基于STM32的CAN通讯,已在实际项目中应用.docVIP

与本程序代码相关部分的原理图及PCB，基于STM32F103VET6，已在项目中应用。 开头篇：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) ====================================================================== 下面是我的计算： CAN_InitStructure.CAN_SJW = CAN_SJW_1tq;CAN_InitStructure.CAN_BS1 = CAN_BS1_3tq; 注意//#define CAN_BS1_3tq???????????????? ((uint8_t)0x02) /*! 3 time quantum */CAN_InitStructure.CAN_BS2 = CAN_BS2_5tq;CAN_InitStructure.CAN_Prescaler = 4;//2nominal bit time（3+5+1）tq=9tq关于分频系数，查看 system_stm32f10x.c下面的static void SetSysClockTo72(void) 函数：/* HCLK = SYSCLK *//* PCLK2 = HCLK *//* PCLK1 = HCLK/2 */ 所以can时钟 72MHZ/2/4=9 Mhz，tq=1/36Mhz波特率为 1/nominal bit time= 9/9=1MHZ ===================================================================== void CAN_Configuration(void) { CAN_InitTypeDef???????? CAN_InitStructure; CAN_FilterInitTypeDef?? CAN_FilterInitStructure; /* CAN register init */ CAN_DeInit(); CAN_StructInit(CAN_InitStructure); /* CAN cell init */ 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_Normal; CAN_InitStructure.CAN_SJW=CAN_SJW_1tq; CAN_InitStructure.CAN_BS1=CAN_BS1_9tq; CAN_InitStructure.CAN_BS2=CAN_BS2_8tq; CAN_InitStructure.CAN_Prescaler=200; CAN_Init(CAN_InitStructure); /* CAN filter init */ CAN_FilterInitStructure.CAN_FilterNumber=0; CAN_FilterInitStructure.CAN_FilterMode=CAN_FilterMode_IdMask; CAN_FilterInitStructure.CAN_FilterScale=CAN_FilterScale_16bit; CAN_FilterInitStructure.CAN_FilterIdHigh=0x0000; CAN_FilterInitStructure.CAN_FilterIdLow=0x0000; CAN_FilterInitStructure.CAN_Fi