STM32 双CAN中Filter配置

过滤器配置示例代码：

 1     CAN_FilterConfTypeDef can_filter;
 2
 3   /* CAN‘s filter banks configuration. */
 4 //  can_filter.BankNumber = 5;                      // Valid after the last time configration.
 5     can_filter.FilterNumber = 3;
 6     can_filter.FilterMode = CAN_FILTERMODE_IDMASK;
 7     can_filter.FilterScale = CAN_FILTERSCALE_32BIT;
 8     can_filter.FilterIdHigh = 0;
 9     can_filter.FilterIdLow = 0;
10     can_filter.FilterMaskIdHigh = 0;
11     can_filter.FilterMaskIdLow = 0;
12     can_filter.FilterFIFOAssignment = CAN_FIFO0;
13     can_filter.FilterActivation = ENABLE;
14     HAL_CAN_ConfigFilter(&hcan1, &can_filter);        // Only CAN1 own filter banks, CAN2 just read it.
15
16 //  can_filter.BankNumber = 5;                      // Valid after the last time configration.
17     can_filter.FilterNumber = 4;
18     can_filter.FilterMode = CAN_FILTERMODE_IDMASK;
19     can_filter.FilterScale = CAN_FILTERSCALE_32BIT;
20     can_filter.FilterIdHigh = 0;
21     can_filter.FilterIdLow = 0;
22     can_filter.FilterMaskIdHigh = 0;
23     can_filter.FilterMaskIdLow = 0;
24     can_filter.FilterFIFOAssignment = CAN_FIFO0;
25     can_filter.FilterActivation = ENABLE;
26     HAL_CAN_ConfigFilter(&hcan1, &can_filter);        // Only CAN1 own filter banks, CAN2 just read it.
27
28 //  can_filter.BankNumber = 5;                      // Valid after the last time configration.
29     can_filter.FilterNumber = 5;
30     can_filter.FilterMode = CAN_FILTERMODE_IDMASK;
31     can_filter.FilterScale = CAN_FILTERSCALE_32BIT;
32     can_filter.FilterIdHigh = 0;
33     can_filter.FilterIdLow = 0;
34     can_filter.FilterMaskIdHigh = 0;
35     can_filter.FilterMaskIdLow = 0;
36     can_filter.FilterFIFOAssignment = CAN_FIFO0;
37     can_filter.FilterActivation = ENABLE;
38     HAL_CAN_ConfigFilter( &hcan1, &can_filter );      // Only CAN1 own filter banks, CAN2 just read it.
39
40   can_filter.BankNumber = 5;                        // Valid after this time configration.
41     can_filter.FilterNumber = 6;
42     can_filter.FilterMode = CAN_FILTERMODE_IDMASK;
43     can_filter.FilterScale = CAN_FILTERSCALE_32BIT;
44     can_filter.FilterIdHigh = 0;
45     can_filter.FilterIdLow = 0;
46     can_filter.FilterMaskIdHigh = 0;
47     can_filter.FilterMaskIdLow = 0;
48     can_filter.FilterFIFOAssignment = CAN_FIFO0;
49     can_filter.FilterActivation = ENABLE;
50     HAL_CAN_ConfigFilter( &hcan1, &can_filter );      // Only CAN1 own filter banks, CAN2 just read it.

请注意：

　　1. 以上配置均通过调用 "HAL_CAN_ConfigFilter( &hcan1, &can_filter)" 生效。这是因为STM32F107中的双路CAN共用过滤器组，而且过滤器组寄存器与CAN1配置寄存器在物理上是挨着的，HAL库将这些寄存器合并在一个结构里访问而已。

 1 /**
 2   * @brief Controller Area Network
 3   */
 4
 5 typedef struct
 6 {
 7   __IO uint32_t MCR;
 8   __IO uint32_t MSR;
 9   __IO uint32_t TSR;
10   __IO uint32_t RF0R;
11   __IO uint32_t RF1R;
12   __IO uint32_t IER;
13   __IO uint32_t ESR;
14   __IO uint32_t BTR;
15   uint32_t  RESERVED0[88];
16   CAN_TxMailBox_TypeDef sTxMailBox[3];
17   CAN_FIFOMailBox_TypeDef sFIFOMailBox[2];
18   uint32_t  RESERVED1[12];
19   __IO uint32_t FMR;
20   __IO uint32_t FM1R;
21   uint32_t  RESERVED2;
22   __IO uint32_t FS1R;
23   uint32_t  RESERVED3;
24   __IO uint32_t FFA1R;
25   uint32_t  RESERVED4;
26   __IO uint32_t FA1R;
27   uint32_t  RESERVED5[8];
28   CAN_FilterRegister_TypeDef sFilterRegister[28];
29 } CAN_TypeDef;

　　　显然对于CAN2->FMR及后面的寄存器没有意义。

　　2. 最后一组过滤器配置中使用了 “can_filter.BankNumber” 项。作用是将过滤器组分成两个段，第一段为CAN1使用（范围是：0~BankNumber-1），第二段为CAN2使用（范围是：BankNumber~27）。

也就是说当CAN1上收到消息，STM32会在0~BankNumer-1这些过滤器中依次查询是否通过过滤，如果通过则将消息放入配置好的CAN1的FIFO里面等待使用，否则就丢弃。

当CAN2上收到消息，STM32会在BankNumer~27这些过滤器中依次查询是否通过过滤，如果通过则将消息放入配置好的CAN2的FIFO里面等待使用，否则就丢弃。

上述代码配置了四组过滤器（滤波内容无意义，这里只讨论过滤器组是否可用）。

　　1. 编号为3的过滤器

　　2. 编号为4的过滤器

　　3. 编号为5的过滤器

　　4. 编号为6的过滤器

并在最后一组配置中使BankNumber=5，意味着CAN1可以使用编号为3,4的过滤器，CAN2可以使用编号为5,6的过滤器。

结论：STM32F107中CAN1和CAN2共用过滤器组，通过FMR寄存器中的CAN2SB段将过滤器组分为两段分别给CAN1和CAN2使用，也可以完全配置给一路CAN使用。应该说增加了CAN的使用灵活性，但配套的API却不全面，难以使用。

最后附上BankNumber配置不同的值时的测试结果：