GD32 CAN波特率计算问题

一、问题描述

以下是GD32F205 CAN0的配置代码，将CAN0的波特率设置为125kbps。其中影响波特率的几个关键参数为resync_jump_width、time_segment_1、time_segment_2和prescaler，下面就详细探讨下几个参数的关系。

can_parameter_struct        can_parameter;

can_parameter.time_triggered = DISABLE;
can_parameter.auto_bus_off_recovery = DISABLE;
can_parameter.auto_wake_up = DISABLE;
can_parameter.no_auto_retrans = DISABLE;
can_parameter.rec_fifo_overwrite = DISABLE;
can_parameter.trans_fifo_order = DISABLE;
can_parameter.working_mode = CAN_LOOPBACK_MODE;
/* configure baudrate to 125kbps */
can_parameter.resync_jump_width = CAN_BT_SJW_1TQ;
can_parameter.time_segment_1 = CAN_BT_BS1_5TQ;
can_parameter.time_segment_2 = CAN_BT_BS2_4TQ;
can_parameter.prescaler = 48;
can_init(CAN0, &can_parameter);

二、官方描述

GD32官方的描述入下，

简言之

因此

由于PSC要为整数，所以在确定的波特率下，要选择合适的SJW、BS1和BS2。SWJ的取值范围为1~4，BS1的取值范围为1~16，BS2的取值范围为1~8。关于SWJ、BS1和BS2这三个参数的描述入下，建议详细阅读。

 三、例子

以下举几个例子

/*******************************************
 * PCLK时钟为60MHz，配置波特率为125kbps
 * 60000/((1+5+4)*48) = 125
 *******************************************/
can_parameter.resync_jump_width = CAN_BT_SJW_1TQ;
can_parameter.time_segment_1 = CAN_BT_BS1_5TQ;
can_parameter.time_segment_2 = CAN_BT_BS2_4TQ;
can_parameter.prescaler = 48;
can_init(CAN0, &can_parameter);

/*******************************************
 * PCLK时钟为60MHz，配置波特率为250kbps
 * 60000/((1+5+4)*24) = 250
 *******************************************/
can_parameter.resync_jump_width = CAN_BT_SJW_1TQ;
can_parameter.time_segment_1 = CAN_BT_BS1_5TQ;
can_parameter.time_segment_2 = CAN_BT_BS2_4TQ;
can_parameter.prescaler = 24;
can_init(CAN0, &can_parameter);

/*******************************************
 * PCLK时钟为60MHz，配置波特率为500kbps
 * 60000/((1+6+5)*10) = 500
 *******************************************/
can_parameter.resync_jump_width = CAN_BT_SJW_1TQ;
can_parameter.time_segment_1 = CAN_BT_BS1_6TQ;
can_parameter.time_segment_2 = CAN_BT_BS2_5TQ;
can_parameter.prescaler = 10;
can_init(CAN0, &can_parameter);