stm32_can波特率设置指南.doc

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1、STM32的CAN波特率计算STM32里的CAN支持2.0A,2.0B,带有FIFO,中断等,这里主要提一下内部的时钟应用.bxCAN挂接在APB1总线上,采用总线时钟,所以我们需要知道APB1的总线时钟是多少.我们先看看下图,看看APB1总线时钟:APB1时钟取自AHB的分频,而AHB又取自系统时钟的分频,系统时钟可选HSI,HSE,PLLCLK,这个在例程的RC设置里都有的,然后再看看有了APB1的时钟后,如何算CAN的总线速率,先看下图:有了上边的这个图,基本就清楚了.                      总线时钟MHz  (3+TS1+TS2)*(BRP+1

2、)===================================================下面是我的计算：CAN_InitStructure.CAN_SJW=CAN_SJW_1tq;CAN_InitStructure.CAN_BS1=CAN_BS1_3tq;注意//#defineCAN_BS1_3tq                ((uint8_t)0x02)/*!<3timequantum*/CAN_InitStructure.CAN_BS2=CAN_BS2_5tq;CAN_InitStructure.CAN_Prescaler=4;//2nominal

3、bittime（3+5+1）tq=9tq关于分频系数查看system_stm32f10x.c下面的staticvoidSetSysClockTo72(void)函数/*HCLK=SYSCLK*//*PCLK2=HCLK*//*PCLK1=HCLK/2*/所以can时钟72MHZ/2/4=9Mhztq=1/36Mhz波特率为1/nominalbittime=9/9=1MHZ=========================================-----------------------------------------------             =

4、===================================================voidCAN_Configuration(void){CAN_InitTypeDef        CAN_InitStructure;CAN_FilterInitTypeDef  CAN_FilterInitStructure;/*CANregisterinit*/CAN_DeInit();CAN_StructInit(&CAN_InitStructure);/*CANcellinit*/CAN_InitStructure.CAN_TTCM=DISABLE;CAN_I

5、nitStructure.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_Normal;CAN_InitStructure.CAN_SJW=CAN_SJW_1tq;CAN_InitStructure.CAN_BS1=CAN_BS1_9tq;

6、CAN_InitStructure.CAN_BS2=CAN_BS2_8tq;CAN_InitStructure.CAN_Prescaler=200;CAN_Init(&CAN_InitStructure);/*CANfilterinit*/CAN_FilterInitStructure.CAN_FilterNumber=0;CAN_FilterInitStructure.CAN_FilterMode=CAN_FilterMode_IdMask;CAN_FilterInitStructure.CAN_FilterScale=CAN_FilterScale_16bit;CAN

7、_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_FilterInitStruct