【晟矽课堂】FlexCAN的介绍与应用


目  录

  • FlexCAN简介

  • FlexCAN初始化

  • FlexCAN发送报文

  • FlexCAN接收报文

  • FlexCAN中断

  • CAN错误


1. FlexCAN简介


CAN网络拓扑

  • 终端电阻

  • CAN总线

  • CAN收发器

    TJA1050/1、MCP2551

  • CAN控制器

    独立控制器SJA1000、MCP2515

    Bosch M_CAN、X_CAN

    NXP FlexCAN

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FlexCAN拓扑

  • Bus Interface Unit (BIU) 

  • Message Buffers(MBs) 

  • Controller Host Interface (CHI)

  • Protocol Engine (PE)

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FlexCAN Memory Map

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2. FlexCAN初始化


FlexCAN 工作模式

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FlexCAN初始化

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CAN波特率设置

  • CAN_CTRL1(PRESDIV 8bits、PROPSEG 3bits、PSEG1 3bits、PSEG2 3bits、RJW 2bits)

  • CAN_CBT(BTF 1bit、EPRESDIV 10bits、EPROPSEG 6bits、EPSEG1 5bits、EPSEG2 5bits、ERJW 5bits)

  • CAN_FDCBT(PRESDIV 10bits、FPROPSEG 5bits、FPSEG1 3bits、FPSEG2 3bits、FRJW 3bits)

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FlexCAN Message Buffer Structure

  • 0x80~0x87F 128个 128-bit message buffers(MBs)

  • CS、ID、DATA(8、16、32、64)

  • CAN_FDCTRL.MBDSR0/1/2/3

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3. FlexCAN发送报文


FlexCAN发送MB配置

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FlexCAN发送报文类型： 

  • 标准帧(Classical CAN/CAN FD)

  • 扩展帧(Classical CAN/CAN FD)

  • 远程帧(Classical CAN)

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FlexCAN Arbitration Process

发送优先级设置：

  • CAN_CTRL1. LBUF ：Lowest Buffer Transmitted First

  • CAN_MCR.LPRIOEN：Local Priority Enable

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中断使能/标志位：

  • CAN_IMASK1/CAN_IFLAG1：MB0~MB31

  • CAN_IMASK2/ CAN_IFLAG2：MB32~MB63

  • CAN_IMASK3/ CAN_IFLAG3：MB64~MB95

  • CAN_IMASK4/ CAN_IFLAG4：MB96~MB127


FlexCAN 发送实例




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4. FlexCAN接收报文


FlexCAN接收报文


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MB接收配置 - Rx Mask


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MB接收配置 - MB

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FlexCAN Rx FIFO Structure

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0x80~0xDC(MB0~MB5) Rx FIFO engine

  • 0x80~0x8C output

  • 0x90~0xDC internal use

0xE0~0x2DC (MB6~MB37) ID filter table

  • 8~128 table elements

CAN_MCR.RFEN、 CAN_CTRL2.RFFN、CAN_MCR.IDAM

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CAN_MCR.IDAM: D Acceptance Mode

  • 00: Format A

  • 01: Format B

  • 10: Format C

  • 11: Format D – All frames rejected

IDHIT、CAN_RXFIR.IDHIT

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CAN_IMASK1

CAN_IFLAG1

  • BUF0I: Empty the FIFO

  • BUF1I~ BUF4I : Reserved

  • BUF5I: Frames available in Rx FIFO

  • BUF6I: Rx FIFO Warning

  • BUF7I: Rx FIFO Overflow


Rx FIFO接收配置 - Rx Mask

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FlexCAN Rx FIFO with DMA

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CAN_IFLAG1

  • BUF0I~ BUF4I : Unused

  • BUF5I: Frames available in Rx FIFO

  • BUF6I~BUF7I: Unused

FlexCAN Matching Process

Matching优先级：

CAN_CTRL2. MRP: Mailboxes Reception Priority

  • 1: Matching starts from mailboxes and continues on Rx FIFO

  • 0: Matching starts from Rx FIFO and continues on mailboxes

Matching starts from the lowest number toward the higher ones


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FlexCAN 接收实例

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5. FlexCAN中断


CAN错误

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6. CAN错误


CAN网络拓扑


Error counters:

  • CAN_ECR.TXERRCNT

  • CAN_ECR.RXERRCNT

Error flags:

  • CAN_ESR1.TXWRN(CAN_ECR.TXERRCNT>=96)

  • CAN_ESR1.RXWRN(CAN_ECR.RXERRCNT>=96)

  • CAN_ESR1.BIT1ERR/BIT0ERR

  • CAN_ESR1.ACKERR

  • CAN_ESR1.CRCERR

  • CAN_ESR1.FRMERR

  • CAN_ESR1.STFERR

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