Pixhawk and external compass, not compatible?

I'm trying to change the APM to a Pixhawk on my copter, I have a gps and external compass so I didn't ask for a combine one, I was reading instructions and see that says that ext compass isn't compatible with Pix but the two ones are 3.3? It's not possible to use? or I'm understanding something wrong? http://copter.ardupilot.com/wiki/common-external-magnetometer-for-improved-performance/Any possibility to hack?.....if I have to wait 2-3 months to another unit arrives to give a try to my copter I'm going to have a nervous attack :(

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  • In order to use the 3.3v ext compass on pixhawk and avoid the 3.3v to 5v problem, connect the VCC wire to the second pin (from left to right) on SPI port, as it is 3.3v, and leave the other 3 wires on the I2c port as you would normally.

  • Dear Cala,

    Anything improved yet? 

    • This is step by step, lot of patience ;),

      GPS looks working now, but I have a horrible weather week :(

      Compass: I couldn't solve compass err so I unplug the ext compass and calibrate again, but comp err was still there, I only change firm to r12 and all works well with int compass now, so, perhaps I'm going to give another oportunity to the ext one, first I have to measure current on compass port, my compass says 3.3 and pix says 5v and 3.3 on the middle pins, I'm an electronic analfabetic :O ; perhaps I need a 5 to 3.3 regulator? But after experiment again with ext compass I'm anxious to autotune and try to fly ;) . The other thing that I did, I bougth an N8M with compass and a friend is going to bring me from Asia :) but have to wait for that.

      Thank's for your interest Khoa :)

  • I have lot of lucky, my friend Carlos solved the problem, many thank's to Electronica Naval  :)

    The current didn't pass down side to upside so he did this and work

    3702095162?profile=originalnow the GPS turn on it's light and flashes the blue one but I still have a problem, Tower and MP don't recognize the gps yet, Ithink that signal wires prerhaps are still bad connected, I google connections but I'm not shure if they have to mantain the same inverted order than APM or I have to reverse signal wires; GPS have 5v, Tx, Rx, Grn labels but have six wires; another possibility is that I have to do the same with other wires? sorry, I'm an electronic rock.

    • GPS SOLVEEEEDDDD!!!!!

      After some days searching and searching, I didn't find how are the equivalent from 4 outputs upside the unit and 6 outputs downside, finally I test with the tester all outputs and discover that RX was in the opposite side that labels says upside. Now I still have to make the ext compass work well but that don't worry me because I can use only the internal until I wait for a newer unit.

    • Oh, haha congrats!

  • Any possibility that 3DR GPS have something like a fuse or something like that, that is possible to repair for an expert? .........or only burned :(  and wait for replace?

    I have  the same on the plane but I'm going to give to an electronic expert to connect, not to burn two ;)

    • Don´t worry, the 3DR LEA6 V1.2 GPS/MAG combo is running with 5V and its MAG is powered by a onboard 3.3V LDO and not by the outer pin of the I²C connector. So you can´t damage it,connecting it to a PIXHAWK.

      Btw. it doesn´t even use the 3.3V of the APM I²C.
    • Mine are separately GPS alone and ext compass alone, the compass is working now but the GPS I confuse the 5v with the ground (UFF!!!) now I change the wires but the GPS don't turn on it's light.

    • Ok,reversing Vcc will damage components. If its the genuine 3DR LEA V1.1, check the schematic here:

      http://stuff.storediydrones.com/3DR-GPS-LEA6-JST-v11-RELEASE.zip

      You might be lucky and only the diode MMSZ5233 (D2-can be removed) and the LDO TPS79133 (PESI) (U1)right beside the connector are fried. They can be replaced pretty cheap, if you´ve got a friend or a cellfone repairshop around.

      A workaround to check if these components are dead, is to apply 3.3V directly to the output pin of the TPS 79133 LDO. Where its output pin 5 is located, can be found via google picture search, same LDO is often used for APM.

      http://stuff.storediydrones.com/3DR-GPS-LEA6-JST-v11-RELEASE.zip
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