3rd CFX board with no swing sounds

[LuxKota]

I've had 3 CFX boards that have done the same thing: constant swing/clash sounds and then no swing sounds. I updated the board to the latest software, but that has not fixed it. I have double checked the wiring and its all where it should be. I have installed 30+ of these boards and this issue seems to be with my most recent purchased boards. Is there a known issue with this board?

[AngelOmega]

I just recently posted an identical issue. Mine turned out to be a bad motion sensor. You say you’ve installed over 30 boards, so I’m going to guess you probably know to take standard precautions against ESD. Erv has said something about a bad batch of capacitors they received, as well as that the board works without said capacitor, though it isn’t as safe for the board. I’m curious if maybe this batch of CFX boards are just ultra-sensitive to ESD? Perhaps our typical ESD prevention has been nullified by some very sensitive motion sensors.

[LuxKota]

I figured it could of been ESD after the first board, so when I installed the replacement board I took extra preventative steps. After the second board did the same thing, I started suspecting something else was going on. The 3rd board pretty much confirms it. The way all 3 boards worked fine for some time and then ended up not working in the same exact way leads me to believe that it's a hardware issue. I just need to know if it's something I can fix, because this is starting to cost me a lot of time and money.

[K-2SO]

I would shoot Chewbacca a PM regarding this. 

[LuxKota]

Will do, thank you!

[erv]

yes, those will be taken under warranty if needed to

[scott]

Is there a better way to contact Chewbacca besides PM?  I also experienced this issue and sent a PM about a week ago but have not heard back. Sounds like if the ones reported on this forum a any indicator, he could have his hands full!

[erv]

I directly PM michael to have him aware of possible full inbox and the discussion here.

I'm just back from the mountains and while I took my dev board and kit with me + a saber, I didn't have a chance to work on one of the 3 faulty boards that were sent to me for analysis.
We came back this morning (night drivers, reached destination at 4AM) and I'm using some time today to work on this. So far, here are my findings :

- It seems rather "new". We had very very few issues reported with our France based manufacturing and same for the initial USA manufacturing, the latest TCSS batch seems to display more of this and I'm not putting the blame on the customer "just because", even if something clearly affects the motion sensor. We also got 2 cases reported on CF9 of the latest production (they use the same sensor), so I'm not excluding that some of our sensors got a silicon die revision or something wacky concerning them. Not dodging any bullet here (see fix below) but I think extra care should be taken regarding ESD in any case.


- I finally have the "reason" of the symptoms (but not necessarily the cause): the gyro capacitor (currently marked 14V in the user's manual voltage map) doesn't regulate at the right voltage. I stood corrected after someone said it's 14V (on his/her... faulty board) while, after testing a bunch of ok boards, it is 9V (ish). I've corrected the next revision of the manual I'll release with the next firwmare.

- I studied the sensor soldering, zero issues, the manufacturing is spot on, no cold solder, confirmed by the fact the digital communication with the sensor finds it (in the logs) and initializes it just fine

- when the gyro is enabled, its high voltage charge pump, buffered by the gyro capacitor, is activated and should gently ramp to 9V ish. On faulty boards, looking at the oscilloscope, it rises much faster than on a working board/sensor and doesn't regulate, and goes to the roof instead. This leads to either a sensor stuck in noise level (close to zero values, almost not changing, in the 100's vs. +/- 32768 range) and sometimes with a noisy accel.

- touching the gyro cap (or changing it) sometimes fixes the problem but in some cases not permanently. Touching it (with the fingers) helps its internal regulator to stabilize again around the expected 9V.


Bottom line : those boards / sensors do pass the tests but get damaged along the way. Just like the aux switch pad gets damaged with ESD (leading to the destruction of its internal pullup) the gyro high voltage pump charge seems to have its damper (load) resistor damaged leading for the motion sensor to not be able to regulate the voltage. The capacitor or its value aren't concerned and replacing with identical doesn't change the issue most of the time. However, replacing the (dead) internal load resistor works.

We've been able to revive dead boards the following way :
- remove the gyro capacitor. Not great of course, no regulation and noisy reference but in practice, makes the gyro working again but not ideal
- add 1Mohm resistor in parallel of the capacitor (solder on top), that will replace the damaged damper load from the sensor and ensure convergence (and proper rising) of the regulated voltage.


I've tried many different things to see if that could be fixed / patched software side : no dice. I sequentially applied the configuration of the motion sensor, ending (after some long pauses & delay) with the enabling of the gyro, it leaves power down / low power mode, enables its charge pump and fails to regulate to the expected 9V. Put the missing (internal) load, works again.

So, it could be just the motion sensor to be off specs concerning the charge pump. Still they work first place, and board will get damaged later on. We might just end putting a smaller value capacitor but that's less noise protection for the gyro and not really satisfactory if it's the tree hiding the forest. Again it's not a general problem on all sensors or boards, just a few, possibly on a specific batch (manufacturing or supplies)

[scott]

Thank you for all of that context Erv. I am definitely not complaining as I have installed 25 (at least 5 CFX) and never had an issue. Certainly don’t want your skills directed away from the new features and innovation!

I have always taken ESD precautions but tightened them up even more after this topic began. I have been looking for a micro usb with extra protection, but have not been successful. The only real change recently was lots of hooking up to RICE and serial logs. Any tricks to ensure ESD is not introduced when connecting to the USB port?  I have been touching the end of the wire to my ground in the absence of a better idea.

As always, anything that I can do to be helpful/part of the solution, and I’m in!

[sacubitril]

I also had posted about a lack of swing sounds with a recently acquired CFX. I purchased some capacitors but had not replaced it yet as I was waiting for a hot air solder and solder paste. However, the sound board started playing swing sounds again. Rarely, it will play continuous swing sounds randomly.

I was wondering if people would recommend adding a resistor in parallel, replacing the capacitor with a new one, removing the existing capacitor, waiting till it fails again before taking action, or get in touch with chewbacca?