Hi all,

I'm using a Turnigy Trust 55A ESC (well, trying to use) ESC.


Using my O-Scope, I can see the PWM output of the APM2, and it's 490 hertz or so, but the pulse widths are the same as the receiver output which is 49 hertz or so.

The difference is the frequency, the pulse widths are nearly the same throughout the range.

My problem is that if I connect the ESC directly to the receiver, it works fine.  But connected to the APM2, the ESC's just play this one repeating musical note at about 10 hertz.  A very annoying musical composition to say the least, plus it doesn't work!

I can see the output of the APM2, other than the frequency, it's the same as the output of the receiver.

So it looks to me like the APM2 isn't compatible with the Turnigy Trust ESC's. 

Is there a solution to this problem?

Dan Gray

P.S.  this will be my 3rd set of ESC's for this machine.....

Here's my history of ESC's.  First I purchased 50 amp RedBricks from hobby king.  I tested one alone, and was able to get 2.5 LBS of thrust from one motor.  

The moment I connected the 4 ESC's PWM wires together on the APM2, Not a peep came from these RedBrick ESC's, they all completely stopped responding in all respects.  They are DEAD, no beeps, nothing.  I went on the HobbyKing Website, and looked at the reviews, and almost everyone had problems with them.

I was in a hurry, I purchased from a local hobby shop, some 35A Swift SkyRC ESC's, and installed those.  These worked, but they have an AutoZero "feature" that makes them Beep Slowly ALL THE TIME, unless you're actually spinning the motors!  

My solution was to change the firmware 2.7.3 to put out a slightly higher PWM when APM2 wasn't enabled.  This made the beeps only happen when the APM2 was enabled.  This allowed me to use the swift ESC's.  But they only provided 1.7 LBS of thrust, so I wanted to change them.  Also, two of them failed during configuration!  Had to make another trip and buy more from the hobby shop.

So, now there's THREE ESC's that I simply DO NOT LIKE!

Ok, I looked at the Turnigy's, and checked the reviews, they seemed fine.  But now I have this third problem as described above, and I'm really frustrated.  I want to fly my new machine!

Any help would be appreciated.

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Are you plugging the ESC's into the APM or into a Power Distribution Board?

The reason I ask is I have this problem with some OS ESC's in that they will just sit there if I use the PDB but will operate if I them directly into the APM.


Thanks Mike
I was (still am) plugging the ESC's into the APM.

 I did solve the problem using the 2.7.3 code.  I found the sweet
frequency is 433 hz.  It will take that, but it won't take 444 hz!
In addition to that, I found that if you slow the frequency down AFTER
you've given it a higher freq, it won't work either.

So, First, I used mission planner to change the freq from 490 to 120.
The frequency change did work, it was 120 hz after this, but the
problem was still there.

During initialization, it starts out at about 50 hz (40,000 for ICR1,
ICR3, and ICR4).  Then it must be switched to the standard 490 hertz
briefly until the configuration is read, then goes down to 120 hz.
The ESC likes 120 herts, but NOT if you use 490 hertz for a brief
moment!  Weird!

But once I changed my configuration back to 490 hertz using mission
planner, and then made the value of ICR1, 3, and 4 be >= 4600 (max 433
hz) it works fine.

So, there's only one line of code to change in my case, as well as
being sure the configuration is set for 490 hertz.

In APM_RC_APM2.cpp, I added one line in
void APM_RC_APM2::SetFastOutputChannels(uint32_t chmask, uint16_t speed_hz)

Existing line:
    uint16_t icr = _map_speed(speed_hz);

New line after Existing line:
    if(icr < 4600) icr = 4600;  //DPG

And this solved the problem.

I think they're trying to make the ESC's sooo smart these days that it
screws up anything other than a regular receiver.  They don't test
these with an APM or anything!

Well, at least I'll be able to use the new ESC's.

Thanks again everybody.


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