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ArduPilot Telemetry Protocol

Posted by Jordi Muñoz on August 11, 2009 at 11:30am
If you ever wonder how to read and decode the protocol check this:The protocol looks like this in terminal:!!!LAT:33952600,LON:-117409072,SPD:0.38,CRT:0.00,ALT:0,ALH:0,CRS:185.80,BER:94,WPN:0,DST:25853,BTV:11.84,***+++ASP:0,THH:85,RLL:26,PCH:-31,STT:2,***+++ASP:6,THH:85,RLL:27,PCH:-30,STT:2,***+++ASP:11,THH:85,RLL:27,PCH:-29,STT:2,***+++ASP:14,THH:77,RLL:28,PCH:-29,STT:2,***+++ASP:15,THH:72,RLL:28,PCH:-28,STT:2,***!!!LAT:33952596,LON:-117409072,SPD:0.24,CRT:0.00,ALT:0,ALH:0,CRS:185.57,BER:94,WPN:0,DST:25853,BTV:11.88,***+++ASP:16,THH:68,RLL:29,PCH:-23,STT:2,***+++ASP:18,THH:60,RLL:30,PCH:-20,STT:2,***+++ASP:17,THH:61,RLL:31,PCH:-21,STT:2,***+++ASP:14,THH:69,RLL:30,PCH:-27,STT:2,***+++ASP:13,THH:71,RLL:29,PCH:-31,STT:2,***There's a low rate string at 1hz that start with !!! and the second string is 4hz and starts with +++, both finish with ***.You need to be able to search for the head of every string like "LAT:", without care of the order, then you read the value after and stop until you reach the comma. In C/C++ are functions that do that for you, if you need an example please read the ardustation source code.Definitions low rate:LAT: LatitudeLON: LongitudeSPD: Speed over ground from GPSCRT: Climb Rate in M/SALT: Altitude in metersALH: The altitude is trying to holdCRS: Course over ground in degrees.BER: Bearing is the heading you want to goWPN: Waypoint number, where WP0 is home.DST: Distance from WaypointBTV: Battery Voltage.RSP: Roll setpoint used to debug, (not displayed here).Definitions high rate:ASP: Airspeed, right now is the raw data.TTH: Throttle in 100% the autopilot is applying.RLL: Roll in degrees + is right - is leftPCH: Pitch in degreesSST: Switch Status, used for debugging, but is disabled in the current version.I know the protocol sucks but is very flexible and i can add and remove new strings when ever i want without damaging the parsing of every groundstation. In ArduPilot Mega i will use ONLY binary protocol with Message ID's, Payload Bytes and CheckSums, better/faster/efficient/flexible..Enjoy!
Tags: ardupilot
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Comments

  • Electronics April 7, 2011 at 8:26am
    Hi all .....

    May I ask experts ... In EZ-ground-station we connect the ground station with audio port in VRX (video receiver) to get the GPS data for tracking antenna pointing ...

    What is the same line in ARDU-STATION ??
  • Rich January 15, 2011 at 1:01pm
    Says this thing has 2 powered servo outputs for steering a directional antenna.  How big of servos are we talking about here?  As in, how much current can a servo draw from it?
  • SciFly January 3, 2011 at 2:39am

    Unfortunately, i ended up with an ardustation with a couple missing surf mount components. The missing parts are the i2c pullup resistors and a diode (for switch five I beleive).Now, on the schematic, the pullups are indicated as not populated, but on the product pictures I see that they are. Can you confirm on this?This is no big deal, I can easily hand solder them- it willl be a bit difficult given their small size and the fact that I already populated the throughole components, but oh well, the DIY spirit is strong with me!!!. Can you give me the DigiKey or equivalent part numbers [1N4148-XX? , 4.7K-XX??(most importantly the package info) ] or send  some along gratis so that I can get the fulll functionality of the board??

     thanks!

  • Paul Mather December 11, 2010 at 7:00pm

    No units:

    http://en.wikipedia.org/wiki/Geographic_coordinate_system

  • Resat Emre Ayvaci December 11, 2010 at 3:28pm

    LAT:33952600,LON:-117409072,SPD:0.38,CRT:0.00,ALT:0,ALH:0,CRS:185.80,BER:94,WPN:0,DST:25853,BTV:11.84

    please can someone explain this in measurement units? i don't know the units, and i can't the assumption. 

  • Paul Mather December 11, 2010 at 3:22pm

    Take each number and divide by 1000000 That will give you actual lat and long. You can plug them into Google Earth.

  • Resat Emre Ayvaci December 11, 2010 at 3:11pm

    LAT:33952600

    LON:-117409072

     

    i can't figure out what these values are. I tired to use this webpage to figure out, but failed. Can someone explain please?

    http://itouchmap.com/latlong.html is the webpage that i used.

  • gke March 6, 2010 at 11:49pm
    Jordi,
    Do you have a draft of the binary protocol yet for the Mega. Converting to human readable in the flight code is a little expensive. I usually use message ID, LENGTH, payload, Checksum. The length is useful. I assume you will keep with using the message IDs only once rather than reusing the ID if a message type is abandoned.

    Greg
    ps ConfigTool now working well with UAVX - thanks again. Unfortunately we don't seem to have elevation data via Google here in Oz.
  • 3D Robotics
    Chris Anderson August 15, 2009 at 8:31pm
    No, the GPS has exclusive access to the Rx side of the serial port, while telemetry has exclusive access to the Tx side. There is no second serial port. (The Arduino library has a "software serial" function that's supposed to turn any digital pin into a serial port, but it doesn't work)
  • I Heart Robotics August 15, 2009 at 6:29pm
    If I understand the schematic correctly, then the microcontroller sends telemetry data while the gps is not sending data. Is is correct that there is no secondary hardware serial port that could be used for an alternate telemetry data stream?
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