关于CAN总线驱动使用解释

发布于 2019-07-16 19:57:37 浏览：2452 订阅该版

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* 本帖最后由 ylz0923 于 2019-7-30 11:44 编辑 *

# CAN 设备

## CAN 简介

基本扩展 CAN 外设又称 bxCAN，可与 CAN 网络进行交互。该外设支持 2.0A 和 B 版本的CAN 协议，旨在以最少的 CPU 负载高效管理大量的传入消息，并可按需要的优先级实现消息发送。

## 硬件注意事项  
- 总线上必须有两个以上的CAN设备节点  
- 总线两端须接终端电阻

## 软件配置注意事项  
- 每个CAN设备至少配置一个过滤器, 且过滤器处于活动状态(can驱动中已经配置默认过滤器)
- CAN设备的基础配置, 总线管理和自动重发

### CAN基础配置

CAN配置结构体
```
/**
  * @brief  CAN init structure definition
  */
typedef struct
{
  uint32_t Prescaler;                  /*!< Specifies the length of a time quantum.
                                            This parameter must be a number between Min_Data = 1 and Max_Data = 1024. */
  uint32_t Mode;                       /*!< Specifies the CAN operating mode.
                                            This parameter can be a value of @ref CAN_operating_mode */
  uint32_t SyncJumpWidth;              /*!< Specifies the maximum number of time quanta the CAN hardware
                                            is allowed to lengthen or shorten a bit to perform resynchronization.
                                            This parameter can be a value of @ref CAN_synchronisation_jump_width */
  uint32_t TimeSeg1;                   /*!< Specifies the number of time quanta in Bit Segment 1.
                                            This parameter can be a value of @ref CAN_time_quantum_in_bit_segment_1 */
  uint32_t TimeSeg2;                   /*!< Specifies the number of time quanta in Bit Segment 2.
                                            This parameter can be a value of @ref CAN_time_quantum_in_bit_segment_2 */
  FunctionalState TimeTriggeredMode;   /*!< Enable or disable the time triggered communication mode.
                                            This parameter can be set to ENABLE or DISABLE. */
  FunctionalState AutoBusOff;          /*!< Enable or disable the automatic bus-off management.
                                            This parameter can be set to ENABLE or DISABLE. */
  FunctionalState AutoWakeUp;          /*!< Enable or disable the automatic wake-up mode.
                                            This parameter can be set to ENABLE or DISABLE. */
  FunctionalState AutoRetransmission;  /*!< Enable or disable the non-automatic retransmission mode.
                                            This parameter can be set to ENABLE or DISABLE. */
  FunctionalState ReceiveFifoLocked;   /*!< Enable or disable the Receive FIFO Locked mode.
                                            This parameter can be set to ENABLE or DISABLE. */
  FunctionalState TransmitFifoPriority;/*!< Enable or disable the transmit FIFO priority.
                                            This parameter can be set to ENABLE or DISABLE. */
} CAN_InitTypeDef;
```

drv_can.c中的配置
```
static rt_err_t drv_configure(struct rt_can_device *dev_can,
                              struct can_configure *cfg)
{
    ... ...

drv_init->TimeTriggeredMode = DISABLE;
    drv_init->AutoBusOff = ENABLE;              /* 自动离线管理 */
    drv_init->AutoWakeUp = DISABLE;
    drv_init->AutoRetransmission = DISABLE;
    drv_init->ReceiveFifoLocked = DISABLE;
    drv_init->TransmitFifoPriority = ENABLE;    /* 自动重发 */

... ...
 }
```

- 自动重发和自动离线管理同时打开的效果---总线物理断开后, 重新连接后可以自动重新通讯, 在总线断开期间发生函数不会返回.
- 自动重发和自动离线管理同时关闭的效果---总线物理断开后, 重新连接后无法恢复通讯需要重新启动, 在总线断开期间发生函数返回错误.

### 过滤器配置

先上个demo:![app_can.c](/uploads/201907/16/195817abbnienoenhmf3ro.attach)