GD32F303之CAN通信

1、CAN时钟

GD32F303主时钟频率最大是120Mhz,然后APB1时钟最大是60Mhz,APB2时钟最大是120Mhz,CAN挂载在APB1总线上面

所以一般CAN的时钟频率是60Mhz,这个频率和后面配置波特率有关

2、GD32F303时钟配置

首先我们知道芯片有几个时钟

HXTAL：高速外部时钟；
LXTAL：低速外部时钟；
IRC8M：高速内部时钟；
IRC40K：低速内部时钟；

代码配置时钟时我们要确定时选择内部晶振还是外部晶振，他们配置频率都不一样，例如下面的宏定义可以配置不同的时钟频率

比如如果定义了__SYSTEM_CLOCK_120M_PLL_IRC8M宏定义，那么芯片时钟采用内部晶振8Mhz,然后主时钟频率是120Mhz

如果定义了__SYSTEM_CLOCK_120M_PLL_HXTAL宏定义，那么芯片时钟采用外部晶振时钟，这个晶振一般都是8Mhz,但是针对不同的系列有所不一样，比如GD32F303RET6的外部晶振就是12Mhz,然后使能__SYSTEM_CLOCK_120M_PLL_HXTAL宏定义之后他的主时钟频率不是120Mhz,看代码可知（12/2）*30不等于120Mhz,所以时钟的频率需要确定好，下面这个代码只适配外部晶振是8Mhz的。

3、CAN的波特率配置

首先我们需要知道波特率的计算公式，其中的PCLK就是CAN挂载总线APB1的时钟，一般为60Mhz,如果我们配置为下面的参数，及代表着CAN的波特率为250kbits。

  /* baudrate 250Kbps */
	can_parameter.resync_jump_width=CAN_BT_SJW_1TQ;
	can_parameter.time_segment_1 = CAN_BT_BS1_14TQ;
	can_parameter.time_segment_2 = CAN_BT_BS2_1TQ;
	can_parameter.prescaler = 15;

4、CAN通信代码

can.c

//can.c文件
#include "can.h"
#include "led.h"

void gd32_can_init(void)
{
	can_parameter_struct	can_parameter;
    can_filter_parameter_struct can_filter;
	/* initialize CAN register */
    can_deinit(CAN0);
    /* enable CAN clock */
    rcu_periph_clock_enable(RCU_CAN0);
    rcu_periph_clock_enable(RCU_GPIOA);//使能时钟

    gpio_init(GPIOA, GPIO_MODE_IPU, GPIO_OSPEED_50MHZ,GPIO_PIN_11);
    gpio_init(GPIOA, GPIO_MODE_AF_PP, GPIO_OSPEED_50MHZ,GPIO_PIN_12);//IO复用为CAN功能
  
    /* configure CAN0 NVIC */
    nvic_irq_enable(CAN0_RX1_IRQn,0,0); //中断配置

    can_struct_para_init(CAN_INIT_STRUCT, &can_parameter);
    can_struct_para_init(CAN_FILTER_STRUCT, &can_filter);//初始化参数
  /* baudrate 250Kbps */
	can_parameter.time_segment_1 = CAN_BT_BS1_14TQ;
	can_parameter.time_segment_2 = CAN_BT_BS2_1TQ;
	can_parameter.prescaler = 15;
    /* initialize CAN */
    can_init(CAN0, &can_parameter);
	
	can_filter.filter_fifo_number = CAN_FIFO1;
    can_filter.filter_enable = ENABLE;
    can_filter_init(&can_filter);
	 /* enable can receive FIFO0 not empty interrupt */
    can_interrupt_enable(CAN0, CAN_INT_RFNE1|CAN_INT_TME);

}

/*
	CAN通信数据发送
		can_frame---要发送的数据
	发送成功返回0，失败返回1 
*/
uint8_t gd32_can_send(can_trasnmit_message_struct can_frame)
{  
	uint8_t ret=0;
	ret = can_message_transmit(CAN0,&can_frame);
	if(ret == CAN_NOMAILBOX)
	{
		return 1;
	}
  	return 0;
}


/*
	CAN出错--重启CAN
*/
void gd32_can_error(void)
{
	if(	can_flag_get(CAN0, CAN_FLAG_MTE2) != RESET ||
		can_flag_get(CAN0, CAN_FLAG_MTE0) != RESET ||
		can_flag_get(CAN0, CAN_FLAG_MTE1) != RESET || 
		can_flag_get(CAN0, CAN_FLAG_PERR) != RESET ||
		can_flag_get(CAN0, CAN_FLAG_WERR) != RESET)
	{
		can_flag_clear(CAN0, CAN_FLAG_MTE0);
		can_flag_clear(CAN0, CAN_FLAG_MTE1);
		can_flag_clear(CAN0, CAN_FLAG_MTE2);
		can_flag_clear(CAN0, CAN_FLAG_PERR);
		can_flag_clear(CAN0, CAN_FLAG_WERR);
		can_wakeup(CAN0);
		gd32_can_init();
	}
}



/*
	CAN接收中断函数
*/
void CAN0_RX1_IRQHandler(void)
{
	can_receive_message_struct can_mes;
	memset(&can_mes,0,sizeof(can_mes)); 
	can_message_receive(CAN0, CAN_FIFO1, &can_mes); 
	LED1_ON();
}

can.h

#ifndef __CAN_H
#define __CAN_H

#include "gd32f30x.h"
#include "string.h"

void gd32_can_init(void);
uint8_t gd32_can_send(can_trasnmit_message_struct can_frame);
void gd32_can_error(void);

#endif

main.c

	//CAN初始化
	gd32_can_init();
	transmit_message.tx_sfid = 0x7ab;
	transmit_message.tx_efid = 0x00;
	transmit_message.tx_ft = CAN_FT_DATA;//帧的类型：数据帧或者遥控帧
	transmit_message.tx_ff = CAN_FF_STANDARD;//帧的格式：标准帧或者拓展帧
	transmit_message.tx_dlen = 8;//数据长度小于8
	transmit_message.tx_data[0] = 0x55;
	transmit_message.tx_data[1] = 0x55;
	transmit_message.tx_data[2] = 0x55;
	transmit_message.tx_data[3] = 0x55;
	transmit_message.tx_data[4] = 0x55;
	transmit_message.tx_data[5] = 0x55;
	transmit_message.tx_data[6] = 0x55;
	transmit_message.tx_data[7] = 0x55;


    gd32_can_send(transmit_message);