# CAN FD Protocal

```cpp
// Commands Description:
struct ucan_command {
  uint16_t  opcode_channel;
  uint16_t  args[3];
}

Command=opcode_channel & 0x3ff
Channel=opcode_channel >> 12

Commands Define as below：
1,UCAN_CMD_RESET_MODE :0x001
//no args needed.
2,UCAN_CMD_NORMAL_MODE:0x002
//no args needed.
3,UCAN_CMD_LISTEN_ONLY_MODE: 0x003
//no args needed.
4,UCAN_CMD_TIMING_SLOW:0x004
Uint16_t args[3] define:   //bitrate setting
  uint8_t  ewl;    /* Error Warning limit */
  uint8_t  sjw_t;    /* Sync Jump Width + Triple sampling */
  uint8_t  tseg2;    /* Timing SEGment 2 */
  uint8_t  tseg1;    /* Timing SEGment 1 */
  uint16_t  brp;    /* BaudRate Prescaler */
5,UCAN_CMD_TIMING_FAST: 0x005  //FD bitrate setting
Uint16_t args[3] define:
  uint8_t  unused;
  uint8_t  sjw;    /* Sync Jump Width */
  uint8_t  tseg2;    /* Timing SEGment 2 */
  uint8_t  tseg1;    /* Timing SEGment 1 */
  uint16_t  brp;    /* BaudRate Prescaler */
6,UCAN_USB_CMD_CLK_SET:0x80
Uint16_t args[3] define:
uint8_t mode;
uint8_t unused[5];
mode value define:
0x00:80MHZ
0x01:60MHZ
0x02:40MHZ
0x03:30MHZ
0x04:24MHZ
0x05:20MHZ

7,UCAN_USB_CMD_DEVID_SET:0x81
Uint16_t args[3] define:

uint16_t unused;
    uint32_t device_id;

8,UCAN_CMD_END_OF_COLLECTION: 0x3ff
//no args needed.

Command package format:
Command1+command2+command3+………+UCAN_CMD_END_OF_COLLECTION command

Command data packets was send by bulk endpoint 0x01.


Device Receive can frames:
struct ucan_rx_msg {
  uint16_t  size;
  uint16_t  type;
  uint32_t  ts_low;
  uint32_t  ts_high;
  uint32_t  tag_low;
  uint32_t  tag_high;
  uint8_t  channel_dlc;
  uint8_t  client;
  uint16_t  flags;
  uint32_t  can_id;
  uint8_t  d[];
}
USB packet buffer : ucan_rx_msg1+ucan_rx_msg2+…ucan_rx_msgn+0x000000
Device Send to usb host through USB bulk in endpoint 0x82

Device Send can frames:

Ch1 : USB BULKOUT :0X02
CH2 : USB BULKOUT :0X03

USB Buffer contents:
struct ucan_tx_msg {
  uint16_t  size;
  uint16_t  type;
  uint32_t  tag_low;
  uint32_t  tag_high;
  uint8_t  channel_dlc;
  uint8_t  client;
  uint16_t  flags;
  uint32_t  can_id;
  uint8_t  d[];
}

```


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