Difference between revisions of "CanServo/Protocol/LongMessage"

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== Up ==
* Up page: [[CanServo/Protocol/0]]
== Long Message ==
== Long Message ==
* A method of sending a long message by dividing it into multiple packets.
** Of course, 1 packet is also possible.


* This content refers to the message format of UAVCAN.
* This content refers to the message format of UAVCAN.
Line 5: Line 12:


* Note:
* Note:
** ID2, CRC16 : byte order : low byte first, little endian
** CRC16 : byte order : low byte first, little endian


* Reference:
* Reference:
** [[Code/CRC16]]
** [[Code/CRC16]]
* Transmission method
** Check the length of the message to be sent, and if it cannot be sent in one packet, calculate CRC16 and add it to the end of the message.
*** The starting value for CRC16 calculation is 0xFFFF (-1).
** Repeat the process of cutting from the front, attaching the Tail Byte, and sending it as one packet.
*** At this time, if the length (including Tail Byte) exceeds 8 bytes, the exact length is placed in the first byte.
** NOTE: If it is not an FD, the maximum is 8 bytes, so it can be up to 7 bytes.
*** In the case of FD, the maximum is 64 bytes, so excluding the first byte of length, it can be up to 62 bytes.
* 주의 사항
** Host가 발신하는 경우는, 동시에 전송하지 않으면 되지만,
** 서보가 보내는 경우는, 여러 서보가 동시에 보낼 수 있습니다.
** 같은 CAN ID 로 동시에 여러 Long Message가 전송 될 때에는, Tail Byte 의 변화와 CRC16 등으로 분석합니다.


=== CAN 2.0 ===
=== CAN 2.0 ===


* The first step is to calculate the CRC16 of the message and add it to the end to create the content to be sent.
=== CAN-FD ===
** 보낼 데이터가 8바이트이상인 경우에만 CRC16을 붙인다. 7바이트 이하인 경우에는 CRC없이 1개 packet으로 전송합니다.
 
* Send (maximum) 7 bytes extracted from the content to be sent and a Check Byte.
* CAN-FD data is expanded up to 64 bytes.
** 0~8, 12, 16, 20, 24, 32, 48, 64


* Multi Packet's Data Format
* [[CanServo/Protocol/CAN-FD]]
** < Data : max 7 byte, cut from 'Message + CRC16' >, <Check Byte>
** Check Byte
*** bit 7 = 1, if first packet
*** bit 6 = 1, if last packet
*** bit 5 = Toggle, first packet = 1, toggle bit on each packet
*** bit 4:0 = Seq, 0 ~ 31, inc 1 on each message


=== FD-CAN ===
=== Tail Byte ===


* Under construction !
* Tail Byte
** bit 7 = first packet
** bit 6 = last packet
** bit 5 = 1 if first packet, toggle bit on each packet
** bit 4:0 = Seq, 0 ~ 31, inc 1 on each message

Latest revision as of 10:06, 26 February 2026

Up

Long Message

  • A method of sending a long message by dividing it into multiple packets.
    • Of course, 1 packet is also possible.
  • This content refers to the message format of UAVCAN.
    • Thanks to UAVCAN
  • Note:
    • CRC16 : byte order : low byte first, little endian
  • Transmission method
    • Check the length of the message to be sent, and if it cannot be sent in one packet, calculate CRC16 and add it to the end of the message.
      • The starting value for CRC16 calculation is 0xFFFF (-1).
    • Repeat the process of cutting from the front, attaching the Tail Byte, and sending it as one packet.
      • At this time, if the length (including Tail Byte) exceeds 8 bytes, the exact length is placed in the first byte.
    • NOTE: If it is not an FD, the maximum is 8 bytes, so it can be up to 7 bytes.
      • In the case of FD, the maximum is 64 bytes, so excluding the first byte of length, it can be up to 62 bytes.
  • 주의 사항
    • Host가 발신하는 경우는, 동시에 전송하지 않으면 되지만,
    • 서보가 보내는 경우는, 여러 서보가 동시에 보낼 수 있습니다.
    • 같은 CAN ID 로 동시에 여러 Long Message가 전송 될 때에는, Tail Byte 의 변화와 CRC16 등으로 분석합니다.

CAN 2.0

CAN-FD

  • CAN-FD data is expanded up to 64 bytes.
    • 0~8, 12, 16, 20, 24, 32, 48, 64

Tail Byte

  • Tail Byte
    • bit 7 = first packet
    • bit 6 = last packet
    • bit 5 = 1 if first packet, toggle bit on each packet
    • bit 4:0 = Seq, 0 ~ 31, inc 1 on each message
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