Prescaler=5;
CAN_Init(CAN1, &CAN_InitStructure);

CAN_FilterInitStructure.CAN_FilterNumber=0;
CAN_FilterInitStructure.CAN_FilterMode=CAN_FilterMode_IdMask;
CAN_FilterInitStructure.CAN_FilterScale=CAN_FilterScale_32bit;
CAN_FilterInitStructure.CAN_FilterIdHigh=0x0000;
CAN_FilterInitStructure.CAN_FilterIdLow=0x0000;
CAN_FilterInitStructure.CAN_FilterMaskIdHigh=0x0000;
CAN_FilterInitStructure.CAN_FilterMaskIdLow=0x0000;
//CAN_FilterInitStructure.CAN_FilterFIFOAssignment=0;
CAN_FilterInitStructure.CAN_FilterFIFOAssignment=CAN_FIFO0;
CAN_FilterInitStructure.CAN_FilterActivation=ENABLE;
CAN_FilterInit(&CAN_FilterInitStructure);

CAN_ITConfig(CAN1, CAN_IT_FMP0, ENABLE);
}
这里为can 定义一个专门的结构体,便于数据处理:
typedef struct CAN_Socket CAN;
struct CAN_Socket {
INT32U u32_StdId;
INT32U u32_ExtId;
INT8Uu8_IDE;
INT8Uu8_RTR;
INT8Uu8_DLC;
INT8Uu8_FMI;
INT8Uu8_data[8];
};
数据打包,并且发送
void CAN_TxSocket( CAN *can_Socket )
{
INT8U i = 0;
CanTxMsg TxMessage;

CAN_ITConfig(CAN1, CAN_IT_FMP0, ENABLE); // CAN FIFO0 message pending interrupt enable
// Transmit a message
TxMessage.StdId=can_Socket->u32_StdId;
TxMessage.ExtId=can_Socket->u32_ExtId;
TxMessage.IDE=can_Socket->u8_IDE;
TxMessage.RTR= can_Socket->u8_RTR;
TxMessage.DLC=can_Socket->u8_DLC;
for( i =0; i
TxMessage.Data = can_Socket->u8_data;
}
CAN_Transmit(CAN1, &TxMessage);
CAN_ITConfig(CAN1, CAN_IT_FMP0, DISABLE); // Disable interrupt handling
}
接收函数放在中断程序中处理:
void USB_LP_CAN1_RX0_IRQHandler(void)
{
CanRxMsg RxMessage;
INT8U i = 0;
INT8U u8_RxLen = 0;

RxMessage.StdId = 0x00;
RxMessage.ExtId = 0x00;
RxMessage.IDE = 0;
RxMessage.RTR = 0;
RxMessage.DLC = 0;
RxMessage.FMI = 0;
for( i=0;i<8;i++){
RxMessage.Data=0x00;
}

CAN_Receive(CAN1, CAN_FIFO0, &RxMessage);
u8_RxLen = RxMessage.DLC;
if((RxMessage.ExtId==0x12) && (RxMessage.IDE==CAN_ID_EXT)){
for( i=0;i
CAN_ReceiveBuff = RxMessage.Data;
}
}
}
这里只介绍CAN使用方法和主要驱动程序,测试程序可自行设计。
本人的测试程序:
~INT8U SendBuff1[]="Hello";
INT8U SendBuff2[]="World";
INT8U SendBuff3[]="ADC= 255";
void main(void)
{
System_HardwareInit();
while (1)
{
CAN_Tx(SendBuff1);
Disp_CanReceveData();
CAN_Tx(SendBuff2);
Disp_CanReceveData();
CAN_Tx(SendBuff3);
Disp_CanReceveData();
}
}
接收数据,并在液晶上打印出来!
void Disp_CanReceveData( void )
{
INT8U u8_CanRecBuff[64];

if(CAN_ReceiveBuff[0] == H){
sprintf(( char *)u8_CanRecBuff,"CAN receve buff1 is : %s",CAN_ReceiveBuff);
GCLDASC_PutChar16x16Str(10,30,u8_CanRecBuff, Red, Green, 1);
}
if(CAN_ReceiveBuff[0] == W){
sprintf(( char *)u8_CanRecBuff,"CAN receve buff2 is : %s",CAN_ReceiveBuff);
GCLDASC_PutChar16x16Str(10,50,u8_CanRecBuff, Red, Green, 1);
}
if(CAN_ReceiveBuff[0] == A){
sprintf(( char *)u8_CanRecBuff,"CAN receve buff3 is : %s",CAN_ReceiveBuff);
GCLDASC_PutChar16x16Str(10,70,u8_CanRecBuff, Red, Green, 1);
}
}

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