Building an F450 quadcopter – Build Day 2 – Pairing the TX/RX

With all the parts finally on hand I found myself on a Friday evening rolling into a long weekend.  My wife was out with friends, and the kids were all occupied.  Time to make some progress!

I decided to connect the TX/RX and finish configuring the APM flight controller.  I hoped this would be a 15 minute procedure.  It wasn’t.

No Roll Values

No Roll Values

I plugged in the 5 connections between the RX and the APM, paired the remote and started the calibration.  Everything worked except roll (the input used to steer the craft) which behaved as though it wasn’t connected at all.

I Googled, asked on the Quadcopters page on FB (a great bunch of people), and read the TX manual again but I couldn’t find any reference to the situation anywhere.  I was really starting to wonder if I had a dud transmitter and would be looking forward to the hassle of boxing it up and shipping it back.

After taking some time to reflect (a.k.a sulking) I decided to break things down piece by piece.  

First, I found a setting on the TX that showed the values being put out by the controls.  That convinced me that it wasn’t a problem with the stick not functioning as I could see the values changing on all axis.

Now With Roll

Now With Roll

Next I tried unplugging all the connections and adding them back one at a time, each time shutting everything down (software and hardware) and restarting.

When I added the 3rd connection things started working including the roll value!  By the time I added the 5th channel everything worked.  I have no idea why it didn’t work before but I’ll take it.


Sadly all this messing around was a time vampire and my wife would be home any second.  I used the little remaining time to set up an area in the basement ready for the big weekend build and called it a night.

Getting Ready

Getting Ready!

This was the first time I had taken all the parts out of the box and there was good news and bad news.  The good news was that the kit unexpectedly contained a battery strap.  The bad news was that it came with no instructions what so ever.

I still had a ton of unanswered questions.  What is the best way to power the APM?  Should I program the remote to cut the inputs to make first flights easier?  Did I even know how to do that?  Should I mount the APM in the middle (closer to CoG and out of the way) or on the top so that it was easily accessible?

In addition, my plans of building this with my daughter were thwarted by her busy social schedule.

Clearly this project was going to take longer to complete than I had anticipated.  

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1 Comment

Filed under Building Multirotors, Drones, Education, Technology

One response to “Building an F450 quadcopter – Build Day 2 – Pairing the TX/RX

  1. Seems as though I’m not the only one who had a problem with the roll value not working…and then starting to work after fiddling for no apparent reason. Here’s a quote from someone else that had the same problem and posted on the Quadcopters space on FB.

    “When the problem showed up, i tested the RX channel with a servo and it works so it had to be something between the RX and the APM. I tried every possible combination connections between the RX and the APM. Despite the instructions to the contrary, i put rx output and APM inputs on channel 123 signal only, 4 and 5 vertical plug, 678 signal only. test radio calibration actually moved the limit bars (red lines) even though it did not show the green bar moving (Bizarre). saved settings, rebooted the apm 2 times, then tried with the radio link (telemetry radio for Mavlink) and THIS time it’s all working. There is a possibility that God intervened or the string of expletives conjured up some good luck, But it’s working now. There is no logical explanation for how or why. Perhaps there is some some sort of counter built in that requires you to try a certain number of times. all i can say is FINALLY !!!! “

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