Tom Gibson
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  • Doug Chevrier
  • Andrew law
  • Jean-Louis Naudin
  • James Goppert

Tom Gibson's Discussions

Differencial thrust with twin motors

Started this discussion. Last reply by Tom Gibson Sep 14, 2012. 1 Reply

Has anyone done a mod for using twin motors for thrust?  The application I would like to implement is on a boat with twin screws but I am not sure where to start.  I think it shouldn't be too…Continue

APM2 GPS non-functional

Started this discussion. Last reply by Tom Gibson Sep 15, 2012. 14 Replies

Hello, I have been reading over several of the problems people have experienced with the MediaTek MT3329 (?) GPS that ships with APM2.  I have not been able to get any signal out of the unit. I have…Continue


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Profile Information

About Me:
Father of 3 (mostly) grown kids. Former full-time aircraft mechanic - A&P, IA. Now working in optical and mechanical engineering and systems integration.
Please tell us a bit about your UAV interest
I've always been intrigued by RC vehicles and more recently UAVs. I have recently been discovering the whole maker movement and DIYDrones in particular through a colleague which has sparked my interest further.
San Diego, CA

Comment Wall (8 comments)

At 4:41pm on August 21, 2012, Andrew law said…

Hi Tom,

thank you for your quick response. what i am trying to do is to implement an external GPS onto APM2 via the I2C port that locates closet to the on-board GPS. the reason for this is because the ext. GPS i have only takes 3.3V or else it fries. And the existing ext. GPS port that is closer to the SD card exerting 5V to the port.

due to the lack of EM406 connector i am not able to use the port directly which force me to the idea of using the group of 4 pin holes that is right next to/behind it. I use the multimeter to check the voltage at the holes behind these ports and found them to have the same voltage as their respected VIN.i powered it up and it seems to work except i dont know where to obtain the data.  on the DIY site with the manual, i am able to disconnect the on-board GPS but i failed to tell APM2 that the new GPS is at the I2C port not the GPS port. do you know what i can do?  is there any different between using TX/RX and SCL SDA to transfer GPS data?

At 7:33am on August 22, 2012, Tom Gibson said…

I'm afraid that's way beyond me, my friend. I do well to have things work when they're plugged in to their standard ports! I have the external GPS that came with APM1 and it works well as long as I have clean power to the board. Maybe someone else will pick up on this thread and offer some help. Sorry!

At 7:11am on September 20, 2012, Doug Chevrier said…


I Googled Z-Boat and the pics look like a full sized boat!  My Q-Boat is maybe 6 ft. long and carries no passengers.  Right now it maneuvers via Radio Control.  I think I've decided on the ArduRover APM 2.5, but I'm a bit concerned about the Ublox LEA-6 GPS.  If I read the specs right, its accuracy is +/- 2.5 meters.  That's quite an area.  Anyway, next step is to order the hardware and get started. 

At 2:27pm on October 2, 2012, Doug Chevrier said…



I received my APM2.5 with LEAS-6 today.  Problem:  No manual, user or otherwise, and I can't find it on 3DR.  I've seen references to it, and really need something in-depth so I know where to go, what to do to get this boat running.  My major burning question is, what kind of signal does the RC/Autopilot input require?  My only spare FUTABA channel is from the "B" switch, which changes the 70Hz pulses from 1ms to 2ms width.  Does the APM2.5 recognize that, or is a solid level required?  Lotsa questions here!!

At 2:38pm on October 2, 2012,
3D Robotics
Chris Anderson

Doug, all the APM manuals are linked in the product listing.

At 10:22am on October 3, 2012, Doug Chevrier said…


I'm learning a lot about my system setup and about the APM2.5!  The receiver (Futaba FP-R138DP PCM1024) uses only 3 channels, 2 thru 4.  As I mentioned, #5 is connected to the B switch.  #2 is the Elevator & 3 is the Throttle.  These are connected to a ROBOTEQ AX1500 Dual Channel Digital Motor Controller.  #4 runs directly to the Rudder.  This may help you with your twin screws.  Apparently, the AX1500 is programmed so the right screw is controlled by the Elevator (the right joystick), and the left screw is controlled by the throttle (left joystick).  I tried to communicate with it via RS232 Com1, but there were comm errors.  I'll try again.  I don't think I'll need the 3-position switch (G), since I need only 2 modes.


I'm assuming that in RC mode, the APM2.5 passes signals straight thru to the outputs, but in Autopilot mode, the outputs are controlled by the waypoint programming.  I'm gonna need to buy some servo extension cables for connecting receiver outputs to the APM2.5.  Also, since the receiver & ROBOTEQ are in a box inside the boat, I'll need an extension for the GPS unit since it has to see the sky from the deck of the boat.

At 10:38am on October 3, 2012, Doug Chevrier said…

Chris Anderson left a comment that the manuals are linked in the Product Listing.  What I've seen there isn't quite enough.  What are the Eagle Files?  I downloaded them (2) but don't have an app to open them.

At 7:11am on October 9, 2012, Doug Chevrier said…


Last Friday I connected my APM 2.5 to my laptop and oggled the flashing lights!  The APM came to life.  Using Mission Planner, I looked thru a list of parameters & commands.  Mission Planner now has an ArduRover configuration, with some new commands.  Now I need to reprogram one channel to operate the Right Throttle, which comes from the RX channel 2 (normally Elevator).  Intuitively, any APM channel can be reprogrammed to do that by copying the code from APM channel 2.  APM 3 is the Elevator chanel, but I don't think that must be used; there are optional channels that might be easier to program.  But what is used to change programming in the APM channels, Arduino, Flip, what?  And where can I find the individual channel coding (I assume it's in C or C++)?  One final question:  What is Git???  Thanks for your help.  I feel a bit lost and need a clear roadmap.

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