Robotics Institute 

University of Michigan, Ann Arbor

© 2017 by Bruce Personal Website. 

Updated on 8/21/2017

Mavlink

October 17, 2015

Introduction

  1. It is a protocol for communication

  2. Transmit in UART Serial interface

  3. Are Hexadecimal and Octadecimal numbers

 

Heartbeat Pack

 

  • Heart beat pack is a special pack which is for “register”, so a device which sanding this pack in a frequency of 2Hz or more can be recognized as a “member” in the whole system.

  • Only member can send a message/command.

Pack example (Heartbeat)

  • packet length = 17 (6 bytes header + 9 bytes payload + 2 bytes checksum)

hdr len seq sys cmp id   payload (len 9)----------------------  crc-----
 0     1    2     3    4        6     7    8    9    a   b   c   d    e    f    10
FE   09  4E  01  01  00   00   00  00  00  02 03 51 04  03 1C  7F

 

Fixed Header (6 octets)
0. packet header, always 0xFE
1. message length (for this pack = 9)
2. sequence number -- rolls around from 255 to 0 (0x4e, previous was 0x4d)
3. source system - what system is sending this message (for this example 1)
4. source component - what component of the system is sending the message (for this example 1)
5. message ID (0 = heartbeat)

 

Variable Sized Payload (specified in octet 1, range 0..255)
06-0e. payload

 

Packet Checksum
0f-10. CRC25

 

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