A little debug help please?

Info and Discussion about the ESC32 hardware and software

A little debug help please?

Postby Wingspinner » Thu Aug 30, 2012 10:06 pm

Ok, one of my ESC32s stopped working.After some troubleshooting I've found that the ESC32 works fine when in UART as input but not PWM. Without schematics I'll have to do more work to find the problem but perhaps Jussi or Paul or Bill can answer a couple of questions for me. First, is there some sort of protection on the PWM input line to protect the processor pin or does it go directly to the processor? Second, what pin is it? From the sources it says GPIO_PIN_8 on GPIOA. That says to me pin 29 on the processor. Is that correct? There isn't a PWM signal coming in on that pin.

Some quick confirmation on the physical pin number and the circuitry between the PWM input and the pin would be very helpful.

Thank you!
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Re: A little debug help please?

Postby Kisssys » Fri Aug 31, 2012 12:05 am

Their is a direct connection to Pin 29 for PWM input.

Have you tried to reflash it?
Steve
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Re: A little debug help please?

Postby Wingspinner » Fri Aug 31, 2012 1:10 am

Kisssys wrote:Their is a direct connection to Pin 29 for PWM input.

Have you tried to reflash it?



Hi Steve,
Yes, re-flashed it. However, I've another symptom, pin 29 only has 4.1 ohms to ground - either polarity. I've gone over the board with a high-powered magnifier and can see nothing that looks like a short so I can only conclude that processor pin has failed.

When I add the fact in that my newest AQ FC board failed on the same pin (M13)that ESC32 was on at approximately the same time I can't help but think it's related. It's very strange because it was a working copter prior to swapping out my older AQ FC for the new one.

Anyhow, it's kind of a bummer - I've got an AQ FC and an ESC32 that have never flown with bad processors. Given that they both went out with the same type of failure at about the same time I can't help but feel something on my power distribution board must have caused it. It's too much of a coincidence to think it's an infant mortality issue so I can't, in good conscious ask Paul or Jussi to replace the two items. I have SMD re-work equipment and can probably repair the ESC32 myself but haven't worked with such a fine pin pitch as is the processor on the AQ FC. Hmmm, some thought required here.

Cheers,
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Re: A little debug help please?

Postby Kisssys » Fri Aug 31, 2012 1:32 am

Yes, it does sound related and that pin is definitely shorted with that low a resistance. You could take a pin and lift it up to prove the point I guess. The hard part is figuring out what went wrong.

It could have been as simple as unplugging the device with power applied which I'm guilty of, or static.

I'd rework the ESC as you have little to lose, and just use a different pin out of the FC board. The chips have bootloaders built in so you still don't need a programmer.

I rework a lot of stuff but if I didn't have a Stereo Microscope I'd never get the job done. I've taken the 32f4xx off with just hot air and no preheat with the right attachment.

It has also has been changed using just Chip Quik http://www.digikey.com/product-detail/e ... ND/1164266 which works pretty well.
Steve
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Re: A little debug help please?

Postby Wingspinner » Sun Sep 02, 2012 3:05 pm

I'm pretty sure what took out the m13 pin on the processor. My power distribution board also conveniently routes the control signals to the ESC as well as power the ESC plugs into it and so does the FC. Makes for tidy wiring. What appears happened is the connector for the FC may have been plugged in one pin offset such that power and ground from the distribution board may have been connected to m13 and power on the FC. The connection is between the.airframe main frame members and hard to see. Not sure but that may have been it. Not sure why that
Oils affect the ESC32 though.

Anyway, processors and hot air nozzles on order from divinely. I don't have a stero microscope but I do have a very high magnification headset which will be sufficient n

Btw I was also thinking I could just chang the Pwm input on the ESC32 in both hw and SE. That ESC would.always need that special version though.

Thanks for your help. I'll let you know how it goes.

Regards
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Re: A little debug help please?

Postby bn999 » Sun Sep 02, 2012 3:44 pm

I rarely need to resort to hot air anymore when replacing the MCU. I'd highly recommend trying Chip Quick first, especially if you have little experience with hot air.

The only requirement for the PWM IN pin is that it is a timer pin that can handle input capture. Not sure if there are any more of those available.
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Re: A little debug help please?

Postby Wingspinner » Sun Sep 02, 2012 9:13 pm

Hi Bill,
I've never used the Chip Quick stuff. I'll give it a look. I could just use another input. Heck, it's got plenty but it's my perfectionism showing....

Regards,
Ron
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Re: A little debug help please?

Postby Wingspinner » Mon Sep 03, 2012 3:59 pm

Update, well, a little more troubleshooting.

I've verified that the ESC32 STM32F103 pin 29 is damaged and will need a new processor - not difficult. More importantly, I found a tiny solder particle shorting the AQ6 processor pin that connects to M13. Cleaned that out and wa-la, it works ok now - no need to repair the AQ6 board!
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Re: A little debug help please?

Postby joebar.rc » Mon Sep 03, 2012 4:05 pm

Perfect, good job.
I also swapped an ESC32 mcu, only the 3rd swap I ever did. With some chipquik it's easy to remove and clean.
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Re: A little debug help please?

Postby Wingspinner » Sat Sep 08, 2012 11:48 pm

Wingspinner wrote:Update, well, a little more troubleshooting.

I've verified that the ESC32 STM32F103 pin 29 is damaged and will need a new processor - not difficult. More importantly, I found a tiny solder particle shorting the AQ6 processor pin that connects to M13. Cleaned that out and wa-la, it works ok now - no need to repair the AQ6 board!


Ok, I have to correct myself. After using the ChipQuik method I removed the processor and put in a new one. OUCH! it didn't fix the problem. New one behaves just like the old one. I'm thinking, "what the heck is going on". So I checked the old processor and it was, in fact damaged - low resistance between pin 29 and ground. I bite the bullet and take off the second processor. I check it off the board and it's not damaged. So, it's something on the board and here's what I found:

esc32_failure_cause.jpg
ESC32 Failure Cause


What you are looking at is the area around the PWM input pads on the ESC32. The way the board is designed is the outer board layer is the typical practice of a ground plane with cut-outs for other pads or components. In the case the cutouts are there for the PWM inputs but the separation can't be more than a 1/10 of a mm - maybe less. Plus, on the side toward the edge the ground plan is also, maybe a 1/10 of a mm and in a place where it's likely the PWM wires can rub against it. In my case, apparently the resist got chipped off and when the wires were soldered on it the PWM wire was soldered to ground through that very tiny copper strip.

Had nothing to do with my power distribution board. What I don't understand is how the first processor was damaged when, in fact, it was a problem of shorting the pwm input to ground. Don't know but somehow I damaged the new processor trying to put it on a second time (or it got damaged in removing it) So now I need to order yet another processor. Bummer!

Anyway, I recommend to Bill or whoever is responsible for that board design to modify it ever so slightly by removing that very tiny section of the ground plane between the PWM pins and the edge of the board.
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